BASIC ELECTRONICS ENGINEERING 1
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 01 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Passive Components
AIM Study of Passive components ndash Resistors Capacitors Inductors Relays Switches
Transformers Connectors
PREREQUISITE
Knowledge of active components
Knowledge of passive components
Difference between active and passive components
OBJECTIVE
Types and subtypes of passive components
Applications of passive components
COMPONENTS
1) Resistors 2) Capacitors 3) Inductors 4) Relays 5) Switches 6) Transformers
7) Connectors
THEORY
Resistor
A resistor is a two terminal electronic component that produces a voltage across its terminals that is
proportional to the electric current through it in accordance with Ohmlsquos law
V = I R
Where V = Voltage across resistor
I = Current flowing through resistor
R = Resistance of the resistor
Resistor having the physical material which resists the flow of electric current to some extent is
called as resistor Resistors are circuit element having function of offering electrical resistance in
circuit The resistance of a material with length llsquo and area Alsquo is given by
R= ( l) A
Where is the resistivity
Classification of Resistor
A) Fixed Resistor Fixed resistor are classified into 4 types based on various factors like
manufacturing style resistance range power rating etc
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1) Carbon composition
2) Carbon film
3) Metal film (Thick and Thin film type)
4) Wire-wound (Power and Precision style type)
Symbol of Fixed Resistor
B) Variable Resistor Variable type resistor are used in electronic circuits to adjust the value
of voltages and currents For example it used in Television as volume control brightness
control etc There are three types of variable resistor
1) Potentiometer
2) Rheostat
3) Trimmer
Symbol of Variable resistor
Types of Fixed resistor
1) Carbon composition resistors
It is the most common type as they are cheap general purpose resistor Their resistive element is
manufactured from a mixture of finely ground carbon dust or graphite (similar to pencil lead) and
non-conducting ceramic (clay) powder to bind it all together
Carbon composition resistors are low to medium power resistors with low inductance which makes
them ideal for high frequency application but they can also suffer form noise and stability when
heat is dissipated in temperature
2) Carbon film and Metal film resistors
They are generally made by depositing pure metals such as nickel or an oxide film tin-oxide onto
an insulating ceramic rod or substrate
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The resistive value of the resistor is controlled by increasing the desired thickness of the film and
then by laser cutting a spiral helix groove type pattern into this film It has much better temperature
stability low noise and is generally better for high frequency or radio frequency applications
3) Wire wound resistors-
Wire wound resistor is made by winding a thin metal alloy wire (Nichrome) or similar wire onto on
insulating ceramic former in the form of a spiral helix similar to the film resistors These types of
resistors are generally only available in very low ohmic high precision values (from 001 to
100Kohm) due to gauge of the wire and number of turns possible on the former making them ideal
for use in measuring circuits and Wheatstone bridge type applications
Types of Variable resistor
1) Potentiometer
A potentiometer (colloquially known as ―pot) is a three terminal resistor with sliding contact that
forms an adjustable voltage divider
Where A and B fixed terminals
W is the variable terminal
2) Rheostat
The most common way to vary the resistance in a circuit is to use a variable resistor or a rheostat
A rheostat is two terminal variable resistors
Symbol of Rheostat Actual picture of Rheostat
They are designed to handle much higher voltage and current Typically these are constructed as a
resistive wire wrapped to form a toroid coil with the moving over the upper surface of toroid
sliding from one turn of the wire to next
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3) Trimmer
A trimmer is a miniature adjustable electrical component It is called trimmer potentiometer or
trimpots
Actual pictures of the trimmers
How to calculate the value of fixed resistor using colour code
There are four color bands which are painted on resistors First band indicates first digit second
band indicate second digit and third band indicates the decimal multiplier
1st color band First digit
2nd
color band Second digit
3rd
color band Decimal multiplier
4th color band Tolerance
By using following table we can calculate the fixed resistors values
Capacitor
An electric circuit element which is used to store charge temporarily consisting in general of two
metallic plates (conductors) separated and insulated from each other by a dielectric Also called
condenser
Symbol of Capacitor
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When a voltage potential difference exists between the conductors an electric field is present in the
dielectric An ideal capacitor is characterized by a single constant value capacitance which is
measured in farads This is the ratio of the electric charge on each conductor to the potential
difference between them
Capacitors are widely used in electronic circuits to block the flow of direct current while allowing
alternating current to pass to filter out interference to smooth the output of power supplies and for
many other purposes They are used in resonant circuits in radio frequency equipment to select
particular frequencies from a signal with many frequencies
Types of Capacitors
A) Fixed Capacitors Types of fixed capacitors are
1) Electrolytic capacitors Aluminum Electrolytic Capacitors are polarized and can be used in DC
circuits Typical values range form 01uF to 68000uF Ideal for use in filtering and smoothing
applications in power supplies Also used for coupling and bypassing in audio circuits and as a
timing element in non-critical circuits They have a high reliability and low leakage
2) Paper capacitor In these paper is used as dielectric They are used for high voltage and high
current applications Sometimes on surface of paper vapors deposition of Zn or Al metal is made to
avoid separate winding of metal foil and paper
3) Mica Capacitor Natural mica has significant advantages It is inert It will not change
physically or chemically with age and hence good temperature ability
a) Small mica capacitor
b) Transmitting mica capacitors
4) Glass Capacitor It is stable durable and practically immune to temperature aging voltage
moisture vibrations Aluminum foil is used glass is drawn to 1mm thick flexible layers of foil are
interleaved and then leads are attached Then assembly is fused at high temperature
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5) Ceramic Capacitors These are manufactured in many shapes and sizes depending on
applications Dielectric material for this capacitor is high temperature sintered inorganic
compound
Types of Ceramic capacitors are
1] Disc ceramic capacitors
2] Tubular ceramic capacitors
3] Monolithic Ceramic Capacitors
4] Button Cart wheel door knob ceramic capacitors
6) Aluminum Electronic Capacitors These are electro chemical devices Two aluminum foils
separated by insulting papers are wound into cylinder The roll is impregnated with liquid
electrolyte stabilized
Other types of electrolytic capacitors are
1] Tantalum electrolytic capacitors
2] Tantalum foils electrolytic capacitors
3] Wet slug Tantalum capacitors
4] Solid electrolyte Tantalum capacitors
B) Variable Capacitors
Variable capacitors are mostly used in radio tuning circuits and they are sometimes called tuning
capacitors having very small capacitance values typically between 100pF and 500pF
(100pF = 00001microF)
Actual pictures of variable capacitor and trimmer with its symbols respectively
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How to calculate the value of Capacitor using number coding and colour coding
Most capacitors have numbers printed on their bodies to indicate their electrical characteristics
Some are indicated with XYZ JKM VOLTS V where XYZ represents the capacitance (calculated
as XY x 10Z) the letters J K or M indicate the tolerance (plusmn5 plusmn10 and plusmn20 respectively) and
VOLTS V represents the working voltage
Example
A capacitor with the following text on its body
105 K 330 V has a capacitance of 10 x 105 pF = 1microF (plusmn10) with a working voltage of 330 V
A capacitor with the following text
473 M 100 V has a capacitance of 47 x 103 pF = 47 nF (plusmn20) with a working voltage of 100 V
A number code is often used on small capacitors where printing is difficult
The 1st number is the 1st digit
The 2nd number is the 2nd digit
The 3rd number is the number of zeros to give the capacitance in pF
Ignore any letters - they just indicate tolerance and voltage rating
For example 102 means 1000pF = 1nF (not 102pF)
For example 472J means 4700pF = 47nF (J means 5 tolerance)
It can be difficult to find the values of these small capacitors because there are many types of them
and several different labeling systems
Many small value capacitors have their value printed but without a multiplier so
you need to use experience to work out what the multiplier should be
For example 01 means 01microF = 100nF
Sometimes the multiplier is used in place of the decimal point
For example 4n7 means 47nF
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Color coding
Sr No Color Significant
digits
Multi-
pliers
Capacitance
tolerance
Characte
r-eristic
DC
working
voltage
Operating
temperature
1 Black 0 1 plusmn20 mdash mdash minus55 degC to +70
degC
2 Brown 1 10 plusmn1 B 100 mdash
3 Red 2 100 plusmn2 C mdash minus55 degC to
+85degC
4 Orange 3 1000 mdash D 300 mdash
5 Yellow 4 10000 mdash E mdash minus55 degC to
+125degC
6 Green 5 mdash plusmn5 F 500 mdash
7 Blue 6 mdash mdash mdash mdash minus55 degC to
+150 degC
8 Violet 7 mdash mdash mdash mdash mdash
9 Grey 8 mdash mdash mdash mdash mdash
10 White 9 mdash mdash mdash mdash mdash
11 Gold mdash mdash plusmn05 mdash 1000 mdash
12 Silver mdash mdash plusmn10 mdash mdash mdash
Or plusmn05 pF whichever is greater
A color code was used on polyester capacitors for many years The colors should be read like the
resistor code the top three color bands giving the value in pF Ignore the 4th band (tolerance) and
5th band (voltage rating)
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For example
Brown black orange means 10000pF = 10nF = 001microF
For example
Wide red yellow means 220nF = 022microF
(Note that there are no gaps between the color bands so 2 identical bands
actually appear as a wide band)Inductor
An inductor or a reactor is a passive electrical component that can store energy in a magnetic field
created by the electric current passing through it An inductors ability to store magnetic energy is
measured by its inductance in units of henries Typically an inductor is a conducting wire shaped
as a coil the loops helping to create a strong magnetic field inside the coil due to Faradays Law of
Induction Inductors are one of the basic electronic components used in electronics where current
and voltage change with time due to the ability of inductors to delay and reshape alternating
currents
Symbol of fixed inductor
Types of Inductor
1) Iron core Inductor This classification includes chokes and transformers both of which have
laminated iron cores A choke is a single winding and a transformer has two or more windings
Typical values of inductance for chokes range from 01 of a Henry to 50 henries Lamination
decreases eddy current losses
b) Air core Inductor It consists of number of turns of wire wound on a former made of cardboard
Since air is inside the former the inductor is called as air core inductor The only adjustment
available with air core inductors is by tapping all or part of a turn or by varying the spacing
between turns
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c) Ferrite core Inductor By inserting a ferrite or iron dust core in a coil it is possible to double its
inductance If the core is threaded its position within the coil can be varied to alter the inductance
This type of coil is used throughout the HF range and into the VHF for low-level signal circuits
Losses in the cores make them unsuitable for use in power circuits Values range from a few micro
henries to about a milli Henry
How to calculate the value of Inductor using color code
Some Radio Frequency chokes have their values indicated by a color code similar to that of
resistors
Applications
Filter chokes are used in smoothing pulsating current in rectifier Audio frequency chokes
are used to provide high impedance to audio frequencies Radio frequency chokes are used to block
the radio frequencies in communication systems
Switches
The term switch typically refers to electrical power or electronic telecommunication circuits In
applications where multiple switching options are required (eg a telephone service) mechanical
switches have long been replaced by electronic variants which can be intelligently controlled and
automated
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In the simplest case a switch has two pieces of metal called contacts that touch to make a circuit
and separate to break the circuit
There are different types of standard switches used in electronics
Type of Switch Circuit Symbol Example
1) ON-OFF Single Pole Single Throw =
SPST - A simple on-off switch Such
switches can be used to switch the power
supply to a circuit
SPST toggle switch
(ON)-OFF Push-to-make = SPST
Momentary - A push-to-make switch
returns to its normally open (off) position
when you release the button this is shown
by the brackets around ON This is the
standard doorbell switch
Push-to-make switch
ON-(OFF) Push-to-break = SPST
Momentary- A push-to-break switch
returns to its normally closed (on) position
when you release the button
Push-to-break switch
2) ON-ON Single Pole Double Throw =
SPDT - This switch can be on in both
positions switching on a separate device
in each case It is often called a
changeover switch A SPDT toggle
switch may be used as a simple on-off
switch by connecting to COM and one of
the A or B terminals shown in the
diagram
ON-OFF-ON SPDT Centre Off- A
special version of the standard SPDT
switch It has a third switching position in
the centre which is off Momentary (ON)-
OFF-(ON) versions are also available
where the switch returns to the central off
SPDT toggle switch
SPDT slide switch
(PCB mounting)
SPDT rocker switch
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position when released
3) Dual ON-OFF Double Pole Single
Throw = DPST- A pair of on-off switches
which operate together DPST switch is
often used to switch mains electricity
because it can isolate both the live and
neutral connections
DPST rocker switch
Dual ON-ON Double Pole Double
Throw = DPDT- A pair of on-on switches
which operate together (shown by the
dotted line in the circuit symbol) A DPDT
switch can be wired up as a reversing
switch for a motor as shown in the
diagram
ON-OFF-ON DPDT Centre Off -
A special version of the standard SPDT
switch It has a third switching position in
the centre which is off This can be very
useful for motor control because you have
forward off and reverse positions
Momentary (ON)-OFF-(ON) versions are
also available where the switch returns to
the central off position when released
DPDT slide switch
Wiring for Reversing
Switch
Special Switches
Type of Switch Example
1) Push-Push Switch (eg SPST = ON-OFF) - This looks like a
momentary action push switch but it is a standard on-off switch
push once to switch on push again to switch off This is called a
latching action
2) Micro switch (usually SPDT = ON-ON)-Micro switches are
designed to switch fully open or closed in response to small
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movements They are available with levers and rollers attached
3) Key switch - A key operated switch The example shown is
SPST
4) Tilt Switch (SPST) - Tilt switches contain a conductive liquid
and when tilted this bridges the contacts inside closing the
switch They can be used as a sensor to detect the position of an
object
5) Reed Switch (usually SPST) - The contacts of a reed switch
are closed by bringing a small magnet near the switch They are
used in security circuits for example to check that doors are
closed Standard reed switches are SPST (simple on-off) but
SPDT (changeover) versions are also available
6) DIP Switch (DIP = Dual In-line Parallel) - This is a set of
miniature SPST on-off switches the example shown has 8
switches The package is the same size as a standard DIL (Dual
In-Line) integrated circuit This type of switch is used to set up
circuits eg setting the code of a remote control
7) Multi-pole Switch - The picture shows a 6-pole double throw
switch also known as a 6-pole changeover switch It can be set
to have momentary or latching action Latching action means it
behaves as a push-push switch push once for the first position
push again for the second position etc
8) Multi-way (Rotary) Switch - Multi-way switches have 3 or
more conducting positions (Several poles contact sets) A
popular type has a rotary action and it is available with a range of
contact arrangements from 1-pole 12-way to 4-pole 3 way
Multi-way rotary switch
1-pole 4-way switch symbol
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9) Tactile Switch
These switches used in instruments keyboards
Connectors
An electrical connector is a conductive device for joining electrical circuits together The
connection may be temporary as for portable equipment or may require a tool for assembly and
removal or may be a permanent electrical joint between two wires or devices Connectors may join
two lengths of flexible wire or cable or may connect a wire or cable to an electrical terminal
There are hundreds of types of electrical connectors Out of that some of the connecters given
below
1) Battery clips and holders
The standard battery and battery holders such as the 6 times AA cell holder shown Battery holders are
also available with wires attached with pins for PCB mounting or as a complete box with lid
switch and wires
2) Terminal blocks and PCB terminals
Terminal blocks are usually supplied in 12-way lengths but they can be cut into smaller blocks with
a sharp knife large wire cutters or a junior hacksaw They are sometimes called chocolate blocks
because of the way they can be easily cut to size PCB mounting terminal blocks provide an easy
way of making semi-permanent connections to PCBs
PCB Terminal block
terminal
block
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3) Crocodile clips
The standard crocodile clip has no cover and a screw contact However miniature insulated
crocodile clips are more suitable for many purposes including test leads
Crocodile clips
4) 4mm plugs sockets and terminals
These are the standard single pole connectors used on meters and other electronic equipment They
are capable of passing high currents (typically 10A) and most designs are very robust
Plugs
Plugs may have a screw or solder terminal to hold the cable
Sockets
these are usually described as panel mounting because they are designed to be fitted to a case
Terminals
In addition to a socket these have provision for attaching a wire by threading it through a hole (or
wrapping it around the post) and tightening the top nut by hand
4mm terminal and solder tag
5) DC power plugs and sockets
These 2-pole plugs and sockets ensure that the polarity of a DC supply cannot be accidentally
reversed The standard sizes are 21 and 25mm plug diameter Standard plugs have a 10mm shaft
long plugs have a 14mm shaft
6) Jack plugs and sockets
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These are intended for audio signals so mono and stereo versions are available The sizes are
determined by the plug diameter frac14 (63mm) 35mm and 25mm The 25mm size is only
available for mono
frac14 (63mm) jack plug and socket 35mm jack plug and socket 35mm jack line socket
(for fitting to a cable)
35mm jack plug and socket connections
(the R connection is not present on mono plugs)
L = left channel signal R = right channel signal COM = common (0V screen) (Do not use jack
plugs for power supply connections because the contacts may be briefly shorted as the plug is
inserted Use DC power connectors for this)
7) Phono plugs and sockets
These are used for screened cables carrying audio and video signals Stereo connections are made
using a pair of phono plugs and sockets
8) Coax plugs and sockets
These are similar to the phono plugs and sockets described above but they are designed for use with
screened cables carrying much higher frequency signals such as TV aerial leads They provide
better screening because at high frequencies this is essential to reduce electrical noise
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Construction of a screened cable
9) BNC (Bayonet Neill-Concelman) plugs and sockets
These are designed for screened cables carrying high frequency signals where an undistorted and
noise free signal is essential for example oscilloscope leads BNC plugs are connected with a push
and twist action to disconnect you need to twist and pull
Plugs and sockets are rated by their impedance (50 or 75 ) which must be the same as the
cables impedance
11) D connectors
These are multi-pole connectors with provision for screw fittings to make semi-permanent
connections for example on computer equipment The D shape prevents incorrect connection
Standard D-connectors have 2 rows of contacts (top picture) 9 15 and 25-way versions are the
most popular
12) IDC communication connectors
These multi-pole insulation displacement connectors are used for computer and
telecommunications equipment They automatically cut through the insulation on wires when
installed and special tools are required to fit them They are available as 4 6 and 8-way versions
They are called BT (British Telecom) connectors
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13) USB Connector
The Universal Serial Bus is a serial bus standard to interface devices founded in 1996
Relays
A relay is an electrically operated switch Current flowing through the coil of the relay creates a
magnetic field which attracts a lever and changes the switch contacts The coil current can be on or
off so relays have two switch positions and they are double throw (changeover) switches Relays
allow one circuit to switch a second circuit which can be completely separate from the first For
example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit There is
no electrical connection inside the relay between the two circuits the link is magnetic and
mechanical
Following figure shows a working of relay with its coil and switch contacts You can see a
lever on the left being attracted by magnetism when the coil is switched on This lever moves the
switch contacts There is one set of contacts (SPDT) in the foreground and another behind them
making the relay DPDT
Circuit symbol for a relay Picture of a relay
The relays switch connections are usually labeled COM NC and NO
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COM = Common always connect to this it is the moving part of the switch
NC = Normally Closed COM is connected to this when the relay coil is off
NO = Normally Open COM is connected to this when the relay coil is on
Connect to COM and NO if you want the switched circuit to be on when the relay coil is
on
Connect to COM and NC if you want the switched circuit to be on when the relay coil is
off
Advantages of relays
Relays can switch AC and DC transistors can only switch DC
Relays can switch high voltages transistors cannot
Relays are a better choice for switching large currents (gt 5A)
Relays can switch many contacts at once
Disadvantages of relays
Relays are bulkier than transistors for switching small currents
Relays cannot switch rapidly (except reed relays) transistors can switch many times per
second
Relays use more power due to the current flowing through their coil
Relays require more current than many ICs can provide so a low power transistor may
be needed to switch the current for the relays coil
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductorsmdashthe transformers coils A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic field
through the secondary winding This varying magnetic field induces a varying electromotive force
(EMF) or voltage in the secondary winding This effect is called mutual induction
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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1) Carbon composition
2) Carbon film
3) Metal film (Thick and Thin film type)
4) Wire-wound (Power and Precision style type)
Symbol of Fixed Resistor
B) Variable Resistor Variable type resistor are used in electronic circuits to adjust the value
of voltages and currents For example it used in Television as volume control brightness
control etc There are three types of variable resistor
1) Potentiometer
2) Rheostat
3) Trimmer
Symbol of Variable resistor
Types of Fixed resistor
1) Carbon composition resistors
It is the most common type as they are cheap general purpose resistor Their resistive element is
manufactured from a mixture of finely ground carbon dust or graphite (similar to pencil lead) and
non-conducting ceramic (clay) powder to bind it all together
Carbon composition resistors are low to medium power resistors with low inductance which makes
them ideal for high frequency application but they can also suffer form noise and stability when
heat is dissipated in temperature
2) Carbon film and Metal film resistors
They are generally made by depositing pure metals such as nickel or an oxide film tin-oxide onto
an insulating ceramic rod or substrate
BASIC ELECTRONICS ENGINEERING 3
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The resistive value of the resistor is controlled by increasing the desired thickness of the film and
then by laser cutting a spiral helix groove type pattern into this film It has much better temperature
stability low noise and is generally better for high frequency or radio frequency applications
3) Wire wound resistors-
Wire wound resistor is made by winding a thin metal alloy wire (Nichrome) or similar wire onto on
insulating ceramic former in the form of a spiral helix similar to the film resistors These types of
resistors are generally only available in very low ohmic high precision values (from 001 to
100Kohm) due to gauge of the wire and number of turns possible on the former making them ideal
for use in measuring circuits and Wheatstone bridge type applications
Types of Variable resistor
1) Potentiometer
A potentiometer (colloquially known as ―pot) is a three terminal resistor with sliding contact that
forms an adjustable voltage divider
Where A and B fixed terminals
W is the variable terminal
2) Rheostat
The most common way to vary the resistance in a circuit is to use a variable resistor or a rheostat
A rheostat is two terminal variable resistors
Symbol of Rheostat Actual picture of Rheostat
They are designed to handle much higher voltage and current Typically these are constructed as a
resistive wire wrapped to form a toroid coil with the moving over the upper surface of toroid
sliding from one turn of the wire to next
BASIC ELECTRONICS ENGINEERING 4
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3) Trimmer
A trimmer is a miniature adjustable electrical component It is called trimmer potentiometer or
trimpots
Actual pictures of the trimmers
How to calculate the value of fixed resistor using colour code
There are four color bands which are painted on resistors First band indicates first digit second
band indicate second digit and third band indicates the decimal multiplier
1st color band First digit
2nd
color band Second digit
3rd
color band Decimal multiplier
4th color band Tolerance
By using following table we can calculate the fixed resistors values
Capacitor
An electric circuit element which is used to store charge temporarily consisting in general of two
metallic plates (conductors) separated and insulated from each other by a dielectric Also called
condenser
Symbol of Capacitor
BASIC ELECTRONICS ENGINEERING 5
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When a voltage potential difference exists between the conductors an electric field is present in the
dielectric An ideal capacitor is characterized by a single constant value capacitance which is
measured in farads This is the ratio of the electric charge on each conductor to the potential
difference between them
Capacitors are widely used in electronic circuits to block the flow of direct current while allowing
alternating current to pass to filter out interference to smooth the output of power supplies and for
many other purposes They are used in resonant circuits in radio frequency equipment to select
particular frequencies from a signal with many frequencies
Types of Capacitors
A) Fixed Capacitors Types of fixed capacitors are
1) Electrolytic capacitors Aluminum Electrolytic Capacitors are polarized and can be used in DC
circuits Typical values range form 01uF to 68000uF Ideal for use in filtering and smoothing
applications in power supplies Also used for coupling and bypassing in audio circuits and as a
timing element in non-critical circuits They have a high reliability and low leakage
2) Paper capacitor In these paper is used as dielectric They are used for high voltage and high
current applications Sometimes on surface of paper vapors deposition of Zn or Al metal is made to
avoid separate winding of metal foil and paper
3) Mica Capacitor Natural mica has significant advantages It is inert It will not change
physically or chemically with age and hence good temperature ability
a) Small mica capacitor
b) Transmitting mica capacitors
4) Glass Capacitor It is stable durable and practically immune to temperature aging voltage
moisture vibrations Aluminum foil is used glass is drawn to 1mm thick flexible layers of foil are
interleaved and then leads are attached Then assembly is fused at high temperature
BASIC ELECTRONICS ENGINEERING 6
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5) Ceramic Capacitors These are manufactured in many shapes and sizes depending on
applications Dielectric material for this capacitor is high temperature sintered inorganic
compound
Types of Ceramic capacitors are
1] Disc ceramic capacitors
2] Tubular ceramic capacitors
3] Monolithic Ceramic Capacitors
4] Button Cart wheel door knob ceramic capacitors
6) Aluminum Electronic Capacitors These are electro chemical devices Two aluminum foils
separated by insulting papers are wound into cylinder The roll is impregnated with liquid
electrolyte stabilized
Other types of electrolytic capacitors are
1] Tantalum electrolytic capacitors
2] Tantalum foils electrolytic capacitors
3] Wet slug Tantalum capacitors
4] Solid electrolyte Tantalum capacitors
B) Variable Capacitors
Variable capacitors are mostly used in radio tuning circuits and they are sometimes called tuning
capacitors having very small capacitance values typically between 100pF and 500pF
(100pF = 00001microF)
Actual pictures of variable capacitor and trimmer with its symbols respectively
BASIC ELECTRONICS ENGINEERING 7
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How to calculate the value of Capacitor using number coding and colour coding
Most capacitors have numbers printed on their bodies to indicate their electrical characteristics
Some are indicated with XYZ JKM VOLTS V where XYZ represents the capacitance (calculated
as XY x 10Z) the letters J K or M indicate the tolerance (plusmn5 plusmn10 and plusmn20 respectively) and
VOLTS V represents the working voltage
Example
A capacitor with the following text on its body
105 K 330 V has a capacitance of 10 x 105 pF = 1microF (plusmn10) with a working voltage of 330 V
A capacitor with the following text
473 M 100 V has a capacitance of 47 x 103 pF = 47 nF (plusmn20) with a working voltage of 100 V
A number code is often used on small capacitors where printing is difficult
The 1st number is the 1st digit
The 2nd number is the 2nd digit
The 3rd number is the number of zeros to give the capacitance in pF
Ignore any letters - they just indicate tolerance and voltage rating
For example 102 means 1000pF = 1nF (not 102pF)
For example 472J means 4700pF = 47nF (J means 5 tolerance)
It can be difficult to find the values of these small capacitors because there are many types of them
and several different labeling systems
Many small value capacitors have their value printed but without a multiplier so
you need to use experience to work out what the multiplier should be
For example 01 means 01microF = 100nF
Sometimes the multiplier is used in place of the decimal point
For example 4n7 means 47nF
BASIC ELECTRONICS ENGINEERING 8
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Color coding
Sr No Color Significant
digits
Multi-
pliers
Capacitance
tolerance
Characte
r-eristic
DC
working
voltage
Operating
temperature
1 Black 0 1 plusmn20 mdash mdash minus55 degC to +70
degC
2 Brown 1 10 plusmn1 B 100 mdash
3 Red 2 100 plusmn2 C mdash minus55 degC to
+85degC
4 Orange 3 1000 mdash D 300 mdash
5 Yellow 4 10000 mdash E mdash minus55 degC to
+125degC
6 Green 5 mdash plusmn5 F 500 mdash
7 Blue 6 mdash mdash mdash mdash minus55 degC to
+150 degC
8 Violet 7 mdash mdash mdash mdash mdash
9 Grey 8 mdash mdash mdash mdash mdash
10 White 9 mdash mdash mdash mdash mdash
11 Gold mdash mdash plusmn05 mdash 1000 mdash
12 Silver mdash mdash plusmn10 mdash mdash mdash
Or plusmn05 pF whichever is greater
A color code was used on polyester capacitors for many years The colors should be read like the
resistor code the top three color bands giving the value in pF Ignore the 4th band (tolerance) and
5th band (voltage rating)
BASIC ELECTRONICS ENGINEERING 9
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For example
Brown black orange means 10000pF = 10nF = 001microF
For example
Wide red yellow means 220nF = 022microF
(Note that there are no gaps between the color bands so 2 identical bands
actually appear as a wide band)Inductor
An inductor or a reactor is a passive electrical component that can store energy in a magnetic field
created by the electric current passing through it An inductors ability to store magnetic energy is
measured by its inductance in units of henries Typically an inductor is a conducting wire shaped
as a coil the loops helping to create a strong magnetic field inside the coil due to Faradays Law of
Induction Inductors are one of the basic electronic components used in electronics where current
and voltage change with time due to the ability of inductors to delay and reshape alternating
currents
Symbol of fixed inductor
Types of Inductor
1) Iron core Inductor This classification includes chokes and transformers both of which have
laminated iron cores A choke is a single winding and a transformer has two or more windings
Typical values of inductance for chokes range from 01 of a Henry to 50 henries Lamination
decreases eddy current losses
b) Air core Inductor It consists of number of turns of wire wound on a former made of cardboard
Since air is inside the former the inductor is called as air core inductor The only adjustment
available with air core inductors is by tapping all or part of a turn or by varying the spacing
between turns
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c) Ferrite core Inductor By inserting a ferrite or iron dust core in a coil it is possible to double its
inductance If the core is threaded its position within the coil can be varied to alter the inductance
This type of coil is used throughout the HF range and into the VHF for low-level signal circuits
Losses in the cores make them unsuitable for use in power circuits Values range from a few micro
henries to about a milli Henry
How to calculate the value of Inductor using color code
Some Radio Frequency chokes have their values indicated by a color code similar to that of
resistors
Applications
Filter chokes are used in smoothing pulsating current in rectifier Audio frequency chokes
are used to provide high impedance to audio frequencies Radio frequency chokes are used to block
the radio frequencies in communication systems
Switches
The term switch typically refers to electrical power or electronic telecommunication circuits In
applications where multiple switching options are required (eg a telephone service) mechanical
switches have long been replaced by electronic variants which can be intelligently controlled and
automated
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In the simplest case a switch has two pieces of metal called contacts that touch to make a circuit
and separate to break the circuit
There are different types of standard switches used in electronics
Type of Switch Circuit Symbol Example
1) ON-OFF Single Pole Single Throw =
SPST - A simple on-off switch Such
switches can be used to switch the power
supply to a circuit
SPST toggle switch
(ON)-OFF Push-to-make = SPST
Momentary - A push-to-make switch
returns to its normally open (off) position
when you release the button this is shown
by the brackets around ON This is the
standard doorbell switch
Push-to-make switch
ON-(OFF) Push-to-break = SPST
Momentary- A push-to-break switch
returns to its normally closed (on) position
when you release the button
Push-to-break switch
2) ON-ON Single Pole Double Throw =
SPDT - This switch can be on in both
positions switching on a separate device
in each case It is often called a
changeover switch A SPDT toggle
switch may be used as a simple on-off
switch by connecting to COM and one of
the A or B terminals shown in the
diagram
ON-OFF-ON SPDT Centre Off- A
special version of the standard SPDT
switch It has a third switching position in
the centre which is off Momentary (ON)-
OFF-(ON) versions are also available
where the switch returns to the central off
SPDT toggle switch
SPDT slide switch
(PCB mounting)
SPDT rocker switch
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position when released
3) Dual ON-OFF Double Pole Single
Throw = DPST- A pair of on-off switches
which operate together DPST switch is
often used to switch mains electricity
because it can isolate both the live and
neutral connections
DPST rocker switch
Dual ON-ON Double Pole Double
Throw = DPDT- A pair of on-on switches
which operate together (shown by the
dotted line in the circuit symbol) A DPDT
switch can be wired up as a reversing
switch for a motor as shown in the
diagram
ON-OFF-ON DPDT Centre Off -
A special version of the standard SPDT
switch It has a third switching position in
the centre which is off This can be very
useful for motor control because you have
forward off and reverse positions
Momentary (ON)-OFF-(ON) versions are
also available where the switch returns to
the central off position when released
DPDT slide switch
Wiring for Reversing
Switch
Special Switches
Type of Switch Example
1) Push-Push Switch (eg SPST = ON-OFF) - This looks like a
momentary action push switch but it is a standard on-off switch
push once to switch on push again to switch off This is called a
latching action
2) Micro switch (usually SPDT = ON-ON)-Micro switches are
designed to switch fully open or closed in response to small
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movements They are available with levers and rollers attached
3) Key switch - A key operated switch The example shown is
SPST
4) Tilt Switch (SPST) - Tilt switches contain a conductive liquid
and when tilted this bridges the contacts inside closing the
switch They can be used as a sensor to detect the position of an
object
5) Reed Switch (usually SPST) - The contacts of a reed switch
are closed by bringing a small magnet near the switch They are
used in security circuits for example to check that doors are
closed Standard reed switches are SPST (simple on-off) but
SPDT (changeover) versions are also available
6) DIP Switch (DIP = Dual In-line Parallel) - This is a set of
miniature SPST on-off switches the example shown has 8
switches The package is the same size as a standard DIL (Dual
In-Line) integrated circuit This type of switch is used to set up
circuits eg setting the code of a remote control
7) Multi-pole Switch - The picture shows a 6-pole double throw
switch also known as a 6-pole changeover switch It can be set
to have momentary or latching action Latching action means it
behaves as a push-push switch push once for the first position
push again for the second position etc
8) Multi-way (Rotary) Switch - Multi-way switches have 3 or
more conducting positions (Several poles contact sets) A
popular type has a rotary action and it is available with a range of
contact arrangements from 1-pole 12-way to 4-pole 3 way
Multi-way rotary switch
1-pole 4-way switch symbol
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9) Tactile Switch
These switches used in instruments keyboards
Connectors
An electrical connector is a conductive device for joining electrical circuits together The
connection may be temporary as for portable equipment or may require a tool for assembly and
removal or may be a permanent electrical joint between two wires or devices Connectors may join
two lengths of flexible wire or cable or may connect a wire or cable to an electrical terminal
There are hundreds of types of electrical connectors Out of that some of the connecters given
below
1) Battery clips and holders
The standard battery and battery holders such as the 6 times AA cell holder shown Battery holders are
also available with wires attached with pins for PCB mounting or as a complete box with lid
switch and wires
2) Terminal blocks and PCB terminals
Terminal blocks are usually supplied in 12-way lengths but they can be cut into smaller blocks with
a sharp knife large wire cutters or a junior hacksaw They are sometimes called chocolate blocks
because of the way they can be easily cut to size PCB mounting terminal blocks provide an easy
way of making semi-permanent connections to PCBs
PCB Terminal block
terminal
block
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3) Crocodile clips
The standard crocodile clip has no cover and a screw contact However miniature insulated
crocodile clips are more suitable for many purposes including test leads
Crocodile clips
4) 4mm plugs sockets and terminals
These are the standard single pole connectors used on meters and other electronic equipment They
are capable of passing high currents (typically 10A) and most designs are very robust
Plugs
Plugs may have a screw or solder terminal to hold the cable
Sockets
these are usually described as panel mounting because they are designed to be fitted to a case
Terminals
In addition to a socket these have provision for attaching a wire by threading it through a hole (or
wrapping it around the post) and tightening the top nut by hand
4mm terminal and solder tag
5) DC power plugs and sockets
These 2-pole plugs and sockets ensure that the polarity of a DC supply cannot be accidentally
reversed The standard sizes are 21 and 25mm plug diameter Standard plugs have a 10mm shaft
long plugs have a 14mm shaft
6) Jack plugs and sockets
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These are intended for audio signals so mono and stereo versions are available The sizes are
determined by the plug diameter frac14 (63mm) 35mm and 25mm The 25mm size is only
available for mono
frac14 (63mm) jack plug and socket 35mm jack plug and socket 35mm jack line socket
(for fitting to a cable)
35mm jack plug and socket connections
(the R connection is not present on mono plugs)
L = left channel signal R = right channel signal COM = common (0V screen) (Do not use jack
plugs for power supply connections because the contacts may be briefly shorted as the plug is
inserted Use DC power connectors for this)
7) Phono plugs and sockets
These are used for screened cables carrying audio and video signals Stereo connections are made
using a pair of phono plugs and sockets
8) Coax plugs and sockets
These are similar to the phono plugs and sockets described above but they are designed for use with
screened cables carrying much higher frequency signals such as TV aerial leads They provide
better screening because at high frequencies this is essential to reduce electrical noise
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Construction of a screened cable
9) BNC (Bayonet Neill-Concelman) plugs and sockets
These are designed for screened cables carrying high frequency signals where an undistorted and
noise free signal is essential for example oscilloscope leads BNC plugs are connected with a push
and twist action to disconnect you need to twist and pull
Plugs and sockets are rated by their impedance (50 or 75 ) which must be the same as the
cables impedance
11) D connectors
These are multi-pole connectors with provision for screw fittings to make semi-permanent
connections for example on computer equipment The D shape prevents incorrect connection
Standard D-connectors have 2 rows of contacts (top picture) 9 15 and 25-way versions are the
most popular
12) IDC communication connectors
These multi-pole insulation displacement connectors are used for computer and
telecommunications equipment They automatically cut through the insulation on wires when
installed and special tools are required to fit them They are available as 4 6 and 8-way versions
They are called BT (British Telecom) connectors
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13) USB Connector
The Universal Serial Bus is a serial bus standard to interface devices founded in 1996
Relays
A relay is an electrically operated switch Current flowing through the coil of the relay creates a
magnetic field which attracts a lever and changes the switch contacts The coil current can be on or
off so relays have two switch positions and they are double throw (changeover) switches Relays
allow one circuit to switch a second circuit which can be completely separate from the first For
example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit There is
no electrical connection inside the relay between the two circuits the link is magnetic and
mechanical
Following figure shows a working of relay with its coil and switch contacts You can see a
lever on the left being attracted by magnetism when the coil is switched on This lever moves the
switch contacts There is one set of contacts (SPDT) in the foreground and another behind them
making the relay DPDT
Circuit symbol for a relay Picture of a relay
The relays switch connections are usually labeled COM NC and NO
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COM = Common always connect to this it is the moving part of the switch
NC = Normally Closed COM is connected to this when the relay coil is off
NO = Normally Open COM is connected to this when the relay coil is on
Connect to COM and NO if you want the switched circuit to be on when the relay coil is
on
Connect to COM and NC if you want the switched circuit to be on when the relay coil is
off
Advantages of relays
Relays can switch AC and DC transistors can only switch DC
Relays can switch high voltages transistors cannot
Relays are a better choice for switching large currents (gt 5A)
Relays can switch many contacts at once
Disadvantages of relays
Relays are bulkier than transistors for switching small currents
Relays cannot switch rapidly (except reed relays) transistors can switch many times per
second
Relays use more power due to the current flowing through their coil
Relays require more current than many ICs can provide so a low power transistor may
be needed to switch the current for the relays coil
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductorsmdashthe transformers coils A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic field
through the secondary winding This varying magnetic field induces a varying electromotive force
(EMF) or voltage in the secondary winding This effect is called mutual induction
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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The resistive value of the resistor is controlled by increasing the desired thickness of the film and
then by laser cutting a spiral helix groove type pattern into this film It has much better temperature
stability low noise and is generally better for high frequency or radio frequency applications
3) Wire wound resistors-
Wire wound resistor is made by winding a thin metal alloy wire (Nichrome) or similar wire onto on
insulating ceramic former in the form of a spiral helix similar to the film resistors These types of
resistors are generally only available in very low ohmic high precision values (from 001 to
100Kohm) due to gauge of the wire and number of turns possible on the former making them ideal
for use in measuring circuits and Wheatstone bridge type applications
Types of Variable resistor
1) Potentiometer
A potentiometer (colloquially known as ―pot) is a three terminal resistor with sliding contact that
forms an adjustable voltage divider
Where A and B fixed terminals
W is the variable terminal
2) Rheostat
The most common way to vary the resistance in a circuit is to use a variable resistor or a rheostat
A rheostat is two terminal variable resistors
Symbol of Rheostat Actual picture of Rheostat
They are designed to handle much higher voltage and current Typically these are constructed as a
resistive wire wrapped to form a toroid coil with the moving over the upper surface of toroid
sliding from one turn of the wire to next
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3) Trimmer
A trimmer is a miniature adjustable electrical component It is called trimmer potentiometer or
trimpots
Actual pictures of the trimmers
How to calculate the value of fixed resistor using colour code
There are four color bands which are painted on resistors First band indicates first digit second
band indicate second digit and third band indicates the decimal multiplier
1st color band First digit
2nd
color band Second digit
3rd
color band Decimal multiplier
4th color band Tolerance
By using following table we can calculate the fixed resistors values
Capacitor
An electric circuit element which is used to store charge temporarily consisting in general of two
metallic plates (conductors) separated and insulated from each other by a dielectric Also called
condenser
Symbol of Capacitor
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When a voltage potential difference exists between the conductors an electric field is present in the
dielectric An ideal capacitor is characterized by a single constant value capacitance which is
measured in farads This is the ratio of the electric charge on each conductor to the potential
difference between them
Capacitors are widely used in electronic circuits to block the flow of direct current while allowing
alternating current to pass to filter out interference to smooth the output of power supplies and for
many other purposes They are used in resonant circuits in radio frequency equipment to select
particular frequencies from a signal with many frequencies
Types of Capacitors
A) Fixed Capacitors Types of fixed capacitors are
1) Electrolytic capacitors Aluminum Electrolytic Capacitors are polarized and can be used in DC
circuits Typical values range form 01uF to 68000uF Ideal for use in filtering and smoothing
applications in power supplies Also used for coupling and bypassing in audio circuits and as a
timing element in non-critical circuits They have a high reliability and low leakage
2) Paper capacitor In these paper is used as dielectric They are used for high voltage and high
current applications Sometimes on surface of paper vapors deposition of Zn or Al metal is made to
avoid separate winding of metal foil and paper
3) Mica Capacitor Natural mica has significant advantages It is inert It will not change
physically or chemically with age and hence good temperature ability
a) Small mica capacitor
b) Transmitting mica capacitors
4) Glass Capacitor It is stable durable and practically immune to temperature aging voltage
moisture vibrations Aluminum foil is used glass is drawn to 1mm thick flexible layers of foil are
interleaved and then leads are attached Then assembly is fused at high temperature
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5) Ceramic Capacitors These are manufactured in many shapes and sizes depending on
applications Dielectric material for this capacitor is high temperature sintered inorganic
compound
Types of Ceramic capacitors are
1] Disc ceramic capacitors
2] Tubular ceramic capacitors
3] Monolithic Ceramic Capacitors
4] Button Cart wheel door knob ceramic capacitors
6) Aluminum Electronic Capacitors These are electro chemical devices Two aluminum foils
separated by insulting papers are wound into cylinder The roll is impregnated with liquid
electrolyte stabilized
Other types of electrolytic capacitors are
1] Tantalum electrolytic capacitors
2] Tantalum foils electrolytic capacitors
3] Wet slug Tantalum capacitors
4] Solid electrolyte Tantalum capacitors
B) Variable Capacitors
Variable capacitors are mostly used in radio tuning circuits and they are sometimes called tuning
capacitors having very small capacitance values typically between 100pF and 500pF
(100pF = 00001microF)
Actual pictures of variable capacitor and trimmer with its symbols respectively
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How to calculate the value of Capacitor using number coding and colour coding
Most capacitors have numbers printed on their bodies to indicate their electrical characteristics
Some are indicated with XYZ JKM VOLTS V where XYZ represents the capacitance (calculated
as XY x 10Z) the letters J K or M indicate the tolerance (plusmn5 plusmn10 and plusmn20 respectively) and
VOLTS V represents the working voltage
Example
A capacitor with the following text on its body
105 K 330 V has a capacitance of 10 x 105 pF = 1microF (plusmn10) with a working voltage of 330 V
A capacitor with the following text
473 M 100 V has a capacitance of 47 x 103 pF = 47 nF (plusmn20) with a working voltage of 100 V
A number code is often used on small capacitors where printing is difficult
The 1st number is the 1st digit
The 2nd number is the 2nd digit
The 3rd number is the number of zeros to give the capacitance in pF
Ignore any letters - they just indicate tolerance and voltage rating
For example 102 means 1000pF = 1nF (not 102pF)
For example 472J means 4700pF = 47nF (J means 5 tolerance)
It can be difficult to find the values of these small capacitors because there are many types of them
and several different labeling systems
Many small value capacitors have their value printed but without a multiplier so
you need to use experience to work out what the multiplier should be
For example 01 means 01microF = 100nF
Sometimes the multiplier is used in place of the decimal point
For example 4n7 means 47nF
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Color coding
Sr No Color Significant
digits
Multi-
pliers
Capacitance
tolerance
Characte
r-eristic
DC
working
voltage
Operating
temperature
1 Black 0 1 plusmn20 mdash mdash minus55 degC to +70
degC
2 Brown 1 10 plusmn1 B 100 mdash
3 Red 2 100 plusmn2 C mdash minus55 degC to
+85degC
4 Orange 3 1000 mdash D 300 mdash
5 Yellow 4 10000 mdash E mdash minus55 degC to
+125degC
6 Green 5 mdash plusmn5 F 500 mdash
7 Blue 6 mdash mdash mdash mdash minus55 degC to
+150 degC
8 Violet 7 mdash mdash mdash mdash mdash
9 Grey 8 mdash mdash mdash mdash mdash
10 White 9 mdash mdash mdash mdash mdash
11 Gold mdash mdash plusmn05 mdash 1000 mdash
12 Silver mdash mdash plusmn10 mdash mdash mdash
Or plusmn05 pF whichever is greater
A color code was used on polyester capacitors for many years The colors should be read like the
resistor code the top three color bands giving the value in pF Ignore the 4th band (tolerance) and
5th band (voltage rating)
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For example
Brown black orange means 10000pF = 10nF = 001microF
For example
Wide red yellow means 220nF = 022microF
(Note that there are no gaps between the color bands so 2 identical bands
actually appear as a wide band)Inductor
An inductor or a reactor is a passive electrical component that can store energy in a magnetic field
created by the electric current passing through it An inductors ability to store magnetic energy is
measured by its inductance in units of henries Typically an inductor is a conducting wire shaped
as a coil the loops helping to create a strong magnetic field inside the coil due to Faradays Law of
Induction Inductors are one of the basic electronic components used in electronics where current
and voltage change with time due to the ability of inductors to delay and reshape alternating
currents
Symbol of fixed inductor
Types of Inductor
1) Iron core Inductor This classification includes chokes and transformers both of which have
laminated iron cores A choke is a single winding and a transformer has two or more windings
Typical values of inductance for chokes range from 01 of a Henry to 50 henries Lamination
decreases eddy current losses
b) Air core Inductor It consists of number of turns of wire wound on a former made of cardboard
Since air is inside the former the inductor is called as air core inductor The only adjustment
available with air core inductors is by tapping all or part of a turn or by varying the spacing
between turns
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c) Ferrite core Inductor By inserting a ferrite or iron dust core in a coil it is possible to double its
inductance If the core is threaded its position within the coil can be varied to alter the inductance
This type of coil is used throughout the HF range and into the VHF for low-level signal circuits
Losses in the cores make them unsuitable for use in power circuits Values range from a few micro
henries to about a milli Henry
How to calculate the value of Inductor using color code
Some Radio Frequency chokes have their values indicated by a color code similar to that of
resistors
Applications
Filter chokes are used in smoothing pulsating current in rectifier Audio frequency chokes
are used to provide high impedance to audio frequencies Radio frequency chokes are used to block
the radio frequencies in communication systems
Switches
The term switch typically refers to electrical power or electronic telecommunication circuits In
applications where multiple switching options are required (eg a telephone service) mechanical
switches have long been replaced by electronic variants which can be intelligently controlled and
automated
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In the simplest case a switch has two pieces of metal called contacts that touch to make a circuit
and separate to break the circuit
There are different types of standard switches used in electronics
Type of Switch Circuit Symbol Example
1) ON-OFF Single Pole Single Throw =
SPST - A simple on-off switch Such
switches can be used to switch the power
supply to a circuit
SPST toggle switch
(ON)-OFF Push-to-make = SPST
Momentary - A push-to-make switch
returns to its normally open (off) position
when you release the button this is shown
by the brackets around ON This is the
standard doorbell switch
Push-to-make switch
ON-(OFF) Push-to-break = SPST
Momentary- A push-to-break switch
returns to its normally closed (on) position
when you release the button
Push-to-break switch
2) ON-ON Single Pole Double Throw =
SPDT - This switch can be on in both
positions switching on a separate device
in each case It is often called a
changeover switch A SPDT toggle
switch may be used as a simple on-off
switch by connecting to COM and one of
the A or B terminals shown in the
diagram
ON-OFF-ON SPDT Centre Off- A
special version of the standard SPDT
switch It has a third switching position in
the centre which is off Momentary (ON)-
OFF-(ON) versions are also available
where the switch returns to the central off
SPDT toggle switch
SPDT slide switch
(PCB mounting)
SPDT rocker switch
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position when released
3) Dual ON-OFF Double Pole Single
Throw = DPST- A pair of on-off switches
which operate together DPST switch is
often used to switch mains electricity
because it can isolate both the live and
neutral connections
DPST rocker switch
Dual ON-ON Double Pole Double
Throw = DPDT- A pair of on-on switches
which operate together (shown by the
dotted line in the circuit symbol) A DPDT
switch can be wired up as a reversing
switch for a motor as shown in the
diagram
ON-OFF-ON DPDT Centre Off -
A special version of the standard SPDT
switch It has a third switching position in
the centre which is off This can be very
useful for motor control because you have
forward off and reverse positions
Momentary (ON)-OFF-(ON) versions are
also available where the switch returns to
the central off position when released
DPDT slide switch
Wiring for Reversing
Switch
Special Switches
Type of Switch Example
1) Push-Push Switch (eg SPST = ON-OFF) - This looks like a
momentary action push switch but it is a standard on-off switch
push once to switch on push again to switch off This is called a
latching action
2) Micro switch (usually SPDT = ON-ON)-Micro switches are
designed to switch fully open or closed in response to small
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movements They are available with levers and rollers attached
3) Key switch - A key operated switch The example shown is
SPST
4) Tilt Switch (SPST) - Tilt switches contain a conductive liquid
and when tilted this bridges the contacts inside closing the
switch They can be used as a sensor to detect the position of an
object
5) Reed Switch (usually SPST) - The contacts of a reed switch
are closed by bringing a small magnet near the switch They are
used in security circuits for example to check that doors are
closed Standard reed switches are SPST (simple on-off) but
SPDT (changeover) versions are also available
6) DIP Switch (DIP = Dual In-line Parallel) - This is a set of
miniature SPST on-off switches the example shown has 8
switches The package is the same size as a standard DIL (Dual
In-Line) integrated circuit This type of switch is used to set up
circuits eg setting the code of a remote control
7) Multi-pole Switch - The picture shows a 6-pole double throw
switch also known as a 6-pole changeover switch It can be set
to have momentary or latching action Latching action means it
behaves as a push-push switch push once for the first position
push again for the second position etc
8) Multi-way (Rotary) Switch - Multi-way switches have 3 or
more conducting positions (Several poles contact sets) A
popular type has a rotary action and it is available with a range of
contact arrangements from 1-pole 12-way to 4-pole 3 way
Multi-way rotary switch
1-pole 4-way switch symbol
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9) Tactile Switch
These switches used in instruments keyboards
Connectors
An electrical connector is a conductive device for joining electrical circuits together The
connection may be temporary as for portable equipment or may require a tool for assembly and
removal or may be a permanent electrical joint between two wires or devices Connectors may join
two lengths of flexible wire or cable or may connect a wire or cable to an electrical terminal
There are hundreds of types of electrical connectors Out of that some of the connecters given
below
1) Battery clips and holders
The standard battery and battery holders such as the 6 times AA cell holder shown Battery holders are
also available with wires attached with pins for PCB mounting or as a complete box with lid
switch and wires
2) Terminal blocks and PCB terminals
Terminal blocks are usually supplied in 12-way lengths but they can be cut into smaller blocks with
a sharp knife large wire cutters or a junior hacksaw They are sometimes called chocolate blocks
because of the way they can be easily cut to size PCB mounting terminal blocks provide an easy
way of making semi-permanent connections to PCBs
PCB Terminal block
terminal
block
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3) Crocodile clips
The standard crocodile clip has no cover and a screw contact However miniature insulated
crocodile clips are more suitable for many purposes including test leads
Crocodile clips
4) 4mm plugs sockets and terminals
These are the standard single pole connectors used on meters and other electronic equipment They
are capable of passing high currents (typically 10A) and most designs are very robust
Plugs
Plugs may have a screw or solder terminal to hold the cable
Sockets
these are usually described as panel mounting because they are designed to be fitted to a case
Terminals
In addition to a socket these have provision for attaching a wire by threading it through a hole (or
wrapping it around the post) and tightening the top nut by hand
4mm terminal and solder tag
5) DC power plugs and sockets
These 2-pole plugs and sockets ensure that the polarity of a DC supply cannot be accidentally
reversed The standard sizes are 21 and 25mm plug diameter Standard plugs have a 10mm shaft
long plugs have a 14mm shaft
6) Jack plugs and sockets
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These are intended for audio signals so mono and stereo versions are available The sizes are
determined by the plug diameter frac14 (63mm) 35mm and 25mm The 25mm size is only
available for mono
frac14 (63mm) jack plug and socket 35mm jack plug and socket 35mm jack line socket
(for fitting to a cable)
35mm jack plug and socket connections
(the R connection is not present on mono plugs)
L = left channel signal R = right channel signal COM = common (0V screen) (Do not use jack
plugs for power supply connections because the contacts may be briefly shorted as the plug is
inserted Use DC power connectors for this)
7) Phono plugs and sockets
These are used for screened cables carrying audio and video signals Stereo connections are made
using a pair of phono plugs and sockets
8) Coax plugs and sockets
These are similar to the phono plugs and sockets described above but they are designed for use with
screened cables carrying much higher frequency signals such as TV aerial leads They provide
better screening because at high frequencies this is essential to reduce electrical noise
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Construction of a screened cable
9) BNC (Bayonet Neill-Concelman) plugs and sockets
These are designed for screened cables carrying high frequency signals where an undistorted and
noise free signal is essential for example oscilloscope leads BNC plugs are connected with a push
and twist action to disconnect you need to twist and pull
Plugs and sockets are rated by their impedance (50 or 75 ) which must be the same as the
cables impedance
11) D connectors
These are multi-pole connectors with provision for screw fittings to make semi-permanent
connections for example on computer equipment The D shape prevents incorrect connection
Standard D-connectors have 2 rows of contacts (top picture) 9 15 and 25-way versions are the
most popular
12) IDC communication connectors
These multi-pole insulation displacement connectors are used for computer and
telecommunications equipment They automatically cut through the insulation on wires when
installed and special tools are required to fit them They are available as 4 6 and 8-way versions
They are called BT (British Telecom) connectors
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13) USB Connector
The Universal Serial Bus is a serial bus standard to interface devices founded in 1996
Relays
A relay is an electrically operated switch Current flowing through the coil of the relay creates a
magnetic field which attracts a lever and changes the switch contacts The coil current can be on or
off so relays have two switch positions and they are double throw (changeover) switches Relays
allow one circuit to switch a second circuit which can be completely separate from the first For
example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit There is
no electrical connection inside the relay between the two circuits the link is magnetic and
mechanical
Following figure shows a working of relay with its coil and switch contacts You can see a
lever on the left being attracted by magnetism when the coil is switched on This lever moves the
switch contacts There is one set of contacts (SPDT) in the foreground and another behind them
making the relay DPDT
Circuit symbol for a relay Picture of a relay
The relays switch connections are usually labeled COM NC and NO
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COM = Common always connect to this it is the moving part of the switch
NC = Normally Closed COM is connected to this when the relay coil is off
NO = Normally Open COM is connected to this when the relay coil is on
Connect to COM and NO if you want the switched circuit to be on when the relay coil is
on
Connect to COM and NC if you want the switched circuit to be on when the relay coil is
off
Advantages of relays
Relays can switch AC and DC transistors can only switch DC
Relays can switch high voltages transistors cannot
Relays are a better choice for switching large currents (gt 5A)
Relays can switch many contacts at once
Disadvantages of relays
Relays are bulkier than transistors for switching small currents
Relays cannot switch rapidly (except reed relays) transistors can switch many times per
second
Relays use more power due to the current flowing through their coil
Relays require more current than many ICs can provide so a low power transistor may
be needed to switch the current for the relays coil
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductorsmdashthe transformers coils A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic field
through the secondary winding This varying magnetic field induces a varying electromotive force
(EMF) or voltage in the secondary winding This effect is called mutual induction
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
BASIC ELECTRONICS ENGINEERING 24
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
BASIC ELECTRONICS ENGINEERING 28
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
BASIC ELECTRONICS ENGINEERING 60
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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3) Trimmer
A trimmer is a miniature adjustable electrical component It is called trimmer potentiometer or
trimpots
Actual pictures of the trimmers
How to calculate the value of fixed resistor using colour code
There are four color bands which are painted on resistors First band indicates first digit second
band indicate second digit and third band indicates the decimal multiplier
1st color band First digit
2nd
color band Second digit
3rd
color band Decimal multiplier
4th color band Tolerance
By using following table we can calculate the fixed resistors values
Capacitor
An electric circuit element which is used to store charge temporarily consisting in general of two
metallic plates (conductors) separated and insulated from each other by a dielectric Also called
condenser
Symbol of Capacitor
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When a voltage potential difference exists between the conductors an electric field is present in the
dielectric An ideal capacitor is characterized by a single constant value capacitance which is
measured in farads This is the ratio of the electric charge on each conductor to the potential
difference between them
Capacitors are widely used in electronic circuits to block the flow of direct current while allowing
alternating current to pass to filter out interference to smooth the output of power supplies and for
many other purposes They are used in resonant circuits in radio frequency equipment to select
particular frequencies from a signal with many frequencies
Types of Capacitors
A) Fixed Capacitors Types of fixed capacitors are
1) Electrolytic capacitors Aluminum Electrolytic Capacitors are polarized and can be used in DC
circuits Typical values range form 01uF to 68000uF Ideal for use in filtering and smoothing
applications in power supplies Also used for coupling and bypassing in audio circuits and as a
timing element in non-critical circuits They have a high reliability and low leakage
2) Paper capacitor In these paper is used as dielectric They are used for high voltage and high
current applications Sometimes on surface of paper vapors deposition of Zn or Al metal is made to
avoid separate winding of metal foil and paper
3) Mica Capacitor Natural mica has significant advantages It is inert It will not change
physically or chemically with age and hence good temperature ability
a) Small mica capacitor
b) Transmitting mica capacitors
4) Glass Capacitor It is stable durable and practically immune to temperature aging voltage
moisture vibrations Aluminum foil is used glass is drawn to 1mm thick flexible layers of foil are
interleaved and then leads are attached Then assembly is fused at high temperature
BASIC ELECTRONICS ENGINEERING 6
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5) Ceramic Capacitors These are manufactured in many shapes and sizes depending on
applications Dielectric material for this capacitor is high temperature sintered inorganic
compound
Types of Ceramic capacitors are
1] Disc ceramic capacitors
2] Tubular ceramic capacitors
3] Monolithic Ceramic Capacitors
4] Button Cart wheel door knob ceramic capacitors
6) Aluminum Electronic Capacitors These are electro chemical devices Two aluminum foils
separated by insulting papers are wound into cylinder The roll is impregnated with liquid
electrolyte stabilized
Other types of electrolytic capacitors are
1] Tantalum electrolytic capacitors
2] Tantalum foils electrolytic capacitors
3] Wet slug Tantalum capacitors
4] Solid electrolyte Tantalum capacitors
B) Variable Capacitors
Variable capacitors are mostly used in radio tuning circuits and they are sometimes called tuning
capacitors having very small capacitance values typically between 100pF and 500pF
(100pF = 00001microF)
Actual pictures of variable capacitor and trimmer with its symbols respectively
BASIC ELECTRONICS ENGINEERING 7
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How to calculate the value of Capacitor using number coding and colour coding
Most capacitors have numbers printed on their bodies to indicate their electrical characteristics
Some are indicated with XYZ JKM VOLTS V where XYZ represents the capacitance (calculated
as XY x 10Z) the letters J K or M indicate the tolerance (plusmn5 plusmn10 and plusmn20 respectively) and
VOLTS V represents the working voltage
Example
A capacitor with the following text on its body
105 K 330 V has a capacitance of 10 x 105 pF = 1microF (plusmn10) with a working voltage of 330 V
A capacitor with the following text
473 M 100 V has a capacitance of 47 x 103 pF = 47 nF (plusmn20) with a working voltage of 100 V
A number code is often used on small capacitors where printing is difficult
The 1st number is the 1st digit
The 2nd number is the 2nd digit
The 3rd number is the number of zeros to give the capacitance in pF
Ignore any letters - they just indicate tolerance and voltage rating
For example 102 means 1000pF = 1nF (not 102pF)
For example 472J means 4700pF = 47nF (J means 5 tolerance)
It can be difficult to find the values of these small capacitors because there are many types of them
and several different labeling systems
Many small value capacitors have their value printed but without a multiplier so
you need to use experience to work out what the multiplier should be
For example 01 means 01microF = 100nF
Sometimes the multiplier is used in place of the decimal point
For example 4n7 means 47nF
BASIC ELECTRONICS ENGINEERING 8
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Color coding
Sr No Color Significant
digits
Multi-
pliers
Capacitance
tolerance
Characte
r-eristic
DC
working
voltage
Operating
temperature
1 Black 0 1 plusmn20 mdash mdash minus55 degC to +70
degC
2 Brown 1 10 plusmn1 B 100 mdash
3 Red 2 100 plusmn2 C mdash minus55 degC to
+85degC
4 Orange 3 1000 mdash D 300 mdash
5 Yellow 4 10000 mdash E mdash minus55 degC to
+125degC
6 Green 5 mdash plusmn5 F 500 mdash
7 Blue 6 mdash mdash mdash mdash minus55 degC to
+150 degC
8 Violet 7 mdash mdash mdash mdash mdash
9 Grey 8 mdash mdash mdash mdash mdash
10 White 9 mdash mdash mdash mdash mdash
11 Gold mdash mdash plusmn05 mdash 1000 mdash
12 Silver mdash mdash plusmn10 mdash mdash mdash
Or plusmn05 pF whichever is greater
A color code was used on polyester capacitors for many years The colors should be read like the
resistor code the top three color bands giving the value in pF Ignore the 4th band (tolerance) and
5th band (voltage rating)
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For example
Brown black orange means 10000pF = 10nF = 001microF
For example
Wide red yellow means 220nF = 022microF
(Note that there are no gaps between the color bands so 2 identical bands
actually appear as a wide band)Inductor
An inductor or a reactor is a passive electrical component that can store energy in a magnetic field
created by the electric current passing through it An inductors ability to store magnetic energy is
measured by its inductance in units of henries Typically an inductor is a conducting wire shaped
as a coil the loops helping to create a strong magnetic field inside the coil due to Faradays Law of
Induction Inductors are one of the basic electronic components used in electronics where current
and voltage change with time due to the ability of inductors to delay and reshape alternating
currents
Symbol of fixed inductor
Types of Inductor
1) Iron core Inductor This classification includes chokes and transformers both of which have
laminated iron cores A choke is a single winding and a transformer has two or more windings
Typical values of inductance for chokes range from 01 of a Henry to 50 henries Lamination
decreases eddy current losses
b) Air core Inductor It consists of number of turns of wire wound on a former made of cardboard
Since air is inside the former the inductor is called as air core inductor The only adjustment
available with air core inductors is by tapping all or part of a turn or by varying the spacing
between turns
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c) Ferrite core Inductor By inserting a ferrite or iron dust core in a coil it is possible to double its
inductance If the core is threaded its position within the coil can be varied to alter the inductance
This type of coil is used throughout the HF range and into the VHF for low-level signal circuits
Losses in the cores make them unsuitable for use in power circuits Values range from a few micro
henries to about a milli Henry
How to calculate the value of Inductor using color code
Some Radio Frequency chokes have their values indicated by a color code similar to that of
resistors
Applications
Filter chokes are used in smoothing pulsating current in rectifier Audio frequency chokes
are used to provide high impedance to audio frequencies Radio frequency chokes are used to block
the radio frequencies in communication systems
Switches
The term switch typically refers to electrical power or electronic telecommunication circuits In
applications where multiple switching options are required (eg a telephone service) mechanical
switches have long been replaced by electronic variants which can be intelligently controlled and
automated
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In the simplest case a switch has two pieces of metal called contacts that touch to make a circuit
and separate to break the circuit
There are different types of standard switches used in electronics
Type of Switch Circuit Symbol Example
1) ON-OFF Single Pole Single Throw =
SPST - A simple on-off switch Such
switches can be used to switch the power
supply to a circuit
SPST toggle switch
(ON)-OFF Push-to-make = SPST
Momentary - A push-to-make switch
returns to its normally open (off) position
when you release the button this is shown
by the brackets around ON This is the
standard doorbell switch
Push-to-make switch
ON-(OFF) Push-to-break = SPST
Momentary- A push-to-break switch
returns to its normally closed (on) position
when you release the button
Push-to-break switch
2) ON-ON Single Pole Double Throw =
SPDT - This switch can be on in both
positions switching on a separate device
in each case It is often called a
changeover switch A SPDT toggle
switch may be used as a simple on-off
switch by connecting to COM and one of
the A or B terminals shown in the
diagram
ON-OFF-ON SPDT Centre Off- A
special version of the standard SPDT
switch It has a third switching position in
the centre which is off Momentary (ON)-
OFF-(ON) versions are also available
where the switch returns to the central off
SPDT toggle switch
SPDT slide switch
(PCB mounting)
SPDT rocker switch
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position when released
3) Dual ON-OFF Double Pole Single
Throw = DPST- A pair of on-off switches
which operate together DPST switch is
often used to switch mains electricity
because it can isolate both the live and
neutral connections
DPST rocker switch
Dual ON-ON Double Pole Double
Throw = DPDT- A pair of on-on switches
which operate together (shown by the
dotted line in the circuit symbol) A DPDT
switch can be wired up as a reversing
switch for a motor as shown in the
diagram
ON-OFF-ON DPDT Centre Off -
A special version of the standard SPDT
switch It has a third switching position in
the centre which is off This can be very
useful for motor control because you have
forward off and reverse positions
Momentary (ON)-OFF-(ON) versions are
also available where the switch returns to
the central off position when released
DPDT slide switch
Wiring for Reversing
Switch
Special Switches
Type of Switch Example
1) Push-Push Switch (eg SPST = ON-OFF) - This looks like a
momentary action push switch but it is a standard on-off switch
push once to switch on push again to switch off This is called a
latching action
2) Micro switch (usually SPDT = ON-ON)-Micro switches are
designed to switch fully open or closed in response to small
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movements They are available with levers and rollers attached
3) Key switch - A key operated switch The example shown is
SPST
4) Tilt Switch (SPST) - Tilt switches contain a conductive liquid
and when tilted this bridges the contacts inside closing the
switch They can be used as a sensor to detect the position of an
object
5) Reed Switch (usually SPST) - The contacts of a reed switch
are closed by bringing a small magnet near the switch They are
used in security circuits for example to check that doors are
closed Standard reed switches are SPST (simple on-off) but
SPDT (changeover) versions are also available
6) DIP Switch (DIP = Dual In-line Parallel) - This is a set of
miniature SPST on-off switches the example shown has 8
switches The package is the same size as a standard DIL (Dual
In-Line) integrated circuit This type of switch is used to set up
circuits eg setting the code of a remote control
7) Multi-pole Switch - The picture shows a 6-pole double throw
switch also known as a 6-pole changeover switch It can be set
to have momentary or latching action Latching action means it
behaves as a push-push switch push once for the first position
push again for the second position etc
8) Multi-way (Rotary) Switch - Multi-way switches have 3 or
more conducting positions (Several poles contact sets) A
popular type has a rotary action and it is available with a range of
contact arrangements from 1-pole 12-way to 4-pole 3 way
Multi-way rotary switch
1-pole 4-way switch symbol
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9) Tactile Switch
These switches used in instruments keyboards
Connectors
An electrical connector is a conductive device for joining electrical circuits together The
connection may be temporary as for portable equipment or may require a tool for assembly and
removal or may be a permanent electrical joint between two wires or devices Connectors may join
two lengths of flexible wire or cable or may connect a wire or cable to an electrical terminal
There are hundreds of types of electrical connectors Out of that some of the connecters given
below
1) Battery clips and holders
The standard battery and battery holders such as the 6 times AA cell holder shown Battery holders are
also available with wires attached with pins for PCB mounting or as a complete box with lid
switch and wires
2) Terminal blocks and PCB terminals
Terminal blocks are usually supplied in 12-way lengths but they can be cut into smaller blocks with
a sharp knife large wire cutters or a junior hacksaw They are sometimes called chocolate blocks
because of the way they can be easily cut to size PCB mounting terminal blocks provide an easy
way of making semi-permanent connections to PCBs
PCB Terminal block
terminal
block
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3) Crocodile clips
The standard crocodile clip has no cover and a screw contact However miniature insulated
crocodile clips are more suitable for many purposes including test leads
Crocodile clips
4) 4mm plugs sockets and terminals
These are the standard single pole connectors used on meters and other electronic equipment They
are capable of passing high currents (typically 10A) and most designs are very robust
Plugs
Plugs may have a screw or solder terminal to hold the cable
Sockets
these are usually described as panel mounting because they are designed to be fitted to a case
Terminals
In addition to a socket these have provision for attaching a wire by threading it through a hole (or
wrapping it around the post) and tightening the top nut by hand
4mm terminal and solder tag
5) DC power plugs and sockets
These 2-pole plugs and sockets ensure that the polarity of a DC supply cannot be accidentally
reversed The standard sizes are 21 and 25mm plug diameter Standard plugs have a 10mm shaft
long plugs have a 14mm shaft
6) Jack plugs and sockets
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These are intended for audio signals so mono and stereo versions are available The sizes are
determined by the plug diameter frac14 (63mm) 35mm and 25mm The 25mm size is only
available for mono
frac14 (63mm) jack plug and socket 35mm jack plug and socket 35mm jack line socket
(for fitting to a cable)
35mm jack plug and socket connections
(the R connection is not present on mono plugs)
L = left channel signal R = right channel signal COM = common (0V screen) (Do not use jack
plugs for power supply connections because the contacts may be briefly shorted as the plug is
inserted Use DC power connectors for this)
7) Phono plugs and sockets
These are used for screened cables carrying audio and video signals Stereo connections are made
using a pair of phono plugs and sockets
8) Coax plugs and sockets
These are similar to the phono plugs and sockets described above but they are designed for use with
screened cables carrying much higher frequency signals such as TV aerial leads They provide
better screening because at high frequencies this is essential to reduce electrical noise
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Construction of a screened cable
9) BNC (Bayonet Neill-Concelman) plugs and sockets
These are designed for screened cables carrying high frequency signals where an undistorted and
noise free signal is essential for example oscilloscope leads BNC plugs are connected with a push
and twist action to disconnect you need to twist and pull
Plugs and sockets are rated by their impedance (50 or 75 ) which must be the same as the
cables impedance
11) D connectors
These are multi-pole connectors with provision for screw fittings to make semi-permanent
connections for example on computer equipment The D shape prevents incorrect connection
Standard D-connectors have 2 rows of contacts (top picture) 9 15 and 25-way versions are the
most popular
12) IDC communication connectors
These multi-pole insulation displacement connectors are used for computer and
telecommunications equipment They automatically cut through the insulation on wires when
installed and special tools are required to fit them They are available as 4 6 and 8-way versions
They are called BT (British Telecom) connectors
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13) USB Connector
The Universal Serial Bus is a serial bus standard to interface devices founded in 1996
Relays
A relay is an electrically operated switch Current flowing through the coil of the relay creates a
magnetic field which attracts a lever and changes the switch contacts The coil current can be on or
off so relays have two switch positions and they are double throw (changeover) switches Relays
allow one circuit to switch a second circuit which can be completely separate from the first For
example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit There is
no electrical connection inside the relay between the two circuits the link is magnetic and
mechanical
Following figure shows a working of relay with its coil and switch contacts You can see a
lever on the left being attracted by magnetism when the coil is switched on This lever moves the
switch contacts There is one set of contacts (SPDT) in the foreground and another behind them
making the relay DPDT
Circuit symbol for a relay Picture of a relay
The relays switch connections are usually labeled COM NC and NO
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COM = Common always connect to this it is the moving part of the switch
NC = Normally Closed COM is connected to this when the relay coil is off
NO = Normally Open COM is connected to this when the relay coil is on
Connect to COM and NO if you want the switched circuit to be on when the relay coil is
on
Connect to COM and NC if you want the switched circuit to be on when the relay coil is
off
Advantages of relays
Relays can switch AC and DC transistors can only switch DC
Relays can switch high voltages transistors cannot
Relays are a better choice for switching large currents (gt 5A)
Relays can switch many contacts at once
Disadvantages of relays
Relays are bulkier than transistors for switching small currents
Relays cannot switch rapidly (except reed relays) transistors can switch many times per
second
Relays use more power due to the current flowing through their coil
Relays require more current than many ICs can provide so a low power transistor may
be needed to switch the current for the relays coil
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductorsmdashthe transformers coils A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic field
through the secondary winding This varying magnetic field induces a varying electromotive force
(EMF) or voltage in the secondary winding This effect is called mutual induction
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
BASIC ELECTRONICS ENGINEERING 39
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
BASIC ELECTRONICS ENGINEERING 40
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 42
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
BASIC ELECTRONICS ENGINEERING 45
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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When a voltage potential difference exists between the conductors an electric field is present in the
dielectric An ideal capacitor is characterized by a single constant value capacitance which is
measured in farads This is the ratio of the electric charge on each conductor to the potential
difference between them
Capacitors are widely used in electronic circuits to block the flow of direct current while allowing
alternating current to pass to filter out interference to smooth the output of power supplies and for
many other purposes They are used in resonant circuits in radio frequency equipment to select
particular frequencies from a signal with many frequencies
Types of Capacitors
A) Fixed Capacitors Types of fixed capacitors are
1) Electrolytic capacitors Aluminum Electrolytic Capacitors are polarized and can be used in DC
circuits Typical values range form 01uF to 68000uF Ideal for use in filtering and smoothing
applications in power supplies Also used for coupling and bypassing in audio circuits and as a
timing element in non-critical circuits They have a high reliability and low leakage
2) Paper capacitor In these paper is used as dielectric They are used for high voltage and high
current applications Sometimes on surface of paper vapors deposition of Zn or Al metal is made to
avoid separate winding of metal foil and paper
3) Mica Capacitor Natural mica has significant advantages It is inert It will not change
physically or chemically with age and hence good temperature ability
a) Small mica capacitor
b) Transmitting mica capacitors
4) Glass Capacitor It is stable durable and practically immune to temperature aging voltage
moisture vibrations Aluminum foil is used glass is drawn to 1mm thick flexible layers of foil are
interleaved and then leads are attached Then assembly is fused at high temperature
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5) Ceramic Capacitors These are manufactured in many shapes and sizes depending on
applications Dielectric material for this capacitor is high temperature sintered inorganic
compound
Types of Ceramic capacitors are
1] Disc ceramic capacitors
2] Tubular ceramic capacitors
3] Monolithic Ceramic Capacitors
4] Button Cart wheel door knob ceramic capacitors
6) Aluminum Electronic Capacitors These are electro chemical devices Two aluminum foils
separated by insulting papers are wound into cylinder The roll is impregnated with liquid
electrolyte stabilized
Other types of electrolytic capacitors are
1] Tantalum electrolytic capacitors
2] Tantalum foils electrolytic capacitors
3] Wet slug Tantalum capacitors
4] Solid electrolyte Tantalum capacitors
B) Variable Capacitors
Variable capacitors are mostly used in radio tuning circuits and they are sometimes called tuning
capacitors having very small capacitance values typically between 100pF and 500pF
(100pF = 00001microF)
Actual pictures of variable capacitor and trimmer with its symbols respectively
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How to calculate the value of Capacitor using number coding and colour coding
Most capacitors have numbers printed on their bodies to indicate their electrical characteristics
Some are indicated with XYZ JKM VOLTS V where XYZ represents the capacitance (calculated
as XY x 10Z) the letters J K or M indicate the tolerance (plusmn5 plusmn10 and plusmn20 respectively) and
VOLTS V represents the working voltage
Example
A capacitor with the following text on its body
105 K 330 V has a capacitance of 10 x 105 pF = 1microF (plusmn10) with a working voltage of 330 V
A capacitor with the following text
473 M 100 V has a capacitance of 47 x 103 pF = 47 nF (plusmn20) with a working voltage of 100 V
A number code is often used on small capacitors where printing is difficult
The 1st number is the 1st digit
The 2nd number is the 2nd digit
The 3rd number is the number of zeros to give the capacitance in pF
Ignore any letters - they just indicate tolerance and voltage rating
For example 102 means 1000pF = 1nF (not 102pF)
For example 472J means 4700pF = 47nF (J means 5 tolerance)
It can be difficult to find the values of these small capacitors because there are many types of them
and several different labeling systems
Many small value capacitors have their value printed but without a multiplier so
you need to use experience to work out what the multiplier should be
For example 01 means 01microF = 100nF
Sometimes the multiplier is used in place of the decimal point
For example 4n7 means 47nF
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Color coding
Sr No Color Significant
digits
Multi-
pliers
Capacitance
tolerance
Characte
r-eristic
DC
working
voltage
Operating
temperature
1 Black 0 1 plusmn20 mdash mdash minus55 degC to +70
degC
2 Brown 1 10 plusmn1 B 100 mdash
3 Red 2 100 plusmn2 C mdash minus55 degC to
+85degC
4 Orange 3 1000 mdash D 300 mdash
5 Yellow 4 10000 mdash E mdash minus55 degC to
+125degC
6 Green 5 mdash plusmn5 F 500 mdash
7 Blue 6 mdash mdash mdash mdash minus55 degC to
+150 degC
8 Violet 7 mdash mdash mdash mdash mdash
9 Grey 8 mdash mdash mdash mdash mdash
10 White 9 mdash mdash mdash mdash mdash
11 Gold mdash mdash plusmn05 mdash 1000 mdash
12 Silver mdash mdash plusmn10 mdash mdash mdash
Or plusmn05 pF whichever is greater
A color code was used on polyester capacitors for many years The colors should be read like the
resistor code the top three color bands giving the value in pF Ignore the 4th band (tolerance) and
5th band (voltage rating)
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For example
Brown black orange means 10000pF = 10nF = 001microF
For example
Wide red yellow means 220nF = 022microF
(Note that there are no gaps between the color bands so 2 identical bands
actually appear as a wide band)Inductor
An inductor or a reactor is a passive electrical component that can store energy in a magnetic field
created by the electric current passing through it An inductors ability to store magnetic energy is
measured by its inductance in units of henries Typically an inductor is a conducting wire shaped
as a coil the loops helping to create a strong magnetic field inside the coil due to Faradays Law of
Induction Inductors are one of the basic electronic components used in electronics where current
and voltage change with time due to the ability of inductors to delay and reshape alternating
currents
Symbol of fixed inductor
Types of Inductor
1) Iron core Inductor This classification includes chokes and transformers both of which have
laminated iron cores A choke is a single winding and a transformer has two or more windings
Typical values of inductance for chokes range from 01 of a Henry to 50 henries Lamination
decreases eddy current losses
b) Air core Inductor It consists of number of turns of wire wound on a former made of cardboard
Since air is inside the former the inductor is called as air core inductor The only adjustment
available with air core inductors is by tapping all or part of a turn or by varying the spacing
between turns
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c) Ferrite core Inductor By inserting a ferrite or iron dust core in a coil it is possible to double its
inductance If the core is threaded its position within the coil can be varied to alter the inductance
This type of coil is used throughout the HF range and into the VHF for low-level signal circuits
Losses in the cores make them unsuitable for use in power circuits Values range from a few micro
henries to about a milli Henry
How to calculate the value of Inductor using color code
Some Radio Frequency chokes have their values indicated by a color code similar to that of
resistors
Applications
Filter chokes are used in smoothing pulsating current in rectifier Audio frequency chokes
are used to provide high impedance to audio frequencies Radio frequency chokes are used to block
the radio frequencies in communication systems
Switches
The term switch typically refers to electrical power or electronic telecommunication circuits In
applications where multiple switching options are required (eg a telephone service) mechanical
switches have long been replaced by electronic variants which can be intelligently controlled and
automated
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In the simplest case a switch has two pieces of metal called contacts that touch to make a circuit
and separate to break the circuit
There are different types of standard switches used in electronics
Type of Switch Circuit Symbol Example
1) ON-OFF Single Pole Single Throw =
SPST - A simple on-off switch Such
switches can be used to switch the power
supply to a circuit
SPST toggle switch
(ON)-OFF Push-to-make = SPST
Momentary - A push-to-make switch
returns to its normally open (off) position
when you release the button this is shown
by the brackets around ON This is the
standard doorbell switch
Push-to-make switch
ON-(OFF) Push-to-break = SPST
Momentary- A push-to-break switch
returns to its normally closed (on) position
when you release the button
Push-to-break switch
2) ON-ON Single Pole Double Throw =
SPDT - This switch can be on in both
positions switching on a separate device
in each case It is often called a
changeover switch A SPDT toggle
switch may be used as a simple on-off
switch by connecting to COM and one of
the A or B terminals shown in the
diagram
ON-OFF-ON SPDT Centre Off- A
special version of the standard SPDT
switch It has a third switching position in
the centre which is off Momentary (ON)-
OFF-(ON) versions are also available
where the switch returns to the central off
SPDT toggle switch
SPDT slide switch
(PCB mounting)
SPDT rocker switch
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position when released
3) Dual ON-OFF Double Pole Single
Throw = DPST- A pair of on-off switches
which operate together DPST switch is
often used to switch mains electricity
because it can isolate both the live and
neutral connections
DPST rocker switch
Dual ON-ON Double Pole Double
Throw = DPDT- A pair of on-on switches
which operate together (shown by the
dotted line in the circuit symbol) A DPDT
switch can be wired up as a reversing
switch for a motor as shown in the
diagram
ON-OFF-ON DPDT Centre Off -
A special version of the standard SPDT
switch It has a third switching position in
the centre which is off This can be very
useful for motor control because you have
forward off and reverse positions
Momentary (ON)-OFF-(ON) versions are
also available where the switch returns to
the central off position when released
DPDT slide switch
Wiring for Reversing
Switch
Special Switches
Type of Switch Example
1) Push-Push Switch (eg SPST = ON-OFF) - This looks like a
momentary action push switch but it is a standard on-off switch
push once to switch on push again to switch off This is called a
latching action
2) Micro switch (usually SPDT = ON-ON)-Micro switches are
designed to switch fully open or closed in response to small
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movements They are available with levers and rollers attached
3) Key switch - A key operated switch The example shown is
SPST
4) Tilt Switch (SPST) - Tilt switches contain a conductive liquid
and when tilted this bridges the contacts inside closing the
switch They can be used as a sensor to detect the position of an
object
5) Reed Switch (usually SPST) - The contacts of a reed switch
are closed by bringing a small magnet near the switch They are
used in security circuits for example to check that doors are
closed Standard reed switches are SPST (simple on-off) but
SPDT (changeover) versions are also available
6) DIP Switch (DIP = Dual In-line Parallel) - This is a set of
miniature SPST on-off switches the example shown has 8
switches The package is the same size as a standard DIL (Dual
In-Line) integrated circuit This type of switch is used to set up
circuits eg setting the code of a remote control
7) Multi-pole Switch - The picture shows a 6-pole double throw
switch also known as a 6-pole changeover switch It can be set
to have momentary or latching action Latching action means it
behaves as a push-push switch push once for the first position
push again for the second position etc
8) Multi-way (Rotary) Switch - Multi-way switches have 3 or
more conducting positions (Several poles contact sets) A
popular type has a rotary action and it is available with a range of
contact arrangements from 1-pole 12-way to 4-pole 3 way
Multi-way rotary switch
1-pole 4-way switch symbol
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9) Tactile Switch
These switches used in instruments keyboards
Connectors
An electrical connector is a conductive device for joining electrical circuits together The
connection may be temporary as for portable equipment or may require a tool for assembly and
removal or may be a permanent electrical joint between two wires or devices Connectors may join
two lengths of flexible wire or cable or may connect a wire or cable to an electrical terminal
There are hundreds of types of electrical connectors Out of that some of the connecters given
below
1) Battery clips and holders
The standard battery and battery holders such as the 6 times AA cell holder shown Battery holders are
also available with wires attached with pins for PCB mounting or as a complete box with lid
switch and wires
2) Terminal blocks and PCB terminals
Terminal blocks are usually supplied in 12-way lengths but they can be cut into smaller blocks with
a sharp knife large wire cutters or a junior hacksaw They are sometimes called chocolate blocks
because of the way they can be easily cut to size PCB mounting terminal blocks provide an easy
way of making semi-permanent connections to PCBs
PCB Terminal block
terminal
block
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3) Crocodile clips
The standard crocodile clip has no cover and a screw contact However miniature insulated
crocodile clips are more suitable for many purposes including test leads
Crocodile clips
4) 4mm plugs sockets and terminals
These are the standard single pole connectors used on meters and other electronic equipment They
are capable of passing high currents (typically 10A) and most designs are very robust
Plugs
Plugs may have a screw or solder terminal to hold the cable
Sockets
these are usually described as panel mounting because they are designed to be fitted to a case
Terminals
In addition to a socket these have provision for attaching a wire by threading it through a hole (or
wrapping it around the post) and tightening the top nut by hand
4mm terminal and solder tag
5) DC power plugs and sockets
These 2-pole plugs and sockets ensure that the polarity of a DC supply cannot be accidentally
reversed The standard sizes are 21 and 25mm plug diameter Standard plugs have a 10mm shaft
long plugs have a 14mm shaft
6) Jack plugs and sockets
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These are intended for audio signals so mono and stereo versions are available The sizes are
determined by the plug diameter frac14 (63mm) 35mm and 25mm The 25mm size is only
available for mono
frac14 (63mm) jack plug and socket 35mm jack plug and socket 35mm jack line socket
(for fitting to a cable)
35mm jack plug and socket connections
(the R connection is not present on mono plugs)
L = left channel signal R = right channel signal COM = common (0V screen) (Do not use jack
plugs for power supply connections because the contacts may be briefly shorted as the plug is
inserted Use DC power connectors for this)
7) Phono plugs and sockets
These are used for screened cables carrying audio and video signals Stereo connections are made
using a pair of phono plugs and sockets
8) Coax plugs and sockets
These are similar to the phono plugs and sockets described above but they are designed for use with
screened cables carrying much higher frequency signals such as TV aerial leads They provide
better screening because at high frequencies this is essential to reduce electrical noise
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Construction of a screened cable
9) BNC (Bayonet Neill-Concelman) plugs and sockets
These are designed for screened cables carrying high frequency signals where an undistorted and
noise free signal is essential for example oscilloscope leads BNC plugs are connected with a push
and twist action to disconnect you need to twist and pull
Plugs and sockets are rated by their impedance (50 or 75 ) which must be the same as the
cables impedance
11) D connectors
These are multi-pole connectors with provision for screw fittings to make semi-permanent
connections for example on computer equipment The D shape prevents incorrect connection
Standard D-connectors have 2 rows of contacts (top picture) 9 15 and 25-way versions are the
most popular
12) IDC communication connectors
These multi-pole insulation displacement connectors are used for computer and
telecommunications equipment They automatically cut through the insulation on wires when
installed and special tools are required to fit them They are available as 4 6 and 8-way versions
They are called BT (British Telecom) connectors
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13) USB Connector
The Universal Serial Bus is a serial bus standard to interface devices founded in 1996
Relays
A relay is an electrically operated switch Current flowing through the coil of the relay creates a
magnetic field which attracts a lever and changes the switch contacts The coil current can be on or
off so relays have two switch positions and they are double throw (changeover) switches Relays
allow one circuit to switch a second circuit which can be completely separate from the first For
example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit There is
no electrical connection inside the relay between the two circuits the link is magnetic and
mechanical
Following figure shows a working of relay with its coil and switch contacts You can see a
lever on the left being attracted by magnetism when the coil is switched on This lever moves the
switch contacts There is one set of contacts (SPDT) in the foreground and another behind them
making the relay DPDT
Circuit symbol for a relay Picture of a relay
The relays switch connections are usually labeled COM NC and NO
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COM = Common always connect to this it is the moving part of the switch
NC = Normally Closed COM is connected to this when the relay coil is off
NO = Normally Open COM is connected to this when the relay coil is on
Connect to COM and NO if you want the switched circuit to be on when the relay coil is
on
Connect to COM and NC if you want the switched circuit to be on when the relay coil is
off
Advantages of relays
Relays can switch AC and DC transistors can only switch DC
Relays can switch high voltages transistors cannot
Relays are a better choice for switching large currents (gt 5A)
Relays can switch many contacts at once
Disadvantages of relays
Relays are bulkier than transistors for switching small currents
Relays cannot switch rapidly (except reed relays) transistors can switch many times per
second
Relays use more power due to the current flowing through their coil
Relays require more current than many ICs can provide so a low power transistor may
be needed to switch the current for the relays coil
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductorsmdashthe transformers coils A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic field
through the secondary winding This varying magnetic field induces a varying electromotive force
(EMF) or voltage in the secondary winding This effect is called mutual induction
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
BASIC ELECTRONICS ENGINEERING 59
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
BASIC ELECTRONICS ENGINEERING 60
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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5) Ceramic Capacitors These are manufactured in many shapes and sizes depending on
applications Dielectric material for this capacitor is high temperature sintered inorganic
compound
Types of Ceramic capacitors are
1] Disc ceramic capacitors
2] Tubular ceramic capacitors
3] Monolithic Ceramic Capacitors
4] Button Cart wheel door knob ceramic capacitors
6) Aluminum Electronic Capacitors These are electro chemical devices Two aluminum foils
separated by insulting papers are wound into cylinder The roll is impregnated with liquid
electrolyte stabilized
Other types of electrolytic capacitors are
1] Tantalum electrolytic capacitors
2] Tantalum foils electrolytic capacitors
3] Wet slug Tantalum capacitors
4] Solid electrolyte Tantalum capacitors
B) Variable Capacitors
Variable capacitors are mostly used in radio tuning circuits and they are sometimes called tuning
capacitors having very small capacitance values typically between 100pF and 500pF
(100pF = 00001microF)
Actual pictures of variable capacitor and trimmer with its symbols respectively
BASIC ELECTRONICS ENGINEERING 7
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How to calculate the value of Capacitor using number coding and colour coding
Most capacitors have numbers printed on their bodies to indicate their electrical characteristics
Some are indicated with XYZ JKM VOLTS V where XYZ represents the capacitance (calculated
as XY x 10Z) the letters J K or M indicate the tolerance (plusmn5 plusmn10 and plusmn20 respectively) and
VOLTS V represents the working voltage
Example
A capacitor with the following text on its body
105 K 330 V has a capacitance of 10 x 105 pF = 1microF (plusmn10) with a working voltage of 330 V
A capacitor with the following text
473 M 100 V has a capacitance of 47 x 103 pF = 47 nF (plusmn20) with a working voltage of 100 V
A number code is often used on small capacitors where printing is difficult
The 1st number is the 1st digit
The 2nd number is the 2nd digit
The 3rd number is the number of zeros to give the capacitance in pF
Ignore any letters - they just indicate tolerance and voltage rating
For example 102 means 1000pF = 1nF (not 102pF)
For example 472J means 4700pF = 47nF (J means 5 tolerance)
It can be difficult to find the values of these small capacitors because there are many types of them
and several different labeling systems
Many small value capacitors have their value printed but without a multiplier so
you need to use experience to work out what the multiplier should be
For example 01 means 01microF = 100nF
Sometimes the multiplier is used in place of the decimal point
For example 4n7 means 47nF
BASIC ELECTRONICS ENGINEERING 8
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Color coding
Sr No Color Significant
digits
Multi-
pliers
Capacitance
tolerance
Characte
r-eristic
DC
working
voltage
Operating
temperature
1 Black 0 1 plusmn20 mdash mdash minus55 degC to +70
degC
2 Brown 1 10 plusmn1 B 100 mdash
3 Red 2 100 plusmn2 C mdash minus55 degC to
+85degC
4 Orange 3 1000 mdash D 300 mdash
5 Yellow 4 10000 mdash E mdash minus55 degC to
+125degC
6 Green 5 mdash plusmn5 F 500 mdash
7 Blue 6 mdash mdash mdash mdash minus55 degC to
+150 degC
8 Violet 7 mdash mdash mdash mdash mdash
9 Grey 8 mdash mdash mdash mdash mdash
10 White 9 mdash mdash mdash mdash mdash
11 Gold mdash mdash plusmn05 mdash 1000 mdash
12 Silver mdash mdash plusmn10 mdash mdash mdash
Or plusmn05 pF whichever is greater
A color code was used on polyester capacitors for many years The colors should be read like the
resistor code the top three color bands giving the value in pF Ignore the 4th band (tolerance) and
5th band (voltage rating)
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For example
Brown black orange means 10000pF = 10nF = 001microF
For example
Wide red yellow means 220nF = 022microF
(Note that there are no gaps between the color bands so 2 identical bands
actually appear as a wide band)Inductor
An inductor or a reactor is a passive electrical component that can store energy in a magnetic field
created by the electric current passing through it An inductors ability to store magnetic energy is
measured by its inductance in units of henries Typically an inductor is a conducting wire shaped
as a coil the loops helping to create a strong magnetic field inside the coil due to Faradays Law of
Induction Inductors are one of the basic electronic components used in electronics where current
and voltage change with time due to the ability of inductors to delay and reshape alternating
currents
Symbol of fixed inductor
Types of Inductor
1) Iron core Inductor This classification includes chokes and transformers both of which have
laminated iron cores A choke is a single winding and a transformer has two or more windings
Typical values of inductance for chokes range from 01 of a Henry to 50 henries Lamination
decreases eddy current losses
b) Air core Inductor It consists of number of turns of wire wound on a former made of cardboard
Since air is inside the former the inductor is called as air core inductor The only adjustment
available with air core inductors is by tapping all or part of a turn or by varying the spacing
between turns
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c) Ferrite core Inductor By inserting a ferrite or iron dust core in a coil it is possible to double its
inductance If the core is threaded its position within the coil can be varied to alter the inductance
This type of coil is used throughout the HF range and into the VHF for low-level signal circuits
Losses in the cores make them unsuitable for use in power circuits Values range from a few micro
henries to about a milli Henry
How to calculate the value of Inductor using color code
Some Radio Frequency chokes have their values indicated by a color code similar to that of
resistors
Applications
Filter chokes are used in smoothing pulsating current in rectifier Audio frequency chokes
are used to provide high impedance to audio frequencies Radio frequency chokes are used to block
the radio frequencies in communication systems
Switches
The term switch typically refers to electrical power or electronic telecommunication circuits In
applications where multiple switching options are required (eg a telephone service) mechanical
switches have long been replaced by electronic variants which can be intelligently controlled and
automated
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In the simplest case a switch has two pieces of metal called contacts that touch to make a circuit
and separate to break the circuit
There are different types of standard switches used in electronics
Type of Switch Circuit Symbol Example
1) ON-OFF Single Pole Single Throw =
SPST - A simple on-off switch Such
switches can be used to switch the power
supply to a circuit
SPST toggle switch
(ON)-OFF Push-to-make = SPST
Momentary - A push-to-make switch
returns to its normally open (off) position
when you release the button this is shown
by the brackets around ON This is the
standard doorbell switch
Push-to-make switch
ON-(OFF) Push-to-break = SPST
Momentary- A push-to-break switch
returns to its normally closed (on) position
when you release the button
Push-to-break switch
2) ON-ON Single Pole Double Throw =
SPDT - This switch can be on in both
positions switching on a separate device
in each case It is often called a
changeover switch A SPDT toggle
switch may be used as a simple on-off
switch by connecting to COM and one of
the A or B terminals shown in the
diagram
ON-OFF-ON SPDT Centre Off- A
special version of the standard SPDT
switch It has a third switching position in
the centre which is off Momentary (ON)-
OFF-(ON) versions are also available
where the switch returns to the central off
SPDT toggle switch
SPDT slide switch
(PCB mounting)
SPDT rocker switch
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position when released
3) Dual ON-OFF Double Pole Single
Throw = DPST- A pair of on-off switches
which operate together DPST switch is
often used to switch mains electricity
because it can isolate both the live and
neutral connections
DPST rocker switch
Dual ON-ON Double Pole Double
Throw = DPDT- A pair of on-on switches
which operate together (shown by the
dotted line in the circuit symbol) A DPDT
switch can be wired up as a reversing
switch for a motor as shown in the
diagram
ON-OFF-ON DPDT Centre Off -
A special version of the standard SPDT
switch It has a third switching position in
the centre which is off This can be very
useful for motor control because you have
forward off and reverse positions
Momentary (ON)-OFF-(ON) versions are
also available where the switch returns to
the central off position when released
DPDT slide switch
Wiring for Reversing
Switch
Special Switches
Type of Switch Example
1) Push-Push Switch (eg SPST = ON-OFF) - This looks like a
momentary action push switch but it is a standard on-off switch
push once to switch on push again to switch off This is called a
latching action
2) Micro switch (usually SPDT = ON-ON)-Micro switches are
designed to switch fully open or closed in response to small
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movements They are available with levers and rollers attached
3) Key switch - A key operated switch The example shown is
SPST
4) Tilt Switch (SPST) - Tilt switches contain a conductive liquid
and when tilted this bridges the contacts inside closing the
switch They can be used as a sensor to detect the position of an
object
5) Reed Switch (usually SPST) - The contacts of a reed switch
are closed by bringing a small magnet near the switch They are
used in security circuits for example to check that doors are
closed Standard reed switches are SPST (simple on-off) but
SPDT (changeover) versions are also available
6) DIP Switch (DIP = Dual In-line Parallel) - This is a set of
miniature SPST on-off switches the example shown has 8
switches The package is the same size as a standard DIL (Dual
In-Line) integrated circuit This type of switch is used to set up
circuits eg setting the code of a remote control
7) Multi-pole Switch - The picture shows a 6-pole double throw
switch also known as a 6-pole changeover switch It can be set
to have momentary or latching action Latching action means it
behaves as a push-push switch push once for the first position
push again for the second position etc
8) Multi-way (Rotary) Switch - Multi-way switches have 3 or
more conducting positions (Several poles contact sets) A
popular type has a rotary action and it is available with a range of
contact arrangements from 1-pole 12-way to 4-pole 3 way
Multi-way rotary switch
1-pole 4-way switch symbol
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9) Tactile Switch
These switches used in instruments keyboards
Connectors
An electrical connector is a conductive device for joining electrical circuits together The
connection may be temporary as for portable equipment or may require a tool for assembly and
removal or may be a permanent electrical joint between two wires or devices Connectors may join
two lengths of flexible wire or cable or may connect a wire or cable to an electrical terminal
There are hundreds of types of electrical connectors Out of that some of the connecters given
below
1) Battery clips and holders
The standard battery and battery holders such as the 6 times AA cell holder shown Battery holders are
also available with wires attached with pins for PCB mounting or as a complete box with lid
switch and wires
2) Terminal blocks and PCB terminals
Terminal blocks are usually supplied in 12-way lengths but they can be cut into smaller blocks with
a sharp knife large wire cutters or a junior hacksaw They are sometimes called chocolate blocks
because of the way they can be easily cut to size PCB mounting terminal blocks provide an easy
way of making semi-permanent connections to PCBs
PCB Terminal block
terminal
block
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3) Crocodile clips
The standard crocodile clip has no cover and a screw contact However miniature insulated
crocodile clips are more suitable for many purposes including test leads
Crocodile clips
4) 4mm plugs sockets and terminals
These are the standard single pole connectors used on meters and other electronic equipment They
are capable of passing high currents (typically 10A) and most designs are very robust
Plugs
Plugs may have a screw or solder terminal to hold the cable
Sockets
these are usually described as panel mounting because they are designed to be fitted to a case
Terminals
In addition to a socket these have provision for attaching a wire by threading it through a hole (or
wrapping it around the post) and tightening the top nut by hand
4mm terminal and solder tag
5) DC power plugs and sockets
These 2-pole plugs and sockets ensure that the polarity of a DC supply cannot be accidentally
reversed The standard sizes are 21 and 25mm plug diameter Standard plugs have a 10mm shaft
long plugs have a 14mm shaft
6) Jack plugs and sockets
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These are intended for audio signals so mono and stereo versions are available The sizes are
determined by the plug diameter frac14 (63mm) 35mm and 25mm The 25mm size is only
available for mono
frac14 (63mm) jack plug and socket 35mm jack plug and socket 35mm jack line socket
(for fitting to a cable)
35mm jack plug and socket connections
(the R connection is not present on mono plugs)
L = left channel signal R = right channel signal COM = common (0V screen) (Do not use jack
plugs for power supply connections because the contacts may be briefly shorted as the plug is
inserted Use DC power connectors for this)
7) Phono plugs and sockets
These are used for screened cables carrying audio and video signals Stereo connections are made
using a pair of phono plugs and sockets
8) Coax plugs and sockets
These are similar to the phono plugs and sockets described above but they are designed for use with
screened cables carrying much higher frequency signals such as TV aerial leads They provide
better screening because at high frequencies this is essential to reduce electrical noise
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Construction of a screened cable
9) BNC (Bayonet Neill-Concelman) plugs and sockets
These are designed for screened cables carrying high frequency signals where an undistorted and
noise free signal is essential for example oscilloscope leads BNC plugs are connected with a push
and twist action to disconnect you need to twist and pull
Plugs and sockets are rated by their impedance (50 or 75 ) which must be the same as the
cables impedance
11) D connectors
These are multi-pole connectors with provision for screw fittings to make semi-permanent
connections for example on computer equipment The D shape prevents incorrect connection
Standard D-connectors have 2 rows of contacts (top picture) 9 15 and 25-way versions are the
most popular
12) IDC communication connectors
These multi-pole insulation displacement connectors are used for computer and
telecommunications equipment They automatically cut through the insulation on wires when
installed and special tools are required to fit them They are available as 4 6 and 8-way versions
They are called BT (British Telecom) connectors
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13) USB Connector
The Universal Serial Bus is a serial bus standard to interface devices founded in 1996
Relays
A relay is an electrically operated switch Current flowing through the coil of the relay creates a
magnetic field which attracts a lever and changes the switch contacts The coil current can be on or
off so relays have two switch positions and they are double throw (changeover) switches Relays
allow one circuit to switch a second circuit which can be completely separate from the first For
example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit There is
no electrical connection inside the relay between the two circuits the link is magnetic and
mechanical
Following figure shows a working of relay with its coil and switch contacts You can see a
lever on the left being attracted by magnetism when the coil is switched on This lever moves the
switch contacts There is one set of contacts (SPDT) in the foreground and another behind them
making the relay DPDT
Circuit symbol for a relay Picture of a relay
The relays switch connections are usually labeled COM NC and NO
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COM = Common always connect to this it is the moving part of the switch
NC = Normally Closed COM is connected to this when the relay coil is off
NO = Normally Open COM is connected to this when the relay coil is on
Connect to COM and NO if you want the switched circuit to be on when the relay coil is
on
Connect to COM and NC if you want the switched circuit to be on when the relay coil is
off
Advantages of relays
Relays can switch AC and DC transistors can only switch DC
Relays can switch high voltages transistors cannot
Relays are a better choice for switching large currents (gt 5A)
Relays can switch many contacts at once
Disadvantages of relays
Relays are bulkier than transistors for switching small currents
Relays cannot switch rapidly (except reed relays) transistors can switch many times per
second
Relays use more power due to the current flowing through their coil
Relays require more current than many ICs can provide so a low power transistor may
be needed to switch the current for the relays coil
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductorsmdashthe transformers coils A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic field
through the secondary winding This varying magnetic field induces a varying electromotive force
(EMF) or voltage in the secondary winding This effect is called mutual induction
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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How to calculate the value of Capacitor using number coding and colour coding
Most capacitors have numbers printed on their bodies to indicate their electrical characteristics
Some are indicated with XYZ JKM VOLTS V where XYZ represents the capacitance (calculated
as XY x 10Z) the letters J K or M indicate the tolerance (plusmn5 plusmn10 and plusmn20 respectively) and
VOLTS V represents the working voltage
Example
A capacitor with the following text on its body
105 K 330 V has a capacitance of 10 x 105 pF = 1microF (plusmn10) with a working voltage of 330 V
A capacitor with the following text
473 M 100 V has a capacitance of 47 x 103 pF = 47 nF (plusmn20) with a working voltage of 100 V
A number code is often used on small capacitors where printing is difficult
The 1st number is the 1st digit
The 2nd number is the 2nd digit
The 3rd number is the number of zeros to give the capacitance in pF
Ignore any letters - they just indicate tolerance and voltage rating
For example 102 means 1000pF = 1nF (not 102pF)
For example 472J means 4700pF = 47nF (J means 5 tolerance)
It can be difficult to find the values of these small capacitors because there are many types of them
and several different labeling systems
Many small value capacitors have their value printed but without a multiplier so
you need to use experience to work out what the multiplier should be
For example 01 means 01microF = 100nF
Sometimes the multiplier is used in place of the decimal point
For example 4n7 means 47nF
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Color coding
Sr No Color Significant
digits
Multi-
pliers
Capacitance
tolerance
Characte
r-eristic
DC
working
voltage
Operating
temperature
1 Black 0 1 plusmn20 mdash mdash minus55 degC to +70
degC
2 Brown 1 10 plusmn1 B 100 mdash
3 Red 2 100 plusmn2 C mdash minus55 degC to
+85degC
4 Orange 3 1000 mdash D 300 mdash
5 Yellow 4 10000 mdash E mdash minus55 degC to
+125degC
6 Green 5 mdash plusmn5 F 500 mdash
7 Blue 6 mdash mdash mdash mdash minus55 degC to
+150 degC
8 Violet 7 mdash mdash mdash mdash mdash
9 Grey 8 mdash mdash mdash mdash mdash
10 White 9 mdash mdash mdash mdash mdash
11 Gold mdash mdash plusmn05 mdash 1000 mdash
12 Silver mdash mdash plusmn10 mdash mdash mdash
Or plusmn05 pF whichever is greater
A color code was used on polyester capacitors for many years The colors should be read like the
resistor code the top three color bands giving the value in pF Ignore the 4th band (tolerance) and
5th band (voltage rating)
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For example
Brown black orange means 10000pF = 10nF = 001microF
For example
Wide red yellow means 220nF = 022microF
(Note that there are no gaps between the color bands so 2 identical bands
actually appear as a wide band)Inductor
An inductor or a reactor is a passive electrical component that can store energy in a magnetic field
created by the electric current passing through it An inductors ability to store magnetic energy is
measured by its inductance in units of henries Typically an inductor is a conducting wire shaped
as a coil the loops helping to create a strong magnetic field inside the coil due to Faradays Law of
Induction Inductors are one of the basic electronic components used in electronics where current
and voltage change with time due to the ability of inductors to delay and reshape alternating
currents
Symbol of fixed inductor
Types of Inductor
1) Iron core Inductor This classification includes chokes and transformers both of which have
laminated iron cores A choke is a single winding and a transformer has two or more windings
Typical values of inductance for chokes range from 01 of a Henry to 50 henries Lamination
decreases eddy current losses
b) Air core Inductor It consists of number of turns of wire wound on a former made of cardboard
Since air is inside the former the inductor is called as air core inductor The only adjustment
available with air core inductors is by tapping all or part of a turn or by varying the spacing
between turns
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c) Ferrite core Inductor By inserting a ferrite or iron dust core in a coil it is possible to double its
inductance If the core is threaded its position within the coil can be varied to alter the inductance
This type of coil is used throughout the HF range and into the VHF for low-level signal circuits
Losses in the cores make them unsuitable for use in power circuits Values range from a few micro
henries to about a milli Henry
How to calculate the value of Inductor using color code
Some Radio Frequency chokes have their values indicated by a color code similar to that of
resistors
Applications
Filter chokes are used in smoothing pulsating current in rectifier Audio frequency chokes
are used to provide high impedance to audio frequencies Radio frequency chokes are used to block
the radio frequencies in communication systems
Switches
The term switch typically refers to electrical power or electronic telecommunication circuits In
applications where multiple switching options are required (eg a telephone service) mechanical
switches have long been replaced by electronic variants which can be intelligently controlled and
automated
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In the simplest case a switch has two pieces of metal called contacts that touch to make a circuit
and separate to break the circuit
There are different types of standard switches used in electronics
Type of Switch Circuit Symbol Example
1) ON-OFF Single Pole Single Throw =
SPST - A simple on-off switch Such
switches can be used to switch the power
supply to a circuit
SPST toggle switch
(ON)-OFF Push-to-make = SPST
Momentary - A push-to-make switch
returns to its normally open (off) position
when you release the button this is shown
by the brackets around ON This is the
standard doorbell switch
Push-to-make switch
ON-(OFF) Push-to-break = SPST
Momentary- A push-to-break switch
returns to its normally closed (on) position
when you release the button
Push-to-break switch
2) ON-ON Single Pole Double Throw =
SPDT - This switch can be on in both
positions switching on a separate device
in each case It is often called a
changeover switch A SPDT toggle
switch may be used as a simple on-off
switch by connecting to COM and one of
the A or B terminals shown in the
diagram
ON-OFF-ON SPDT Centre Off- A
special version of the standard SPDT
switch It has a third switching position in
the centre which is off Momentary (ON)-
OFF-(ON) versions are also available
where the switch returns to the central off
SPDT toggle switch
SPDT slide switch
(PCB mounting)
SPDT rocker switch
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position when released
3) Dual ON-OFF Double Pole Single
Throw = DPST- A pair of on-off switches
which operate together DPST switch is
often used to switch mains electricity
because it can isolate both the live and
neutral connections
DPST rocker switch
Dual ON-ON Double Pole Double
Throw = DPDT- A pair of on-on switches
which operate together (shown by the
dotted line in the circuit symbol) A DPDT
switch can be wired up as a reversing
switch for a motor as shown in the
diagram
ON-OFF-ON DPDT Centre Off -
A special version of the standard SPDT
switch It has a third switching position in
the centre which is off This can be very
useful for motor control because you have
forward off and reverse positions
Momentary (ON)-OFF-(ON) versions are
also available where the switch returns to
the central off position when released
DPDT slide switch
Wiring for Reversing
Switch
Special Switches
Type of Switch Example
1) Push-Push Switch (eg SPST = ON-OFF) - This looks like a
momentary action push switch but it is a standard on-off switch
push once to switch on push again to switch off This is called a
latching action
2) Micro switch (usually SPDT = ON-ON)-Micro switches are
designed to switch fully open or closed in response to small
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movements They are available with levers and rollers attached
3) Key switch - A key operated switch The example shown is
SPST
4) Tilt Switch (SPST) - Tilt switches contain a conductive liquid
and when tilted this bridges the contacts inside closing the
switch They can be used as a sensor to detect the position of an
object
5) Reed Switch (usually SPST) - The contacts of a reed switch
are closed by bringing a small magnet near the switch They are
used in security circuits for example to check that doors are
closed Standard reed switches are SPST (simple on-off) but
SPDT (changeover) versions are also available
6) DIP Switch (DIP = Dual In-line Parallel) - This is a set of
miniature SPST on-off switches the example shown has 8
switches The package is the same size as a standard DIL (Dual
In-Line) integrated circuit This type of switch is used to set up
circuits eg setting the code of a remote control
7) Multi-pole Switch - The picture shows a 6-pole double throw
switch also known as a 6-pole changeover switch It can be set
to have momentary or latching action Latching action means it
behaves as a push-push switch push once for the first position
push again for the second position etc
8) Multi-way (Rotary) Switch - Multi-way switches have 3 or
more conducting positions (Several poles contact sets) A
popular type has a rotary action and it is available with a range of
contact arrangements from 1-pole 12-way to 4-pole 3 way
Multi-way rotary switch
1-pole 4-way switch symbol
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9) Tactile Switch
These switches used in instruments keyboards
Connectors
An electrical connector is a conductive device for joining electrical circuits together The
connection may be temporary as for portable equipment or may require a tool for assembly and
removal or may be a permanent electrical joint between two wires or devices Connectors may join
two lengths of flexible wire or cable or may connect a wire or cable to an electrical terminal
There are hundreds of types of electrical connectors Out of that some of the connecters given
below
1) Battery clips and holders
The standard battery and battery holders such as the 6 times AA cell holder shown Battery holders are
also available with wires attached with pins for PCB mounting or as a complete box with lid
switch and wires
2) Terminal blocks and PCB terminals
Terminal blocks are usually supplied in 12-way lengths but they can be cut into smaller blocks with
a sharp knife large wire cutters or a junior hacksaw They are sometimes called chocolate blocks
because of the way they can be easily cut to size PCB mounting terminal blocks provide an easy
way of making semi-permanent connections to PCBs
PCB Terminal block
terminal
block
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3) Crocodile clips
The standard crocodile clip has no cover and a screw contact However miniature insulated
crocodile clips are more suitable for many purposes including test leads
Crocodile clips
4) 4mm plugs sockets and terminals
These are the standard single pole connectors used on meters and other electronic equipment They
are capable of passing high currents (typically 10A) and most designs are very robust
Plugs
Plugs may have a screw or solder terminal to hold the cable
Sockets
these are usually described as panel mounting because they are designed to be fitted to a case
Terminals
In addition to a socket these have provision for attaching a wire by threading it through a hole (or
wrapping it around the post) and tightening the top nut by hand
4mm terminal and solder tag
5) DC power plugs and sockets
These 2-pole plugs and sockets ensure that the polarity of a DC supply cannot be accidentally
reversed The standard sizes are 21 and 25mm plug diameter Standard plugs have a 10mm shaft
long plugs have a 14mm shaft
6) Jack plugs and sockets
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These are intended for audio signals so mono and stereo versions are available The sizes are
determined by the plug diameter frac14 (63mm) 35mm and 25mm The 25mm size is only
available for mono
frac14 (63mm) jack plug and socket 35mm jack plug and socket 35mm jack line socket
(for fitting to a cable)
35mm jack plug and socket connections
(the R connection is not present on mono plugs)
L = left channel signal R = right channel signal COM = common (0V screen) (Do not use jack
plugs for power supply connections because the contacts may be briefly shorted as the plug is
inserted Use DC power connectors for this)
7) Phono plugs and sockets
These are used for screened cables carrying audio and video signals Stereo connections are made
using a pair of phono plugs and sockets
8) Coax plugs and sockets
These are similar to the phono plugs and sockets described above but they are designed for use with
screened cables carrying much higher frequency signals such as TV aerial leads They provide
better screening because at high frequencies this is essential to reduce electrical noise
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Construction of a screened cable
9) BNC (Bayonet Neill-Concelman) plugs and sockets
These are designed for screened cables carrying high frequency signals where an undistorted and
noise free signal is essential for example oscilloscope leads BNC plugs are connected with a push
and twist action to disconnect you need to twist and pull
Plugs and sockets are rated by their impedance (50 or 75 ) which must be the same as the
cables impedance
11) D connectors
These are multi-pole connectors with provision for screw fittings to make semi-permanent
connections for example on computer equipment The D shape prevents incorrect connection
Standard D-connectors have 2 rows of contacts (top picture) 9 15 and 25-way versions are the
most popular
12) IDC communication connectors
These multi-pole insulation displacement connectors are used for computer and
telecommunications equipment They automatically cut through the insulation on wires when
installed and special tools are required to fit them They are available as 4 6 and 8-way versions
They are called BT (British Telecom) connectors
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13) USB Connector
The Universal Serial Bus is a serial bus standard to interface devices founded in 1996
Relays
A relay is an electrically operated switch Current flowing through the coil of the relay creates a
magnetic field which attracts a lever and changes the switch contacts The coil current can be on or
off so relays have two switch positions and they are double throw (changeover) switches Relays
allow one circuit to switch a second circuit which can be completely separate from the first For
example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit There is
no electrical connection inside the relay between the two circuits the link is magnetic and
mechanical
Following figure shows a working of relay with its coil and switch contacts You can see a
lever on the left being attracted by magnetism when the coil is switched on This lever moves the
switch contacts There is one set of contacts (SPDT) in the foreground and another behind them
making the relay DPDT
Circuit symbol for a relay Picture of a relay
The relays switch connections are usually labeled COM NC and NO
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COM = Common always connect to this it is the moving part of the switch
NC = Normally Closed COM is connected to this when the relay coil is off
NO = Normally Open COM is connected to this when the relay coil is on
Connect to COM and NO if you want the switched circuit to be on when the relay coil is
on
Connect to COM and NC if you want the switched circuit to be on when the relay coil is
off
Advantages of relays
Relays can switch AC and DC transistors can only switch DC
Relays can switch high voltages transistors cannot
Relays are a better choice for switching large currents (gt 5A)
Relays can switch many contacts at once
Disadvantages of relays
Relays are bulkier than transistors for switching small currents
Relays cannot switch rapidly (except reed relays) transistors can switch many times per
second
Relays use more power due to the current flowing through their coil
Relays require more current than many ICs can provide so a low power transistor may
be needed to switch the current for the relays coil
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductorsmdashthe transformers coils A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic field
through the secondary winding This varying magnetic field induces a varying electromotive force
(EMF) or voltage in the secondary winding This effect is called mutual induction
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
BASIC ELECTRONICS ENGINEERING 28
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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Color coding
Sr No Color Significant
digits
Multi-
pliers
Capacitance
tolerance
Characte
r-eristic
DC
working
voltage
Operating
temperature
1 Black 0 1 plusmn20 mdash mdash minus55 degC to +70
degC
2 Brown 1 10 plusmn1 B 100 mdash
3 Red 2 100 plusmn2 C mdash minus55 degC to
+85degC
4 Orange 3 1000 mdash D 300 mdash
5 Yellow 4 10000 mdash E mdash minus55 degC to
+125degC
6 Green 5 mdash plusmn5 F 500 mdash
7 Blue 6 mdash mdash mdash mdash minus55 degC to
+150 degC
8 Violet 7 mdash mdash mdash mdash mdash
9 Grey 8 mdash mdash mdash mdash mdash
10 White 9 mdash mdash mdash mdash mdash
11 Gold mdash mdash plusmn05 mdash 1000 mdash
12 Silver mdash mdash plusmn10 mdash mdash mdash
Or plusmn05 pF whichever is greater
A color code was used on polyester capacitors for many years The colors should be read like the
resistor code the top three color bands giving the value in pF Ignore the 4th band (tolerance) and
5th band (voltage rating)
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For example
Brown black orange means 10000pF = 10nF = 001microF
For example
Wide red yellow means 220nF = 022microF
(Note that there are no gaps between the color bands so 2 identical bands
actually appear as a wide band)Inductor
An inductor or a reactor is a passive electrical component that can store energy in a magnetic field
created by the electric current passing through it An inductors ability to store magnetic energy is
measured by its inductance in units of henries Typically an inductor is a conducting wire shaped
as a coil the loops helping to create a strong magnetic field inside the coil due to Faradays Law of
Induction Inductors are one of the basic electronic components used in electronics where current
and voltage change with time due to the ability of inductors to delay and reshape alternating
currents
Symbol of fixed inductor
Types of Inductor
1) Iron core Inductor This classification includes chokes and transformers both of which have
laminated iron cores A choke is a single winding and a transformer has two or more windings
Typical values of inductance for chokes range from 01 of a Henry to 50 henries Lamination
decreases eddy current losses
b) Air core Inductor It consists of number of turns of wire wound on a former made of cardboard
Since air is inside the former the inductor is called as air core inductor The only adjustment
available with air core inductors is by tapping all or part of a turn or by varying the spacing
between turns
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c) Ferrite core Inductor By inserting a ferrite or iron dust core in a coil it is possible to double its
inductance If the core is threaded its position within the coil can be varied to alter the inductance
This type of coil is used throughout the HF range and into the VHF for low-level signal circuits
Losses in the cores make them unsuitable for use in power circuits Values range from a few micro
henries to about a milli Henry
How to calculate the value of Inductor using color code
Some Radio Frequency chokes have their values indicated by a color code similar to that of
resistors
Applications
Filter chokes are used in smoothing pulsating current in rectifier Audio frequency chokes
are used to provide high impedance to audio frequencies Radio frequency chokes are used to block
the radio frequencies in communication systems
Switches
The term switch typically refers to electrical power or electronic telecommunication circuits In
applications where multiple switching options are required (eg a telephone service) mechanical
switches have long been replaced by electronic variants which can be intelligently controlled and
automated
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In the simplest case a switch has two pieces of metal called contacts that touch to make a circuit
and separate to break the circuit
There are different types of standard switches used in electronics
Type of Switch Circuit Symbol Example
1) ON-OFF Single Pole Single Throw =
SPST - A simple on-off switch Such
switches can be used to switch the power
supply to a circuit
SPST toggle switch
(ON)-OFF Push-to-make = SPST
Momentary - A push-to-make switch
returns to its normally open (off) position
when you release the button this is shown
by the brackets around ON This is the
standard doorbell switch
Push-to-make switch
ON-(OFF) Push-to-break = SPST
Momentary- A push-to-break switch
returns to its normally closed (on) position
when you release the button
Push-to-break switch
2) ON-ON Single Pole Double Throw =
SPDT - This switch can be on in both
positions switching on a separate device
in each case It is often called a
changeover switch A SPDT toggle
switch may be used as a simple on-off
switch by connecting to COM and one of
the A or B terminals shown in the
diagram
ON-OFF-ON SPDT Centre Off- A
special version of the standard SPDT
switch It has a third switching position in
the centre which is off Momentary (ON)-
OFF-(ON) versions are also available
where the switch returns to the central off
SPDT toggle switch
SPDT slide switch
(PCB mounting)
SPDT rocker switch
BASIC ELECTRONICS ENGINEERING 12
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position when released
3) Dual ON-OFF Double Pole Single
Throw = DPST- A pair of on-off switches
which operate together DPST switch is
often used to switch mains electricity
because it can isolate both the live and
neutral connections
DPST rocker switch
Dual ON-ON Double Pole Double
Throw = DPDT- A pair of on-on switches
which operate together (shown by the
dotted line in the circuit symbol) A DPDT
switch can be wired up as a reversing
switch for a motor as shown in the
diagram
ON-OFF-ON DPDT Centre Off -
A special version of the standard SPDT
switch It has a third switching position in
the centre which is off This can be very
useful for motor control because you have
forward off and reverse positions
Momentary (ON)-OFF-(ON) versions are
also available where the switch returns to
the central off position when released
DPDT slide switch
Wiring for Reversing
Switch
Special Switches
Type of Switch Example
1) Push-Push Switch (eg SPST = ON-OFF) - This looks like a
momentary action push switch but it is a standard on-off switch
push once to switch on push again to switch off This is called a
latching action
2) Micro switch (usually SPDT = ON-ON)-Micro switches are
designed to switch fully open or closed in response to small
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movements They are available with levers and rollers attached
3) Key switch - A key operated switch The example shown is
SPST
4) Tilt Switch (SPST) - Tilt switches contain a conductive liquid
and when tilted this bridges the contacts inside closing the
switch They can be used as a sensor to detect the position of an
object
5) Reed Switch (usually SPST) - The contacts of a reed switch
are closed by bringing a small magnet near the switch They are
used in security circuits for example to check that doors are
closed Standard reed switches are SPST (simple on-off) but
SPDT (changeover) versions are also available
6) DIP Switch (DIP = Dual In-line Parallel) - This is a set of
miniature SPST on-off switches the example shown has 8
switches The package is the same size as a standard DIL (Dual
In-Line) integrated circuit This type of switch is used to set up
circuits eg setting the code of a remote control
7) Multi-pole Switch - The picture shows a 6-pole double throw
switch also known as a 6-pole changeover switch It can be set
to have momentary or latching action Latching action means it
behaves as a push-push switch push once for the first position
push again for the second position etc
8) Multi-way (Rotary) Switch - Multi-way switches have 3 or
more conducting positions (Several poles contact sets) A
popular type has a rotary action and it is available with a range of
contact arrangements from 1-pole 12-way to 4-pole 3 way
Multi-way rotary switch
1-pole 4-way switch symbol
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9) Tactile Switch
These switches used in instruments keyboards
Connectors
An electrical connector is a conductive device for joining electrical circuits together The
connection may be temporary as for portable equipment or may require a tool for assembly and
removal or may be a permanent electrical joint between two wires or devices Connectors may join
two lengths of flexible wire or cable or may connect a wire or cable to an electrical terminal
There are hundreds of types of electrical connectors Out of that some of the connecters given
below
1) Battery clips and holders
The standard battery and battery holders such as the 6 times AA cell holder shown Battery holders are
also available with wires attached with pins for PCB mounting or as a complete box with lid
switch and wires
2) Terminal blocks and PCB terminals
Terminal blocks are usually supplied in 12-way lengths but they can be cut into smaller blocks with
a sharp knife large wire cutters or a junior hacksaw They are sometimes called chocolate blocks
because of the way they can be easily cut to size PCB mounting terminal blocks provide an easy
way of making semi-permanent connections to PCBs
PCB Terminal block
terminal
block
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3) Crocodile clips
The standard crocodile clip has no cover and a screw contact However miniature insulated
crocodile clips are more suitable for many purposes including test leads
Crocodile clips
4) 4mm plugs sockets and terminals
These are the standard single pole connectors used on meters and other electronic equipment They
are capable of passing high currents (typically 10A) and most designs are very robust
Plugs
Plugs may have a screw or solder terminal to hold the cable
Sockets
these are usually described as panel mounting because they are designed to be fitted to a case
Terminals
In addition to a socket these have provision for attaching a wire by threading it through a hole (or
wrapping it around the post) and tightening the top nut by hand
4mm terminal and solder tag
5) DC power plugs and sockets
These 2-pole plugs and sockets ensure that the polarity of a DC supply cannot be accidentally
reversed The standard sizes are 21 and 25mm plug diameter Standard plugs have a 10mm shaft
long plugs have a 14mm shaft
6) Jack plugs and sockets
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These are intended for audio signals so mono and stereo versions are available The sizes are
determined by the plug diameter frac14 (63mm) 35mm and 25mm The 25mm size is only
available for mono
frac14 (63mm) jack plug and socket 35mm jack plug and socket 35mm jack line socket
(for fitting to a cable)
35mm jack plug and socket connections
(the R connection is not present on mono plugs)
L = left channel signal R = right channel signal COM = common (0V screen) (Do not use jack
plugs for power supply connections because the contacts may be briefly shorted as the plug is
inserted Use DC power connectors for this)
7) Phono plugs and sockets
These are used for screened cables carrying audio and video signals Stereo connections are made
using a pair of phono plugs and sockets
8) Coax plugs and sockets
These are similar to the phono plugs and sockets described above but they are designed for use with
screened cables carrying much higher frequency signals such as TV aerial leads They provide
better screening because at high frequencies this is essential to reduce electrical noise
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Construction of a screened cable
9) BNC (Bayonet Neill-Concelman) plugs and sockets
These are designed for screened cables carrying high frequency signals where an undistorted and
noise free signal is essential for example oscilloscope leads BNC plugs are connected with a push
and twist action to disconnect you need to twist and pull
Plugs and sockets are rated by their impedance (50 or 75 ) which must be the same as the
cables impedance
11) D connectors
These are multi-pole connectors with provision for screw fittings to make semi-permanent
connections for example on computer equipment The D shape prevents incorrect connection
Standard D-connectors have 2 rows of contacts (top picture) 9 15 and 25-way versions are the
most popular
12) IDC communication connectors
These multi-pole insulation displacement connectors are used for computer and
telecommunications equipment They automatically cut through the insulation on wires when
installed and special tools are required to fit them They are available as 4 6 and 8-way versions
They are called BT (British Telecom) connectors
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13) USB Connector
The Universal Serial Bus is a serial bus standard to interface devices founded in 1996
Relays
A relay is an electrically operated switch Current flowing through the coil of the relay creates a
magnetic field which attracts a lever and changes the switch contacts The coil current can be on or
off so relays have two switch positions and they are double throw (changeover) switches Relays
allow one circuit to switch a second circuit which can be completely separate from the first For
example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit There is
no electrical connection inside the relay between the two circuits the link is magnetic and
mechanical
Following figure shows a working of relay with its coil and switch contacts You can see a
lever on the left being attracted by magnetism when the coil is switched on This lever moves the
switch contacts There is one set of contacts (SPDT) in the foreground and another behind them
making the relay DPDT
Circuit symbol for a relay Picture of a relay
The relays switch connections are usually labeled COM NC and NO
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COM = Common always connect to this it is the moving part of the switch
NC = Normally Closed COM is connected to this when the relay coil is off
NO = Normally Open COM is connected to this when the relay coil is on
Connect to COM and NO if you want the switched circuit to be on when the relay coil is
on
Connect to COM and NC if you want the switched circuit to be on when the relay coil is
off
Advantages of relays
Relays can switch AC and DC transistors can only switch DC
Relays can switch high voltages transistors cannot
Relays are a better choice for switching large currents (gt 5A)
Relays can switch many contacts at once
Disadvantages of relays
Relays are bulkier than transistors for switching small currents
Relays cannot switch rapidly (except reed relays) transistors can switch many times per
second
Relays use more power due to the current flowing through their coil
Relays require more current than many ICs can provide so a low power transistor may
be needed to switch the current for the relays coil
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductorsmdashthe transformers coils A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic field
through the secondary winding This varying magnetic field induces a varying electromotive force
(EMF) or voltage in the secondary winding This effect is called mutual induction
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
BASIC ELECTRONICS ENGINEERING 50
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BASIC ELECTRONICS ENGINEERING 51
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
BASIC ELECTRONICS ENGINEERING 53
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
BASIC ELECTRONICS ENGINEERING 56
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
BASIC ELECTRONICS ENGINEERING 58
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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For example
Brown black orange means 10000pF = 10nF = 001microF
For example
Wide red yellow means 220nF = 022microF
(Note that there are no gaps between the color bands so 2 identical bands
actually appear as a wide band)Inductor
An inductor or a reactor is a passive electrical component that can store energy in a magnetic field
created by the electric current passing through it An inductors ability to store magnetic energy is
measured by its inductance in units of henries Typically an inductor is a conducting wire shaped
as a coil the loops helping to create a strong magnetic field inside the coil due to Faradays Law of
Induction Inductors are one of the basic electronic components used in electronics where current
and voltage change with time due to the ability of inductors to delay and reshape alternating
currents
Symbol of fixed inductor
Types of Inductor
1) Iron core Inductor This classification includes chokes and transformers both of which have
laminated iron cores A choke is a single winding and a transformer has two or more windings
Typical values of inductance for chokes range from 01 of a Henry to 50 henries Lamination
decreases eddy current losses
b) Air core Inductor It consists of number of turns of wire wound on a former made of cardboard
Since air is inside the former the inductor is called as air core inductor The only adjustment
available with air core inductors is by tapping all or part of a turn or by varying the spacing
between turns
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c) Ferrite core Inductor By inserting a ferrite or iron dust core in a coil it is possible to double its
inductance If the core is threaded its position within the coil can be varied to alter the inductance
This type of coil is used throughout the HF range and into the VHF for low-level signal circuits
Losses in the cores make them unsuitable for use in power circuits Values range from a few micro
henries to about a milli Henry
How to calculate the value of Inductor using color code
Some Radio Frequency chokes have their values indicated by a color code similar to that of
resistors
Applications
Filter chokes are used in smoothing pulsating current in rectifier Audio frequency chokes
are used to provide high impedance to audio frequencies Radio frequency chokes are used to block
the radio frequencies in communication systems
Switches
The term switch typically refers to electrical power or electronic telecommunication circuits In
applications where multiple switching options are required (eg a telephone service) mechanical
switches have long been replaced by electronic variants which can be intelligently controlled and
automated
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In the simplest case a switch has two pieces of metal called contacts that touch to make a circuit
and separate to break the circuit
There are different types of standard switches used in electronics
Type of Switch Circuit Symbol Example
1) ON-OFF Single Pole Single Throw =
SPST - A simple on-off switch Such
switches can be used to switch the power
supply to a circuit
SPST toggle switch
(ON)-OFF Push-to-make = SPST
Momentary - A push-to-make switch
returns to its normally open (off) position
when you release the button this is shown
by the brackets around ON This is the
standard doorbell switch
Push-to-make switch
ON-(OFF) Push-to-break = SPST
Momentary- A push-to-break switch
returns to its normally closed (on) position
when you release the button
Push-to-break switch
2) ON-ON Single Pole Double Throw =
SPDT - This switch can be on in both
positions switching on a separate device
in each case It is often called a
changeover switch A SPDT toggle
switch may be used as a simple on-off
switch by connecting to COM and one of
the A or B terminals shown in the
diagram
ON-OFF-ON SPDT Centre Off- A
special version of the standard SPDT
switch It has a third switching position in
the centre which is off Momentary (ON)-
OFF-(ON) versions are also available
where the switch returns to the central off
SPDT toggle switch
SPDT slide switch
(PCB mounting)
SPDT rocker switch
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position when released
3) Dual ON-OFF Double Pole Single
Throw = DPST- A pair of on-off switches
which operate together DPST switch is
often used to switch mains electricity
because it can isolate both the live and
neutral connections
DPST rocker switch
Dual ON-ON Double Pole Double
Throw = DPDT- A pair of on-on switches
which operate together (shown by the
dotted line in the circuit symbol) A DPDT
switch can be wired up as a reversing
switch for a motor as shown in the
diagram
ON-OFF-ON DPDT Centre Off -
A special version of the standard SPDT
switch It has a third switching position in
the centre which is off This can be very
useful for motor control because you have
forward off and reverse positions
Momentary (ON)-OFF-(ON) versions are
also available where the switch returns to
the central off position when released
DPDT slide switch
Wiring for Reversing
Switch
Special Switches
Type of Switch Example
1) Push-Push Switch (eg SPST = ON-OFF) - This looks like a
momentary action push switch but it is a standard on-off switch
push once to switch on push again to switch off This is called a
latching action
2) Micro switch (usually SPDT = ON-ON)-Micro switches are
designed to switch fully open or closed in response to small
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movements They are available with levers and rollers attached
3) Key switch - A key operated switch The example shown is
SPST
4) Tilt Switch (SPST) - Tilt switches contain a conductive liquid
and when tilted this bridges the contacts inside closing the
switch They can be used as a sensor to detect the position of an
object
5) Reed Switch (usually SPST) - The contacts of a reed switch
are closed by bringing a small magnet near the switch They are
used in security circuits for example to check that doors are
closed Standard reed switches are SPST (simple on-off) but
SPDT (changeover) versions are also available
6) DIP Switch (DIP = Dual In-line Parallel) - This is a set of
miniature SPST on-off switches the example shown has 8
switches The package is the same size as a standard DIL (Dual
In-Line) integrated circuit This type of switch is used to set up
circuits eg setting the code of a remote control
7) Multi-pole Switch - The picture shows a 6-pole double throw
switch also known as a 6-pole changeover switch It can be set
to have momentary or latching action Latching action means it
behaves as a push-push switch push once for the first position
push again for the second position etc
8) Multi-way (Rotary) Switch - Multi-way switches have 3 or
more conducting positions (Several poles contact sets) A
popular type has a rotary action and it is available with a range of
contact arrangements from 1-pole 12-way to 4-pole 3 way
Multi-way rotary switch
1-pole 4-way switch symbol
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9) Tactile Switch
These switches used in instruments keyboards
Connectors
An electrical connector is a conductive device for joining electrical circuits together The
connection may be temporary as for portable equipment or may require a tool for assembly and
removal or may be a permanent electrical joint between two wires or devices Connectors may join
two lengths of flexible wire or cable or may connect a wire or cable to an electrical terminal
There are hundreds of types of electrical connectors Out of that some of the connecters given
below
1) Battery clips and holders
The standard battery and battery holders such as the 6 times AA cell holder shown Battery holders are
also available with wires attached with pins for PCB mounting or as a complete box with lid
switch and wires
2) Terminal blocks and PCB terminals
Terminal blocks are usually supplied in 12-way lengths but they can be cut into smaller blocks with
a sharp knife large wire cutters or a junior hacksaw They are sometimes called chocolate blocks
because of the way they can be easily cut to size PCB mounting terminal blocks provide an easy
way of making semi-permanent connections to PCBs
PCB Terminal block
terminal
block
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3) Crocodile clips
The standard crocodile clip has no cover and a screw contact However miniature insulated
crocodile clips are more suitable for many purposes including test leads
Crocodile clips
4) 4mm plugs sockets and terminals
These are the standard single pole connectors used on meters and other electronic equipment They
are capable of passing high currents (typically 10A) and most designs are very robust
Plugs
Plugs may have a screw or solder terminal to hold the cable
Sockets
these are usually described as panel mounting because they are designed to be fitted to a case
Terminals
In addition to a socket these have provision for attaching a wire by threading it through a hole (or
wrapping it around the post) and tightening the top nut by hand
4mm terminal and solder tag
5) DC power plugs and sockets
These 2-pole plugs and sockets ensure that the polarity of a DC supply cannot be accidentally
reversed The standard sizes are 21 and 25mm plug diameter Standard plugs have a 10mm shaft
long plugs have a 14mm shaft
6) Jack plugs and sockets
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These are intended for audio signals so mono and stereo versions are available The sizes are
determined by the plug diameter frac14 (63mm) 35mm and 25mm The 25mm size is only
available for mono
frac14 (63mm) jack plug and socket 35mm jack plug and socket 35mm jack line socket
(for fitting to a cable)
35mm jack plug and socket connections
(the R connection is not present on mono plugs)
L = left channel signal R = right channel signal COM = common (0V screen) (Do not use jack
plugs for power supply connections because the contacts may be briefly shorted as the plug is
inserted Use DC power connectors for this)
7) Phono plugs and sockets
These are used for screened cables carrying audio and video signals Stereo connections are made
using a pair of phono plugs and sockets
8) Coax plugs and sockets
These are similar to the phono plugs and sockets described above but they are designed for use with
screened cables carrying much higher frequency signals such as TV aerial leads They provide
better screening because at high frequencies this is essential to reduce electrical noise
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Construction of a screened cable
9) BNC (Bayonet Neill-Concelman) plugs and sockets
These are designed for screened cables carrying high frequency signals where an undistorted and
noise free signal is essential for example oscilloscope leads BNC plugs are connected with a push
and twist action to disconnect you need to twist and pull
Plugs and sockets are rated by their impedance (50 or 75 ) which must be the same as the
cables impedance
11) D connectors
These are multi-pole connectors with provision for screw fittings to make semi-permanent
connections for example on computer equipment The D shape prevents incorrect connection
Standard D-connectors have 2 rows of contacts (top picture) 9 15 and 25-way versions are the
most popular
12) IDC communication connectors
These multi-pole insulation displacement connectors are used for computer and
telecommunications equipment They automatically cut through the insulation on wires when
installed and special tools are required to fit them They are available as 4 6 and 8-way versions
They are called BT (British Telecom) connectors
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13) USB Connector
The Universal Serial Bus is a serial bus standard to interface devices founded in 1996
Relays
A relay is an electrically operated switch Current flowing through the coil of the relay creates a
magnetic field which attracts a lever and changes the switch contacts The coil current can be on or
off so relays have two switch positions and they are double throw (changeover) switches Relays
allow one circuit to switch a second circuit which can be completely separate from the first For
example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit There is
no electrical connection inside the relay between the two circuits the link is magnetic and
mechanical
Following figure shows a working of relay with its coil and switch contacts You can see a
lever on the left being attracted by magnetism when the coil is switched on This lever moves the
switch contacts There is one set of contacts (SPDT) in the foreground and another behind them
making the relay DPDT
Circuit symbol for a relay Picture of a relay
The relays switch connections are usually labeled COM NC and NO
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COM = Common always connect to this it is the moving part of the switch
NC = Normally Closed COM is connected to this when the relay coil is off
NO = Normally Open COM is connected to this when the relay coil is on
Connect to COM and NO if you want the switched circuit to be on when the relay coil is
on
Connect to COM and NC if you want the switched circuit to be on when the relay coil is
off
Advantages of relays
Relays can switch AC and DC transistors can only switch DC
Relays can switch high voltages transistors cannot
Relays are a better choice for switching large currents (gt 5A)
Relays can switch many contacts at once
Disadvantages of relays
Relays are bulkier than transistors for switching small currents
Relays cannot switch rapidly (except reed relays) transistors can switch many times per
second
Relays use more power due to the current flowing through their coil
Relays require more current than many ICs can provide so a low power transistor may
be needed to switch the current for the relays coil
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductorsmdashthe transformers coils A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic field
through the secondary winding This varying magnetic field induces a varying electromotive force
(EMF) or voltage in the secondary winding This effect is called mutual induction
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
BASIC ELECTRONICS ENGINEERING 39
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
BASIC ELECTRONICS ENGINEERING 40
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 42
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
BASIC ELECTRONICS ENGINEERING 45
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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c) Ferrite core Inductor By inserting a ferrite or iron dust core in a coil it is possible to double its
inductance If the core is threaded its position within the coil can be varied to alter the inductance
This type of coil is used throughout the HF range and into the VHF for low-level signal circuits
Losses in the cores make them unsuitable for use in power circuits Values range from a few micro
henries to about a milli Henry
How to calculate the value of Inductor using color code
Some Radio Frequency chokes have their values indicated by a color code similar to that of
resistors
Applications
Filter chokes are used in smoothing pulsating current in rectifier Audio frequency chokes
are used to provide high impedance to audio frequencies Radio frequency chokes are used to block
the radio frequencies in communication systems
Switches
The term switch typically refers to electrical power or electronic telecommunication circuits In
applications where multiple switching options are required (eg a telephone service) mechanical
switches have long been replaced by electronic variants which can be intelligently controlled and
automated
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In the simplest case a switch has two pieces of metal called contacts that touch to make a circuit
and separate to break the circuit
There are different types of standard switches used in electronics
Type of Switch Circuit Symbol Example
1) ON-OFF Single Pole Single Throw =
SPST - A simple on-off switch Such
switches can be used to switch the power
supply to a circuit
SPST toggle switch
(ON)-OFF Push-to-make = SPST
Momentary - A push-to-make switch
returns to its normally open (off) position
when you release the button this is shown
by the brackets around ON This is the
standard doorbell switch
Push-to-make switch
ON-(OFF) Push-to-break = SPST
Momentary- A push-to-break switch
returns to its normally closed (on) position
when you release the button
Push-to-break switch
2) ON-ON Single Pole Double Throw =
SPDT - This switch can be on in both
positions switching on a separate device
in each case It is often called a
changeover switch A SPDT toggle
switch may be used as a simple on-off
switch by connecting to COM and one of
the A or B terminals shown in the
diagram
ON-OFF-ON SPDT Centre Off- A
special version of the standard SPDT
switch It has a third switching position in
the centre which is off Momentary (ON)-
OFF-(ON) versions are also available
where the switch returns to the central off
SPDT toggle switch
SPDT slide switch
(PCB mounting)
SPDT rocker switch
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position when released
3) Dual ON-OFF Double Pole Single
Throw = DPST- A pair of on-off switches
which operate together DPST switch is
often used to switch mains electricity
because it can isolate both the live and
neutral connections
DPST rocker switch
Dual ON-ON Double Pole Double
Throw = DPDT- A pair of on-on switches
which operate together (shown by the
dotted line in the circuit symbol) A DPDT
switch can be wired up as a reversing
switch for a motor as shown in the
diagram
ON-OFF-ON DPDT Centre Off -
A special version of the standard SPDT
switch It has a third switching position in
the centre which is off This can be very
useful for motor control because you have
forward off and reverse positions
Momentary (ON)-OFF-(ON) versions are
also available where the switch returns to
the central off position when released
DPDT slide switch
Wiring for Reversing
Switch
Special Switches
Type of Switch Example
1) Push-Push Switch (eg SPST = ON-OFF) - This looks like a
momentary action push switch but it is a standard on-off switch
push once to switch on push again to switch off This is called a
latching action
2) Micro switch (usually SPDT = ON-ON)-Micro switches are
designed to switch fully open or closed in response to small
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movements They are available with levers and rollers attached
3) Key switch - A key operated switch The example shown is
SPST
4) Tilt Switch (SPST) - Tilt switches contain a conductive liquid
and when tilted this bridges the contacts inside closing the
switch They can be used as a sensor to detect the position of an
object
5) Reed Switch (usually SPST) - The contacts of a reed switch
are closed by bringing a small magnet near the switch They are
used in security circuits for example to check that doors are
closed Standard reed switches are SPST (simple on-off) but
SPDT (changeover) versions are also available
6) DIP Switch (DIP = Dual In-line Parallel) - This is a set of
miniature SPST on-off switches the example shown has 8
switches The package is the same size as a standard DIL (Dual
In-Line) integrated circuit This type of switch is used to set up
circuits eg setting the code of a remote control
7) Multi-pole Switch - The picture shows a 6-pole double throw
switch also known as a 6-pole changeover switch It can be set
to have momentary or latching action Latching action means it
behaves as a push-push switch push once for the first position
push again for the second position etc
8) Multi-way (Rotary) Switch - Multi-way switches have 3 or
more conducting positions (Several poles contact sets) A
popular type has a rotary action and it is available with a range of
contact arrangements from 1-pole 12-way to 4-pole 3 way
Multi-way rotary switch
1-pole 4-way switch symbol
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9) Tactile Switch
These switches used in instruments keyboards
Connectors
An electrical connector is a conductive device for joining electrical circuits together The
connection may be temporary as for portable equipment or may require a tool for assembly and
removal or may be a permanent electrical joint between two wires or devices Connectors may join
two lengths of flexible wire or cable or may connect a wire or cable to an electrical terminal
There are hundreds of types of electrical connectors Out of that some of the connecters given
below
1) Battery clips and holders
The standard battery and battery holders such as the 6 times AA cell holder shown Battery holders are
also available with wires attached with pins for PCB mounting or as a complete box with lid
switch and wires
2) Terminal blocks and PCB terminals
Terminal blocks are usually supplied in 12-way lengths but they can be cut into smaller blocks with
a sharp knife large wire cutters or a junior hacksaw They are sometimes called chocolate blocks
because of the way they can be easily cut to size PCB mounting terminal blocks provide an easy
way of making semi-permanent connections to PCBs
PCB Terminal block
terminal
block
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3) Crocodile clips
The standard crocodile clip has no cover and a screw contact However miniature insulated
crocodile clips are more suitable for many purposes including test leads
Crocodile clips
4) 4mm plugs sockets and terminals
These are the standard single pole connectors used on meters and other electronic equipment They
are capable of passing high currents (typically 10A) and most designs are very robust
Plugs
Plugs may have a screw or solder terminal to hold the cable
Sockets
these are usually described as panel mounting because they are designed to be fitted to a case
Terminals
In addition to a socket these have provision for attaching a wire by threading it through a hole (or
wrapping it around the post) and tightening the top nut by hand
4mm terminal and solder tag
5) DC power plugs and sockets
These 2-pole plugs and sockets ensure that the polarity of a DC supply cannot be accidentally
reversed The standard sizes are 21 and 25mm plug diameter Standard plugs have a 10mm shaft
long plugs have a 14mm shaft
6) Jack plugs and sockets
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These are intended for audio signals so mono and stereo versions are available The sizes are
determined by the plug diameter frac14 (63mm) 35mm and 25mm The 25mm size is only
available for mono
frac14 (63mm) jack plug and socket 35mm jack plug and socket 35mm jack line socket
(for fitting to a cable)
35mm jack plug and socket connections
(the R connection is not present on mono plugs)
L = left channel signal R = right channel signal COM = common (0V screen) (Do not use jack
plugs for power supply connections because the contacts may be briefly shorted as the plug is
inserted Use DC power connectors for this)
7) Phono plugs and sockets
These are used for screened cables carrying audio and video signals Stereo connections are made
using a pair of phono plugs and sockets
8) Coax plugs and sockets
These are similar to the phono plugs and sockets described above but they are designed for use with
screened cables carrying much higher frequency signals such as TV aerial leads They provide
better screening because at high frequencies this is essential to reduce electrical noise
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Construction of a screened cable
9) BNC (Bayonet Neill-Concelman) plugs and sockets
These are designed for screened cables carrying high frequency signals where an undistorted and
noise free signal is essential for example oscilloscope leads BNC plugs are connected with a push
and twist action to disconnect you need to twist and pull
Plugs and sockets are rated by their impedance (50 or 75 ) which must be the same as the
cables impedance
11) D connectors
These are multi-pole connectors with provision for screw fittings to make semi-permanent
connections for example on computer equipment The D shape prevents incorrect connection
Standard D-connectors have 2 rows of contacts (top picture) 9 15 and 25-way versions are the
most popular
12) IDC communication connectors
These multi-pole insulation displacement connectors are used for computer and
telecommunications equipment They automatically cut through the insulation on wires when
installed and special tools are required to fit them They are available as 4 6 and 8-way versions
They are called BT (British Telecom) connectors
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13) USB Connector
The Universal Serial Bus is a serial bus standard to interface devices founded in 1996
Relays
A relay is an electrically operated switch Current flowing through the coil of the relay creates a
magnetic field which attracts a lever and changes the switch contacts The coil current can be on or
off so relays have two switch positions and they are double throw (changeover) switches Relays
allow one circuit to switch a second circuit which can be completely separate from the first For
example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit There is
no electrical connection inside the relay between the two circuits the link is magnetic and
mechanical
Following figure shows a working of relay with its coil and switch contacts You can see a
lever on the left being attracted by magnetism when the coil is switched on This lever moves the
switch contacts There is one set of contacts (SPDT) in the foreground and another behind them
making the relay DPDT
Circuit symbol for a relay Picture of a relay
The relays switch connections are usually labeled COM NC and NO
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COM = Common always connect to this it is the moving part of the switch
NC = Normally Closed COM is connected to this when the relay coil is off
NO = Normally Open COM is connected to this when the relay coil is on
Connect to COM and NO if you want the switched circuit to be on when the relay coil is
on
Connect to COM and NC if you want the switched circuit to be on when the relay coil is
off
Advantages of relays
Relays can switch AC and DC transistors can only switch DC
Relays can switch high voltages transistors cannot
Relays are a better choice for switching large currents (gt 5A)
Relays can switch many contacts at once
Disadvantages of relays
Relays are bulkier than transistors for switching small currents
Relays cannot switch rapidly (except reed relays) transistors can switch many times per
second
Relays use more power due to the current flowing through their coil
Relays require more current than many ICs can provide so a low power transistor may
be needed to switch the current for the relays coil
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductorsmdashthe transformers coils A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic field
through the secondary winding This varying magnetic field induces a varying electromotive force
(EMF) or voltage in the secondary winding This effect is called mutual induction
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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BASIC ELECTRONICS ENGINEERING 23
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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In the simplest case a switch has two pieces of metal called contacts that touch to make a circuit
and separate to break the circuit
There are different types of standard switches used in electronics
Type of Switch Circuit Symbol Example
1) ON-OFF Single Pole Single Throw =
SPST - A simple on-off switch Such
switches can be used to switch the power
supply to a circuit
SPST toggle switch
(ON)-OFF Push-to-make = SPST
Momentary - A push-to-make switch
returns to its normally open (off) position
when you release the button this is shown
by the brackets around ON This is the
standard doorbell switch
Push-to-make switch
ON-(OFF) Push-to-break = SPST
Momentary- A push-to-break switch
returns to its normally closed (on) position
when you release the button
Push-to-break switch
2) ON-ON Single Pole Double Throw =
SPDT - This switch can be on in both
positions switching on a separate device
in each case It is often called a
changeover switch A SPDT toggle
switch may be used as a simple on-off
switch by connecting to COM and one of
the A or B terminals shown in the
diagram
ON-OFF-ON SPDT Centre Off- A
special version of the standard SPDT
switch It has a third switching position in
the centre which is off Momentary (ON)-
OFF-(ON) versions are also available
where the switch returns to the central off
SPDT toggle switch
SPDT slide switch
(PCB mounting)
SPDT rocker switch
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position when released
3) Dual ON-OFF Double Pole Single
Throw = DPST- A pair of on-off switches
which operate together DPST switch is
often used to switch mains electricity
because it can isolate both the live and
neutral connections
DPST rocker switch
Dual ON-ON Double Pole Double
Throw = DPDT- A pair of on-on switches
which operate together (shown by the
dotted line in the circuit symbol) A DPDT
switch can be wired up as a reversing
switch for a motor as shown in the
diagram
ON-OFF-ON DPDT Centre Off -
A special version of the standard SPDT
switch It has a third switching position in
the centre which is off This can be very
useful for motor control because you have
forward off and reverse positions
Momentary (ON)-OFF-(ON) versions are
also available where the switch returns to
the central off position when released
DPDT slide switch
Wiring for Reversing
Switch
Special Switches
Type of Switch Example
1) Push-Push Switch (eg SPST = ON-OFF) - This looks like a
momentary action push switch but it is a standard on-off switch
push once to switch on push again to switch off This is called a
latching action
2) Micro switch (usually SPDT = ON-ON)-Micro switches are
designed to switch fully open or closed in response to small
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movements They are available with levers and rollers attached
3) Key switch - A key operated switch The example shown is
SPST
4) Tilt Switch (SPST) - Tilt switches contain a conductive liquid
and when tilted this bridges the contacts inside closing the
switch They can be used as a sensor to detect the position of an
object
5) Reed Switch (usually SPST) - The contacts of a reed switch
are closed by bringing a small magnet near the switch They are
used in security circuits for example to check that doors are
closed Standard reed switches are SPST (simple on-off) but
SPDT (changeover) versions are also available
6) DIP Switch (DIP = Dual In-line Parallel) - This is a set of
miniature SPST on-off switches the example shown has 8
switches The package is the same size as a standard DIL (Dual
In-Line) integrated circuit This type of switch is used to set up
circuits eg setting the code of a remote control
7) Multi-pole Switch - The picture shows a 6-pole double throw
switch also known as a 6-pole changeover switch It can be set
to have momentary or latching action Latching action means it
behaves as a push-push switch push once for the first position
push again for the second position etc
8) Multi-way (Rotary) Switch - Multi-way switches have 3 or
more conducting positions (Several poles contact sets) A
popular type has a rotary action and it is available with a range of
contact arrangements from 1-pole 12-way to 4-pole 3 way
Multi-way rotary switch
1-pole 4-way switch symbol
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9) Tactile Switch
These switches used in instruments keyboards
Connectors
An electrical connector is a conductive device for joining electrical circuits together The
connection may be temporary as for portable equipment or may require a tool for assembly and
removal or may be a permanent electrical joint between two wires or devices Connectors may join
two lengths of flexible wire or cable or may connect a wire or cable to an electrical terminal
There are hundreds of types of electrical connectors Out of that some of the connecters given
below
1) Battery clips and holders
The standard battery and battery holders such as the 6 times AA cell holder shown Battery holders are
also available with wires attached with pins for PCB mounting or as a complete box with lid
switch and wires
2) Terminal blocks and PCB terminals
Terminal blocks are usually supplied in 12-way lengths but they can be cut into smaller blocks with
a sharp knife large wire cutters or a junior hacksaw They are sometimes called chocolate blocks
because of the way they can be easily cut to size PCB mounting terminal blocks provide an easy
way of making semi-permanent connections to PCBs
PCB Terminal block
terminal
block
BASIC ELECTRONICS ENGINEERING 15
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3) Crocodile clips
The standard crocodile clip has no cover and a screw contact However miniature insulated
crocodile clips are more suitable for many purposes including test leads
Crocodile clips
4) 4mm plugs sockets and terminals
These are the standard single pole connectors used on meters and other electronic equipment They
are capable of passing high currents (typically 10A) and most designs are very robust
Plugs
Plugs may have a screw or solder terminal to hold the cable
Sockets
these are usually described as panel mounting because they are designed to be fitted to a case
Terminals
In addition to a socket these have provision for attaching a wire by threading it through a hole (or
wrapping it around the post) and tightening the top nut by hand
4mm terminal and solder tag
5) DC power plugs and sockets
These 2-pole plugs and sockets ensure that the polarity of a DC supply cannot be accidentally
reversed The standard sizes are 21 and 25mm plug diameter Standard plugs have a 10mm shaft
long plugs have a 14mm shaft
6) Jack plugs and sockets
BASIC ELECTRONICS ENGINEERING 16
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These are intended for audio signals so mono and stereo versions are available The sizes are
determined by the plug diameter frac14 (63mm) 35mm and 25mm The 25mm size is only
available for mono
frac14 (63mm) jack plug and socket 35mm jack plug and socket 35mm jack line socket
(for fitting to a cable)
35mm jack plug and socket connections
(the R connection is not present on mono plugs)
L = left channel signal R = right channel signal COM = common (0V screen) (Do not use jack
plugs for power supply connections because the contacts may be briefly shorted as the plug is
inserted Use DC power connectors for this)
7) Phono plugs and sockets
These are used for screened cables carrying audio and video signals Stereo connections are made
using a pair of phono plugs and sockets
8) Coax plugs and sockets
These are similar to the phono plugs and sockets described above but they are designed for use with
screened cables carrying much higher frequency signals such as TV aerial leads They provide
better screening because at high frequencies this is essential to reduce electrical noise
BASIC ELECTRONICS ENGINEERING 17
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Construction of a screened cable
9) BNC (Bayonet Neill-Concelman) plugs and sockets
These are designed for screened cables carrying high frequency signals where an undistorted and
noise free signal is essential for example oscilloscope leads BNC plugs are connected with a push
and twist action to disconnect you need to twist and pull
Plugs and sockets are rated by their impedance (50 or 75 ) which must be the same as the
cables impedance
11) D connectors
These are multi-pole connectors with provision for screw fittings to make semi-permanent
connections for example on computer equipment The D shape prevents incorrect connection
Standard D-connectors have 2 rows of contacts (top picture) 9 15 and 25-way versions are the
most popular
12) IDC communication connectors
These multi-pole insulation displacement connectors are used for computer and
telecommunications equipment They automatically cut through the insulation on wires when
installed and special tools are required to fit them They are available as 4 6 and 8-way versions
They are called BT (British Telecom) connectors
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13) USB Connector
The Universal Serial Bus is a serial bus standard to interface devices founded in 1996
Relays
A relay is an electrically operated switch Current flowing through the coil of the relay creates a
magnetic field which attracts a lever and changes the switch contacts The coil current can be on or
off so relays have two switch positions and they are double throw (changeover) switches Relays
allow one circuit to switch a second circuit which can be completely separate from the first For
example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit There is
no electrical connection inside the relay between the two circuits the link is magnetic and
mechanical
Following figure shows a working of relay with its coil and switch contacts You can see a
lever on the left being attracted by magnetism when the coil is switched on This lever moves the
switch contacts There is one set of contacts (SPDT) in the foreground and another behind them
making the relay DPDT
Circuit symbol for a relay Picture of a relay
The relays switch connections are usually labeled COM NC and NO
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COM = Common always connect to this it is the moving part of the switch
NC = Normally Closed COM is connected to this when the relay coil is off
NO = Normally Open COM is connected to this when the relay coil is on
Connect to COM and NO if you want the switched circuit to be on when the relay coil is
on
Connect to COM and NC if you want the switched circuit to be on when the relay coil is
off
Advantages of relays
Relays can switch AC and DC transistors can only switch DC
Relays can switch high voltages transistors cannot
Relays are a better choice for switching large currents (gt 5A)
Relays can switch many contacts at once
Disadvantages of relays
Relays are bulkier than transistors for switching small currents
Relays cannot switch rapidly (except reed relays) transistors can switch many times per
second
Relays use more power due to the current flowing through their coil
Relays require more current than many ICs can provide so a low power transistor may
be needed to switch the current for the relays coil
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductorsmdashthe transformers coils A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic field
through the secondary winding This varying magnetic field induces a varying electromotive force
(EMF) or voltage in the secondary winding This effect is called mutual induction
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 12
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position when released
3) Dual ON-OFF Double Pole Single
Throw = DPST- A pair of on-off switches
which operate together DPST switch is
often used to switch mains electricity
because it can isolate both the live and
neutral connections
DPST rocker switch
Dual ON-ON Double Pole Double
Throw = DPDT- A pair of on-on switches
which operate together (shown by the
dotted line in the circuit symbol) A DPDT
switch can be wired up as a reversing
switch for a motor as shown in the
diagram
ON-OFF-ON DPDT Centre Off -
A special version of the standard SPDT
switch It has a third switching position in
the centre which is off This can be very
useful for motor control because you have
forward off and reverse positions
Momentary (ON)-OFF-(ON) versions are
also available where the switch returns to
the central off position when released
DPDT slide switch
Wiring for Reversing
Switch
Special Switches
Type of Switch Example
1) Push-Push Switch (eg SPST = ON-OFF) - This looks like a
momentary action push switch but it is a standard on-off switch
push once to switch on push again to switch off This is called a
latching action
2) Micro switch (usually SPDT = ON-ON)-Micro switches are
designed to switch fully open or closed in response to small
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movements They are available with levers and rollers attached
3) Key switch - A key operated switch The example shown is
SPST
4) Tilt Switch (SPST) - Tilt switches contain a conductive liquid
and when tilted this bridges the contacts inside closing the
switch They can be used as a sensor to detect the position of an
object
5) Reed Switch (usually SPST) - The contacts of a reed switch
are closed by bringing a small magnet near the switch They are
used in security circuits for example to check that doors are
closed Standard reed switches are SPST (simple on-off) but
SPDT (changeover) versions are also available
6) DIP Switch (DIP = Dual In-line Parallel) - This is a set of
miniature SPST on-off switches the example shown has 8
switches The package is the same size as a standard DIL (Dual
In-Line) integrated circuit This type of switch is used to set up
circuits eg setting the code of a remote control
7) Multi-pole Switch - The picture shows a 6-pole double throw
switch also known as a 6-pole changeover switch It can be set
to have momentary or latching action Latching action means it
behaves as a push-push switch push once for the first position
push again for the second position etc
8) Multi-way (Rotary) Switch - Multi-way switches have 3 or
more conducting positions (Several poles contact sets) A
popular type has a rotary action and it is available with a range of
contact arrangements from 1-pole 12-way to 4-pole 3 way
Multi-way rotary switch
1-pole 4-way switch symbol
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9) Tactile Switch
These switches used in instruments keyboards
Connectors
An electrical connector is a conductive device for joining electrical circuits together The
connection may be temporary as for portable equipment or may require a tool for assembly and
removal or may be a permanent electrical joint between two wires or devices Connectors may join
two lengths of flexible wire or cable or may connect a wire or cable to an electrical terminal
There are hundreds of types of electrical connectors Out of that some of the connecters given
below
1) Battery clips and holders
The standard battery and battery holders such as the 6 times AA cell holder shown Battery holders are
also available with wires attached with pins for PCB mounting or as a complete box with lid
switch and wires
2) Terminal blocks and PCB terminals
Terminal blocks are usually supplied in 12-way lengths but they can be cut into smaller blocks with
a sharp knife large wire cutters or a junior hacksaw They are sometimes called chocolate blocks
because of the way they can be easily cut to size PCB mounting terminal blocks provide an easy
way of making semi-permanent connections to PCBs
PCB Terminal block
terminal
block
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3) Crocodile clips
The standard crocodile clip has no cover and a screw contact However miniature insulated
crocodile clips are more suitable for many purposes including test leads
Crocodile clips
4) 4mm plugs sockets and terminals
These are the standard single pole connectors used on meters and other electronic equipment They
are capable of passing high currents (typically 10A) and most designs are very robust
Plugs
Plugs may have a screw or solder terminal to hold the cable
Sockets
these are usually described as panel mounting because they are designed to be fitted to a case
Terminals
In addition to a socket these have provision for attaching a wire by threading it through a hole (or
wrapping it around the post) and tightening the top nut by hand
4mm terminal and solder tag
5) DC power plugs and sockets
These 2-pole plugs and sockets ensure that the polarity of a DC supply cannot be accidentally
reversed The standard sizes are 21 and 25mm plug diameter Standard plugs have a 10mm shaft
long plugs have a 14mm shaft
6) Jack plugs and sockets
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These are intended for audio signals so mono and stereo versions are available The sizes are
determined by the plug diameter frac14 (63mm) 35mm and 25mm The 25mm size is only
available for mono
frac14 (63mm) jack plug and socket 35mm jack plug and socket 35mm jack line socket
(for fitting to a cable)
35mm jack plug and socket connections
(the R connection is not present on mono plugs)
L = left channel signal R = right channel signal COM = common (0V screen) (Do not use jack
plugs for power supply connections because the contacts may be briefly shorted as the plug is
inserted Use DC power connectors for this)
7) Phono plugs and sockets
These are used for screened cables carrying audio and video signals Stereo connections are made
using a pair of phono plugs and sockets
8) Coax plugs and sockets
These are similar to the phono plugs and sockets described above but they are designed for use with
screened cables carrying much higher frequency signals such as TV aerial leads They provide
better screening because at high frequencies this is essential to reduce electrical noise
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Construction of a screened cable
9) BNC (Bayonet Neill-Concelman) plugs and sockets
These are designed for screened cables carrying high frequency signals where an undistorted and
noise free signal is essential for example oscilloscope leads BNC plugs are connected with a push
and twist action to disconnect you need to twist and pull
Plugs and sockets are rated by their impedance (50 or 75 ) which must be the same as the
cables impedance
11) D connectors
These are multi-pole connectors with provision for screw fittings to make semi-permanent
connections for example on computer equipment The D shape prevents incorrect connection
Standard D-connectors have 2 rows of contacts (top picture) 9 15 and 25-way versions are the
most popular
12) IDC communication connectors
These multi-pole insulation displacement connectors are used for computer and
telecommunications equipment They automatically cut through the insulation on wires when
installed and special tools are required to fit them They are available as 4 6 and 8-way versions
They are called BT (British Telecom) connectors
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13) USB Connector
The Universal Serial Bus is a serial bus standard to interface devices founded in 1996
Relays
A relay is an electrically operated switch Current flowing through the coil of the relay creates a
magnetic field which attracts a lever and changes the switch contacts The coil current can be on or
off so relays have two switch positions and they are double throw (changeover) switches Relays
allow one circuit to switch a second circuit which can be completely separate from the first For
example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit There is
no electrical connection inside the relay between the two circuits the link is magnetic and
mechanical
Following figure shows a working of relay with its coil and switch contacts You can see a
lever on the left being attracted by magnetism when the coil is switched on This lever moves the
switch contacts There is one set of contacts (SPDT) in the foreground and another behind them
making the relay DPDT
Circuit symbol for a relay Picture of a relay
The relays switch connections are usually labeled COM NC and NO
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COM = Common always connect to this it is the moving part of the switch
NC = Normally Closed COM is connected to this when the relay coil is off
NO = Normally Open COM is connected to this when the relay coil is on
Connect to COM and NO if you want the switched circuit to be on when the relay coil is
on
Connect to COM and NC if you want the switched circuit to be on when the relay coil is
off
Advantages of relays
Relays can switch AC and DC transistors can only switch DC
Relays can switch high voltages transistors cannot
Relays are a better choice for switching large currents (gt 5A)
Relays can switch many contacts at once
Disadvantages of relays
Relays are bulkier than transistors for switching small currents
Relays cannot switch rapidly (except reed relays) transistors can switch many times per
second
Relays use more power due to the current flowing through their coil
Relays require more current than many ICs can provide so a low power transistor may
be needed to switch the current for the relays coil
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductorsmdashthe transformers coils A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic field
through the secondary winding This varying magnetic field induces a varying electromotive force
(EMF) or voltage in the secondary winding This effect is called mutual induction
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
BASIC ELECTRONICS ENGINEERING 50
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BASIC ELECTRONICS ENGINEERING 51
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
BASIC ELECTRONICS ENGINEERING 53
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
BASIC ELECTRONICS ENGINEERING 54
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
BASIC ELECTRONICS ENGINEERING 56
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
BASIC ELECTRONICS ENGINEERING 58
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
BASIC ELECTRONICS ENGINEERING 64
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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movements They are available with levers and rollers attached
3) Key switch - A key operated switch The example shown is
SPST
4) Tilt Switch (SPST) - Tilt switches contain a conductive liquid
and when tilted this bridges the contacts inside closing the
switch They can be used as a sensor to detect the position of an
object
5) Reed Switch (usually SPST) - The contacts of a reed switch
are closed by bringing a small magnet near the switch They are
used in security circuits for example to check that doors are
closed Standard reed switches are SPST (simple on-off) but
SPDT (changeover) versions are also available
6) DIP Switch (DIP = Dual In-line Parallel) - This is a set of
miniature SPST on-off switches the example shown has 8
switches The package is the same size as a standard DIL (Dual
In-Line) integrated circuit This type of switch is used to set up
circuits eg setting the code of a remote control
7) Multi-pole Switch - The picture shows a 6-pole double throw
switch also known as a 6-pole changeover switch It can be set
to have momentary or latching action Latching action means it
behaves as a push-push switch push once for the first position
push again for the second position etc
8) Multi-way (Rotary) Switch - Multi-way switches have 3 or
more conducting positions (Several poles contact sets) A
popular type has a rotary action and it is available with a range of
contact arrangements from 1-pole 12-way to 4-pole 3 way
Multi-way rotary switch
1-pole 4-way switch symbol
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9) Tactile Switch
These switches used in instruments keyboards
Connectors
An electrical connector is a conductive device for joining electrical circuits together The
connection may be temporary as for portable equipment or may require a tool for assembly and
removal or may be a permanent electrical joint between two wires or devices Connectors may join
two lengths of flexible wire or cable or may connect a wire or cable to an electrical terminal
There are hundreds of types of electrical connectors Out of that some of the connecters given
below
1) Battery clips and holders
The standard battery and battery holders such as the 6 times AA cell holder shown Battery holders are
also available with wires attached with pins for PCB mounting or as a complete box with lid
switch and wires
2) Terminal blocks and PCB terminals
Terminal blocks are usually supplied in 12-way lengths but they can be cut into smaller blocks with
a sharp knife large wire cutters or a junior hacksaw They are sometimes called chocolate blocks
because of the way they can be easily cut to size PCB mounting terminal blocks provide an easy
way of making semi-permanent connections to PCBs
PCB Terminal block
terminal
block
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3) Crocodile clips
The standard crocodile clip has no cover and a screw contact However miniature insulated
crocodile clips are more suitable for many purposes including test leads
Crocodile clips
4) 4mm plugs sockets and terminals
These are the standard single pole connectors used on meters and other electronic equipment They
are capable of passing high currents (typically 10A) and most designs are very robust
Plugs
Plugs may have a screw or solder terminal to hold the cable
Sockets
these are usually described as panel mounting because they are designed to be fitted to a case
Terminals
In addition to a socket these have provision for attaching a wire by threading it through a hole (or
wrapping it around the post) and tightening the top nut by hand
4mm terminal and solder tag
5) DC power plugs and sockets
These 2-pole plugs and sockets ensure that the polarity of a DC supply cannot be accidentally
reversed The standard sizes are 21 and 25mm plug diameter Standard plugs have a 10mm shaft
long plugs have a 14mm shaft
6) Jack plugs and sockets
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These are intended for audio signals so mono and stereo versions are available The sizes are
determined by the plug diameter frac14 (63mm) 35mm and 25mm The 25mm size is only
available for mono
frac14 (63mm) jack plug and socket 35mm jack plug and socket 35mm jack line socket
(for fitting to a cable)
35mm jack plug and socket connections
(the R connection is not present on mono plugs)
L = left channel signal R = right channel signal COM = common (0V screen) (Do not use jack
plugs for power supply connections because the contacts may be briefly shorted as the plug is
inserted Use DC power connectors for this)
7) Phono plugs and sockets
These are used for screened cables carrying audio and video signals Stereo connections are made
using a pair of phono plugs and sockets
8) Coax plugs and sockets
These are similar to the phono plugs and sockets described above but they are designed for use with
screened cables carrying much higher frequency signals such as TV aerial leads They provide
better screening because at high frequencies this is essential to reduce electrical noise
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Construction of a screened cable
9) BNC (Bayonet Neill-Concelman) plugs and sockets
These are designed for screened cables carrying high frequency signals where an undistorted and
noise free signal is essential for example oscilloscope leads BNC plugs are connected with a push
and twist action to disconnect you need to twist and pull
Plugs and sockets are rated by their impedance (50 or 75 ) which must be the same as the
cables impedance
11) D connectors
These are multi-pole connectors with provision for screw fittings to make semi-permanent
connections for example on computer equipment The D shape prevents incorrect connection
Standard D-connectors have 2 rows of contacts (top picture) 9 15 and 25-way versions are the
most popular
12) IDC communication connectors
These multi-pole insulation displacement connectors are used for computer and
telecommunications equipment They automatically cut through the insulation on wires when
installed and special tools are required to fit them They are available as 4 6 and 8-way versions
They are called BT (British Telecom) connectors
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13) USB Connector
The Universal Serial Bus is a serial bus standard to interface devices founded in 1996
Relays
A relay is an electrically operated switch Current flowing through the coil of the relay creates a
magnetic field which attracts a lever and changes the switch contacts The coil current can be on or
off so relays have two switch positions and they are double throw (changeover) switches Relays
allow one circuit to switch a second circuit which can be completely separate from the first For
example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit There is
no electrical connection inside the relay between the two circuits the link is magnetic and
mechanical
Following figure shows a working of relay with its coil and switch contacts You can see a
lever on the left being attracted by magnetism when the coil is switched on This lever moves the
switch contacts There is one set of contacts (SPDT) in the foreground and another behind them
making the relay DPDT
Circuit symbol for a relay Picture of a relay
The relays switch connections are usually labeled COM NC and NO
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COM = Common always connect to this it is the moving part of the switch
NC = Normally Closed COM is connected to this when the relay coil is off
NO = Normally Open COM is connected to this when the relay coil is on
Connect to COM and NO if you want the switched circuit to be on when the relay coil is
on
Connect to COM and NC if you want the switched circuit to be on when the relay coil is
off
Advantages of relays
Relays can switch AC and DC transistors can only switch DC
Relays can switch high voltages transistors cannot
Relays are a better choice for switching large currents (gt 5A)
Relays can switch many contacts at once
Disadvantages of relays
Relays are bulkier than transistors for switching small currents
Relays cannot switch rapidly (except reed relays) transistors can switch many times per
second
Relays use more power due to the current flowing through their coil
Relays require more current than many ICs can provide so a low power transistor may
be needed to switch the current for the relays coil
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductorsmdashthe transformers coils A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic field
through the secondary winding This varying magnetic field induces a varying electromotive force
(EMF) or voltage in the secondary winding This effect is called mutual induction
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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9) Tactile Switch
These switches used in instruments keyboards
Connectors
An electrical connector is a conductive device for joining electrical circuits together The
connection may be temporary as for portable equipment or may require a tool for assembly and
removal or may be a permanent electrical joint between two wires or devices Connectors may join
two lengths of flexible wire or cable or may connect a wire or cable to an electrical terminal
There are hundreds of types of electrical connectors Out of that some of the connecters given
below
1) Battery clips and holders
The standard battery and battery holders such as the 6 times AA cell holder shown Battery holders are
also available with wires attached with pins for PCB mounting or as a complete box with lid
switch and wires
2) Terminal blocks and PCB terminals
Terminal blocks are usually supplied in 12-way lengths but they can be cut into smaller blocks with
a sharp knife large wire cutters or a junior hacksaw They are sometimes called chocolate blocks
because of the way they can be easily cut to size PCB mounting terminal blocks provide an easy
way of making semi-permanent connections to PCBs
PCB Terminal block
terminal
block
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3) Crocodile clips
The standard crocodile clip has no cover and a screw contact However miniature insulated
crocodile clips are more suitable for many purposes including test leads
Crocodile clips
4) 4mm plugs sockets and terminals
These are the standard single pole connectors used on meters and other electronic equipment They
are capable of passing high currents (typically 10A) and most designs are very robust
Plugs
Plugs may have a screw or solder terminal to hold the cable
Sockets
these are usually described as panel mounting because they are designed to be fitted to a case
Terminals
In addition to a socket these have provision for attaching a wire by threading it through a hole (or
wrapping it around the post) and tightening the top nut by hand
4mm terminal and solder tag
5) DC power plugs and sockets
These 2-pole plugs and sockets ensure that the polarity of a DC supply cannot be accidentally
reversed The standard sizes are 21 and 25mm plug diameter Standard plugs have a 10mm shaft
long plugs have a 14mm shaft
6) Jack plugs and sockets
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These are intended for audio signals so mono and stereo versions are available The sizes are
determined by the plug diameter frac14 (63mm) 35mm and 25mm The 25mm size is only
available for mono
frac14 (63mm) jack plug and socket 35mm jack plug and socket 35mm jack line socket
(for fitting to a cable)
35mm jack plug and socket connections
(the R connection is not present on mono plugs)
L = left channel signal R = right channel signal COM = common (0V screen) (Do not use jack
plugs for power supply connections because the contacts may be briefly shorted as the plug is
inserted Use DC power connectors for this)
7) Phono plugs and sockets
These are used for screened cables carrying audio and video signals Stereo connections are made
using a pair of phono plugs and sockets
8) Coax plugs and sockets
These are similar to the phono plugs and sockets described above but they are designed for use with
screened cables carrying much higher frequency signals such as TV aerial leads They provide
better screening because at high frequencies this is essential to reduce electrical noise
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Construction of a screened cable
9) BNC (Bayonet Neill-Concelman) plugs and sockets
These are designed for screened cables carrying high frequency signals where an undistorted and
noise free signal is essential for example oscilloscope leads BNC plugs are connected with a push
and twist action to disconnect you need to twist and pull
Plugs and sockets are rated by their impedance (50 or 75 ) which must be the same as the
cables impedance
11) D connectors
These are multi-pole connectors with provision for screw fittings to make semi-permanent
connections for example on computer equipment The D shape prevents incorrect connection
Standard D-connectors have 2 rows of contacts (top picture) 9 15 and 25-way versions are the
most popular
12) IDC communication connectors
These multi-pole insulation displacement connectors are used for computer and
telecommunications equipment They automatically cut through the insulation on wires when
installed and special tools are required to fit them They are available as 4 6 and 8-way versions
They are called BT (British Telecom) connectors
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13) USB Connector
The Universal Serial Bus is a serial bus standard to interface devices founded in 1996
Relays
A relay is an electrically operated switch Current flowing through the coil of the relay creates a
magnetic field which attracts a lever and changes the switch contacts The coil current can be on or
off so relays have two switch positions and they are double throw (changeover) switches Relays
allow one circuit to switch a second circuit which can be completely separate from the first For
example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit There is
no electrical connection inside the relay between the two circuits the link is magnetic and
mechanical
Following figure shows a working of relay with its coil and switch contacts You can see a
lever on the left being attracted by magnetism when the coil is switched on This lever moves the
switch contacts There is one set of contacts (SPDT) in the foreground and another behind them
making the relay DPDT
Circuit symbol for a relay Picture of a relay
The relays switch connections are usually labeled COM NC and NO
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COM = Common always connect to this it is the moving part of the switch
NC = Normally Closed COM is connected to this when the relay coil is off
NO = Normally Open COM is connected to this when the relay coil is on
Connect to COM and NO if you want the switched circuit to be on when the relay coil is
on
Connect to COM and NC if you want the switched circuit to be on when the relay coil is
off
Advantages of relays
Relays can switch AC and DC transistors can only switch DC
Relays can switch high voltages transistors cannot
Relays are a better choice for switching large currents (gt 5A)
Relays can switch many contacts at once
Disadvantages of relays
Relays are bulkier than transistors for switching small currents
Relays cannot switch rapidly (except reed relays) transistors can switch many times per
second
Relays use more power due to the current flowing through their coil
Relays require more current than many ICs can provide so a low power transistor may
be needed to switch the current for the relays coil
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductorsmdashthe transformers coils A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic field
through the secondary winding This varying magnetic field induces a varying electromotive force
(EMF) or voltage in the secondary winding This effect is called mutual induction
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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3) Crocodile clips
The standard crocodile clip has no cover and a screw contact However miniature insulated
crocodile clips are more suitable for many purposes including test leads
Crocodile clips
4) 4mm plugs sockets and terminals
These are the standard single pole connectors used on meters and other electronic equipment They
are capable of passing high currents (typically 10A) and most designs are very robust
Plugs
Plugs may have a screw or solder terminal to hold the cable
Sockets
these are usually described as panel mounting because they are designed to be fitted to a case
Terminals
In addition to a socket these have provision for attaching a wire by threading it through a hole (or
wrapping it around the post) and tightening the top nut by hand
4mm terminal and solder tag
5) DC power plugs and sockets
These 2-pole plugs and sockets ensure that the polarity of a DC supply cannot be accidentally
reversed The standard sizes are 21 and 25mm plug diameter Standard plugs have a 10mm shaft
long plugs have a 14mm shaft
6) Jack plugs and sockets
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These are intended for audio signals so mono and stereo versions are available The sizes are
determined by the plug diameter frac14 (63mm) 35mm and 25mm The 25mm size is only
available for mono
frac14 (63mm) jack plug and socket 35mm jack plug and socket 35mm jack line socket
(for fitting to a cable)
35mm jack plug and socket connections
(the R connection is not present on mono plugs)
L = left channel signal R = right channel signal COM = common (0V screen) (Do not use jack
plugs for power supply connections because the contacts may be briefly shorted as the plug is
inserted Use DC power connectors for this)
7) Phono plugs and sockets
These are used for screened cables carrying audio and video signals Stereo connections are made
using a pair of phono plugs and sockets
8) Coax plugs and sockets
These are similar to the phono plugs and sockets described above but they are designed for use with
screened cables carrying much higher frequency signals such as TV aerial leads They provide
better screening because at high frequencies this is essential to reduce electrical noise
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Construction of a screened cable
9) BNC (Bayonet Neill-Concelman) plugs and sockets
These are designed for screened cables carrying high frequency signals where an undistorted and
noise free signal is essential for example oscilloscope leads BNC plugs are connected with a push
and twist action to disconnect you need to twist and pull
Plugs and sockets are rated by their impedance (50 or 75 ) which must be the same as the
cables impedance
11) D connectors
These are multi-pole connectors with provision for screw fittings to make semi-permanent
connections for example on computer equipment The D shape prevents incorrect connection
Standard D-connectors have 2 rows of contacts (top picture) 9 15 and 25-way versions are the
most popular
12) IDC communication connectors
These multi-pole insulation displacement connectors are used for computer and
telecommunications equipment They automatically cut through the insulation on wires when
installed and special tools are required to fit them They are available as 4 6 and 8-way versions
They are called BT (British Telecom) connectors
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13) USB Connector
The Universal Serial Bus is a serial bus standard to interface devices founded in 1996
Relays
A relay is an electrically operated switch Current flowing through the coil of the relay creates a
magnetic field which attracts a lever and changes the switch contacts The coil current can be on or
off so relays have two switch positions and they are double throw (changeover) switches Relays
allow one circuit to switch a second circuit which can be completely separate from the first For
example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit There is
no electrical connection inside the relay between the two circuits the link is magnetic and
mechanical
Following figure shows a working of relay with its coil and switch contacts You can see a
lever on the left being attracted by magnetism when the coil is switched on This lever moves the
switch contacts There is one set of contacts (SPDT) in the foreground and another behind them
making the relay DPDT
Circuit symbol for a relay Picture of a relay
The relays switch connections are usually labeled COM NC and NO
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COM = Common always connect to this it is the moving part of the switch
NC = Normally Closed COM is connected to this when the relay coil is off
NO = Normally Open COM is connected to this when the relay coil is on
Connect to COM and NO if you want the switched circuit to be on when the relay coil is
on
Connect to COM and NC if you want the switched circuit to be on when the relay coil is
off
Advantages of relays
Relays can switch AC and DC transistors can only switch DC
Relays can switch high voltages transistors cannot
Relays are a better choice for switching large currents (gt 5A)
Relays can switch many contacts at once
Disadvantages of relays
Relays are bulkier than transistors for switching small currents
Relays cannot switch rapidly (except reed relays) transistors can switch many times per
second
Relays use more power due to the current flowing through their coil
Relays require more current than many ICs can provide so a low power transistor may
be needed to switch the current for the relays coil
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductorsmdashthe transformers coils A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic field
through the secondary winding This varying magnetic field induces a varying electromotive force
(EMF) or voltage in the secondary winding This effect is called mutual induction
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
BASIC ELECTRONICS ENGINEERING 41
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CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 42
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
BASIC ELECTRONICS ENGINEERING 45
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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These are intended for audio signals so mono and stereo versions are available The sizes are
determined by the plug diameter frac14 (63mm) 35mm and 25mm The 25mm size is only
available for mono
frac14 (63mm) jack plug and socket 35mm jack plug and socket 35mm jack line socket
(for fitting to a cable)
35mm jack plug and socket connections
(the R connection is not present on mono plugs)
L = left channel signal R = right channel signal COM = common (0V screen) (Do not use jack
plugs for power supply connections because the contacts may be briefly shorted as the plug is
inserted Use DC power connectors for this)
7) Phono plugs and sockets
These are used for screened cables carrying audio and video signals Stereo connections are made
using a pair of phono plugs and sockets
8) Coax plugs and sockets
These are similar to the phono plugs and sockets described above but they are designed for use with
screened cables carrying much higher frequency signals such as TV aerial leads They provide
better screening because at high frequencies this is essential to reduce electrical noise
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Construction of a screened cable
9) BNC (Bayonet Neill-Concelman) plugs and sockets
These are designed for screened cables carrying high frequency signals where an undistorted and
noise free signal is essential for example oscilloscope leads BNC plugs are connected with a push
and twist action to disconnect you need to twist and pull
Plugs and sockets are rated by their impedance (50 or 75 ) which must be the same as the
cables impedance
11) D connectors
These are multi-pole connectors with provision for screw fittings to make semi-permanent
connections for example on computer equipment The D shape prevents incorrect connection
Standard D-connectors have 2 rows of contacts (top picture) 9 15 and 25-way versions are the
most popular
12) IDC communication connectors
These multi-pole insulation displacement connectors are used for computer and
telecommunications equipment They automatically cut through the insulation on wires when
installed and special tools are required to fit them They are available as 4 6 and 8-way versions
They are called BT (British Telecom) connectors
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13) USB Connector
The Universal Serial Bus is a serial bus standard to interface devices founded in 1996
Relays
A relay is an electrically operated switch Current flowing through the coil of the relay creates a
magnetic field which attracts a lever and changes the switch contacts The coil current can be on or
off so relays have two switch positions and they are double throw (changeover) switches Relays
allow one circuit to switch a second circuit which can be completely separate from the first For
example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit There is
no electrical connection inside the relay between the two circuits the link is magnetic and
mechanical
Following figure shows a working of relay with its coil and switch contacts You can see a
lever on the left being attracted by magnetism when the coil is switched on This lever moves the
switch contacts There is one set of contacts (SPDT) in the foreground and another behind them
making the relay DPDT
Circuit symbol for a relay Picture of a relay
The relays switch connections are usually labeled COM NC and NO
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COM = Common always connect to this it is the moving part of the switch
NC = Normally Closed COM is connected to this when the relay coil is off
NO = Normally Open COM is connected to this when the relay coil is on
Connect to COM and NO if you want the switched circuit to be on when the relay coil is
on
Connect to COM and NC if you want the switched circuit to be on when the relay coil is
off
Advantages of relays
Relays can switch AC and DC transistors can only switch DC
Relays can switch high voltages transistors cannot
Relays are a better choice for switching large currents (gt 5A)
Relays can switch many contacts at once
Disadvantages of relays
Relays are bulkier than transistors for switching small currents
Relays cannot switch rapidly (except reed relays) transistors can switch many times per
second
Relays use more power due to the current flowing through their coil
Relays require more current than many ICs can provide so a low power transistor may
be needed to switch the current for the relays coil
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductorsmdashthe transformers coils A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic field
through the secondary winding This varying magnetic field induces a varying electromotive force
(EMF) or voltage in the secondary winding This effect is called mutual induction
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
BASIC ELECTRONICS ENGINEERING 41
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CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 42
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
BASIC ELECTRONICS ENGINEERING 45
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
BASIC ELECTRONICS ENGINEERING 71
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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Construction of a screened cable
9) BNC (Bayonet Neill-Concelman) plugs and sockets
These are designed for screened cables carrying high frequency signals where an undistorted and
noise free signal is essential for example oscilloscope leads BNC plugs are connected with a push
and twist action to disconnect you need to twist and pull
Plugs and sockets are rated by their impedance (50 or 75 ) which must be the same as the
cables impedance
11) D connectors
These are multi-pole connectors with provision for screw fittings to make semi-permanent
connections for example on computer equipment The D shape prevents incorrect connection
Standard D-connectors have 2 rows of contacts (top picture) 9 15 and 25-way versions are the
most popular
12) IDC communication connectors
These multi-pole insulation displacement connectors are used for computer and
telecommunications equipment They automatically cut through the insulation on wires when
installed and special tools are required to fit them They are available as 4 6 and 8-way versions
They are called BT (British Telecom) connectors
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13) USB Connector
The Universal Serial Bus is a serial bus standard to interface devices founded in 1996
Relays
A relay is an electrically operated switch Current flowing through the coil of the relay creates a
magnetic field which attracts a lever and changes the switch contacts The coil current can be on or
off so relays have two switch positions and they are double throw (changeover) switches Relays
allow one circuit to switch a second circuit which can be completely separate from the first For
example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit There is
no electrical connection inside the relay between the two circuits the link is magnetic and
mechanical
Following figure shows a working of relay with its coil and switch contacts You can see a
lever on the left being attracted by magnetism when the coil is switched on This lever moves the
switch contacts There is one set of contacts (SPDT) in the foreground and another behind them
making the relay DPDT
Circuit symbol for a relay Picture of a relay
The relays switch connections are usually labeled COM NC and NO
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COM = Common always connect to this it is the moving part of the switch
NC = Normally Closed COM is connected to this when the relay coil is off
NO = Normally Open COM is connected to this when the relay coil is on
Connect to COM and NO if you want the switched circuit to be on when the relay coil is
on
Connect to COM and NC if you want the switched circuit to be on when the relay coil is
off
Advantages of relays
Relays can switch AC and DC transistors can only switch DC
Relays can switch high voltages transistors cannot
Relays are a better choice for switching large currents (gt 5A)
Relays can switch many contacts at once
Disadvantages of relays
Relays are bulkier than transistors for switching small currents
Relays cannot switch rapidly (except reed relays) transistors can switch many times per
second
Relays use more power due to the current flowing through their coil
Relays require more current than many ICs can provide so a low power transistor may
be needed to switch the current for the relays coil
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductorsmdashthe transformers coils A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic field
through the secondary winding This varying magnetic field induces a varying electromotive force
(EMF) or voltage in the secondary winding This effect is called mutual induction
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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13) USB Connector
The Universal Serial Bus is a serial bus standard to interface devices founded in 1996
Relays
A relay is an electrically operated switch Current flowing through the coil of the relay creates a
magnetic field which attracts a lever and changes the switch contacts The coil current can be on or
off so relays have two switch positions and they are double throw (changeover) switches Relays
allow one circuit to switch a second circuit which can be completely separate from the first For
example a low voltage battery circuit can use a relay to switch a 230V AC mains circuit There is
no electrical connection inside the relay between the two circuits the link is magnetic and
mechanical
Following figure shows a working of relay with its coil and switch contacts You can see a
lever on the left being attracted by magnetism when the coil is switched on This lever moves the
switch contacts There is one set of contacts (SPDT) in the foreground and another behind them
making the relay DPDT
Circuit symbol for a relay Picture of a relay
The relays switch connections are usually labeled COM NC and NO
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COM = Common always connect to this it is the moving part of the switch
NC = Normally Closed COM is connected to this when the relay coil is off
NO = Normally Open COM is connected to this when the relay coil is on
Connect to COM and NO if you want the switched circuit to be on when the relay coil is
on
Connect to COM and NC if you want the switched circuit to be on when the relay coil is
off
Advantages of relays
Relays can switch AC and DC transistors can only switch DC
Relays can switch high voltages transistors cannot
Relays are a better choice for switching large currents (gt 5A)
Relays can switch many contacts at once
Disadvantages of relays
Relays are bulkier than transistors for switching small currents
Relays cannot switch rapidly (except reed relays) transistors can switch many times per
second
Relays use more power due to the current flowing through their coil
Relays require more current than many ICs can provide so a low power transistor may
be needed to switch the current for the relays coil
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductorsmdashthe transformers coils A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic field
through the secondary winding This varying magnetic field induces a varying electromotive force
(EMF) or voltage in the secondary winding This effect is called mutual induction
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
BASIC ELECTRONICS ENGINEERING 45
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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COM = Common always connect to this it is the moving part of the switch
NC = Normally Closed COM is connected to this when the relay coil is off
NO = Normally Open COM is connected to this when the relay coil is on
Connect to COM and NO if you want the switched circuit to be on when the relay coil is
on
Connect to COM and NC if you want the switched circuit to be on when the relay coil is
off
Advantages of relays
Relays can switch AC and DC transistors can only switch DC
Relays can switch high voltages transistors cannot
Relays are a better choice for switching large currents (gt 5A)
Relays can switch many contacts at once
Disadvantages of relays
Relays are bulkier than transistors for switching small currents
Relays cannot switch rapidly (except reed relays) transistors can switch many times per
second
Relays use more power due to the current flowing through their coil
Relays require more current than many ICs can provide so a low power transistor may
be needed to switch the current for the relays coil
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through
inductively coupled conductorsmdashthe transformers coils A varying current in the first or primary
winding creates a varying magnetic flux in the transformers core and thus a varying magnetic field
through the secondary winding This varying magnetic field induces a varying electromotive force
(EMF) or voltage in the secondary winding This effect is called mutual induction
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
BASIC ELECTRONICS ENGINEERING 48
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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Symbol of transformer
If a load is connected to the secondary an electric current will flow in the secondary winding and
electrical energy will be transferred from the primary circuit through the transformer to the load In
an ideal transformer the induced voltage in the secondary winding (VS) is in proportion to the
primary voltage (VP) and is given by the ratio of the number of turns in the secondary (NS) to the
number of turns in the primary (NP) as follows
By appropriate selection of the ratio of turns a transformer thus allows an alternating current (AC)
voltage to be stepped up by making NS greater than NP or stepped down by making NS less than
NP
Actual pictures of transformer
Types of Transformer
1) Step-up Transformer
2) Step-down Transformer
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CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
BASIC ELECTRONICS ENGINEERING 53
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
BASIC ELECTRONICS ENGINEERING 54
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
BASIC ELECTRONICS ENGINEERING 56
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
BASIC ELECTRONICS ENGINEERING 59
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
BASIC ELECTRONICS ENGINEERING 60
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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CONCLUSION
BASIC ELECTRONICS ENGINEERING 22
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BASIC ELECTRONICS ENGINEERING 23
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
BASIC ELECTRONICS ENGINEERING 60
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 22
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
BASIC ELECTRONICS ENGINEERING 24
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
BASIC ELECTRONICS ENGINEERING 26
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
BASIC ELECTRONICS ENGINEERING 27
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
BASIC ELECTRONICS ENGINEERING 28
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
BASIC ELECTRONICS ENGINEERING 29
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 23
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Department of Electronics amp Telecommunication
Experiment No 02 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
To Study Different Electronics Measuring Components
AIM a) Study of settings of DMM and Measurement of parameters like AC DC voltage
current
b) Study of controls of CRO Measurement of frequency Phase AC and DC Voltages
using CRO
c) Study of controls of Function Generator
a) Study of settings of DMM and Measurement of parameters like AC DC voltages currents
PREREQUISITE
Knowledge of different measuring instruments
Difference between AC DC voltages and currents
Basic concept of diode and transistors
Internal construction of CRO and how it works
Use of function generator and power supply
Basic knowledge of different types of waveforms
OBJECTIVE
Use of DMM for measuring various types of components and parameters
Use of each and every control on front panel of CRO
Use of front panel control of function generator and power supply
EQUIPMENTS amp COMPONENTS
1) Digital Multimeter
2) Connecting Probes
3) Cathode Ray Oscilloscope
4) Function Generator
5) Power Supply
6) Multimeter
BASIC ELECTRONICS ENGINEERING 24
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
BASIC ELECTRONICS ENGINEERING 25
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
BASIC ELECTRONICS ENGINEERING 26
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
BASIC ELECTRONICS ENGINEERING 27
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
BASIC ELECTRONICS ENGINEERING 28
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
BASIC ELECTRONICS ENGINEERING 29
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
BASIC ELECTRONICS ENGINEERING 30
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
BASIC ELECTRONICS ENGINEERING 31
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
BASIC ELECTRONICS ENGINEERING 32
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
BASIC ELECTRONICS ENGINEERING 33
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
BASIC ELECTRONICS ENGINEERING 34
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
BASIC ELECTRONICS ENGINEERING 36
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
BASIC ELECTRONICS ENGINEERING 37
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
BASIC ELECTRONICS ENGINEERING 38
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
BASIC ELECTRONICS ENGINEERING 39
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
BASIC ELECTRONICS ENGINEERING 40
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
BASIC ELECTRONICS ENGINEERING 45
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 24
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THEORY
Digital multimeters are usually referred to as digital-multi-meters abbreviated DMM A
multimeter can be a handheld device useful for basic fault finding and field service work or a bench
instrument which can measure to a very high degree of accuracy Such an instrument will
commonly be found in a calibration lab and can be used to characterize resistance and voltage
standards or adjust and verify the performance of multi-function calibrators
By using mentioned DMM we can measure resistance AC DC voltage and current and diode and
transistor testing
Control Panels
1) LCD Display
A 3 frac12 digit display (maximum reading 1999) indicates measured values and features symbols
indicating ranges low Battery
2) Function Selector
To select ACV DCV ACA DCA RESISTANCE Diode Continuity ampTransistor test
3) Input Jacks
Test leads are inserted into these jacks for voltage resistance current measurements continuity and
diode checks
4) Input socket for transistor test
NPN or PNP transistors are inserted in the sockets provided to measure their ratings
PROCEDURE
1) Measuring voltage and current with DMM-
1 Select a range with a maximum greater than you expect the reading to be
2 Connect the meter making sure the leads are the correct way round
Digital meters can be safely connected in reverse but an analog meter may be damaged
3 If the reading goes off the scale immediately disconnect and select a higher range
2) Testing diode with a DMM-
Digital multimeters have a special setting for testing a diode usually labeled with the diode
symbol
BASIC ELECTRONICS ENGINEERING 25
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
BASIC ELECTRONICS ENGINEERING 26
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
BASIC ELECTRONICS ENGINEERING 27
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
BASIC ELECTRONICS ENGINEERING 28
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
BASIC ELECTRONICS ENGINEERING 29
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
BASIC ELECTRONICS ENGINEERING 30
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
BASIC ELECTRONICS ENGINEERING 31
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
BASIC ELECTRONICS ENGINEERING 32
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
BASIC ELECTRONICS ENGINEERING 33
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
BASIC ELECTRONICS ENGINEERING 34
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
BASIC ELECTRONICS ENGINEERING 35
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
BASIC ELECTRONICS ENGINEERING 36
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
BASIC ELECTRONICS ENGINEERING 37
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
BASIC ELECTRONICS ENGINEERING 38
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
BASIC ELECTRONICS ENGINEERING 39
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
BASIC ELECTRONICS ENGINEERING 40
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
BASIC ELECTRONICS ENGINEERING 41
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CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 42
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BASIC ELECTRONICS ENGINEERING 43
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
BASIC ELECTRONICS ENGINEERING 44
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
BASIC ELECTRONICS ENGINEERING 45
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
BASIC ELECTRONICS ENGINEERING 50
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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Connect the red (+) lead to the anode and the black (-) to the cathode The diode should
conduct and the meter will display a value (usually the voltage across the diode in mV
1000mV = 1V)
Reverse the connections The diode should NOT conduct this way so the meter will display
off the scale (usually blank except for a 1 on the left)
a=anode
k=cathode
3) Testing a transistor with DMM-
Set a digital multimeter to diode test and an analog multimeter to a low resistance range
such as times 10 as described above for testing a diode
The base-emitter (BE) junction should behave like a diode and conduct one way only
The base-collector (BC) junction should behave like a diode and conduct one way only
The collector-emitter (CE) should not conduct either way
The diagram shows how the junctions behave in an NPN transistor The diodes are reversed
in a PNP transistor but the same test procedure can be used
Diodes
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
BASIC ELECTRONICS ENGINEERING 53
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
BASIC ELECTRONICS ENGINEERING 54
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
BASIC ELECTRONICS ENGINEERING 56
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
BASIC ELECTRONICS ENGINEERING 58
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
BASIC ELECTRONICS ENGINEERING 59
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
BASIC ELECTRONICS ENGINEERING 60
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 26
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FRONT PANEL CONTROLS
Measurements
1 Resistance
2 AC Voltage
3 DC Voltage
4 AC Current
5 DC Current
BASIC ELECTRONICS ENGINEERING 27
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
BASIC ELECTRONICS ENGINEERING 28
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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b) Study of controls of CRO Measurement of frequency Phase AC and DC voltages
using CRO
THEORY
The cathode-ray oscilloscope (CRO) is a common laboratory instrument that provides
accurate time and amplitude measurements of voltage signals over a wide range of frequencies Its
reliability stability and ease of operation make it suitable as a general purpose laboratory
instrument The heart of the CRO is a cathode-ray tube shown schematically in Fig1
The cathode ray is a beam of electrons which are emitted by the heated cathode (negative electrode)
and accelerated toward the fluorescent screen The assembly of the cathode intensity grid focus
grid and accelerating anode (positive electrode) is called an electron gun Its purpose is to generate
the electron beam and control its intensity and focus Between the electron gun and the fluorescent
screen there are two pair of metal plates - one oriented to provide horizontal deflection of the beam
and one pair oriented to give vertical deflection to the beam These plates are thus referred to as the
horizontal and vertical deflection plates The combination of these two deflections allows the beam
to reach any portion of the fluorescent screen Wherever the electron beam hits the screen the
phosphor is excited and light is emitted from that point This conversion of electron energy into
light allows us to write with points or lines of light on an otherwise darkened screen
BASIC ELECTRONICS ENGINEERING 28
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
BASIC ELECTRONICS ENGINEERING 29
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
BASIC ELECTRONICS ENGINEERING 31
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
BASIC ELECTRONICS ENGINEERING 32
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
BASIC ELECTRONICS ENGINEERING 33
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
BASIC ELECTRONICS ENGINEERING 34
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
BASIC ELECTRONICS ENGINEERING 35
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
BASIC ELECTRONICS ENGINEERING 36
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
BASIC ELECTRONICS ENGINEERING 37
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
BASIC ELECTRONICS ENGINEERING 38
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
BASIC ELECTRONICS ENGINEERING 40
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
BASIC ELECTRONICS ENGINEERING 45
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 28
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FRONT PANEL DIAGRAM
FRONT PANEL CONTROLS
1) Power ON OFF Push button switches for supplying power to instrument
2) X amp Y-POS Controls horizontal amp vertical position of the trace
3) Time Base -VAR controls the time speed in between two steps of TIMEDIV switch For
calibration put this fully anticlockwise
4) X10 MAG Switch when pushed gives 10 times magnification of the signal X
5) XY Switch when pressed cuts off the time base (XY Display) amp allows access the ext
horizontal signal to be feed through CH2
6) CH-1CH-2 Selects channel from Channel 1 and channel 2
7) MONODUAL Switch selects mono or dual trace operation
8) ALTCHOPADD Switch selects alternate or chopped in DUAL mode If mono is
selected then this switch enable addition or subtraction of channel ie CH1 +-CH2
9) EXT Switch when pressed allows external triggering signal to be feed from the socket
marked TRIGINP
10) LINE switch when pressed display signal synchronized with mains line frequency
11) ALT Selects alternate trigger mode from CH1 amp CH2 In this mode both the signal are
synchronized
12) LEVEL Controls the trigger level from peak to peak amplitude of signal
13) COMPONENT TESTER Switch when pressed starts Component testing operation
14) INTENS Controls the brightness of the trace
15) TR Controls the alignment of the trace with latitude
16) FOCUS Controls the sharpness of the trace
BASIC ELECTRONICS ENGINEERING 29
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
BASIC ELECTRONICS ENGINEERING 31
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
BASIC ELECTRONICS ENGINEERING 32
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
BASIC ELECTRONICS ENGINEERING 33
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
BASIC ELECTRONICS ENGINEERING 34
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
BASIC ELECTRONICS ENGINEERING 35
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
BASIC ELECTRONICS ENGINEERING 36
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
BASIC ELECTRONICS ENGINEERING 37
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
BASIC ELECTRONICS ENGINEERING 38
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
BASIC ELECTRONICS ENGINEERING 39
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
BASIC ELECTRONICS ENGINEERING 40
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
BASIC ELECTRONICS ENGINEERING 41
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CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 42
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BASIC ELECTRONICS ENGINEERING 43
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
BASIC ELECTRONICS ENGINEERING 44
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
BASIC ELECTRONICS ENGINEERING 45
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
BASIC ELECTRONICS ENGINEERING 48
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
BASIC ELECTRONICS ENGINEERING 50
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BASIC ELECTRONICS ENGINEERING 51
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
BASIC ELECTRONICS ENGINEERING 56
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 29
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17) DCACGD Input coupling switch for each channel In AC the signal is coupled through
01MFD capacitor
18) CH1 amp CH 2 BNC connectors serve as input connection for CH 1 and Ch 2 Channel 2
input connections also serve as Horizontal External Signal
19) INV CH2 Switch when pressed invert polarity of CH2
20) DIGITAL READOUT LCD window for displaying digital readout for VDiv amp
TimeDiv Settings
21) VOLTSDIV Switch selects VDiv for channel 1 amp 2
PROCEDURE
1 DC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on DC position
iii) Apply test voltage to CRO input probe
iv) Measure the shift of beam from reference level
v) Calculate the DC voltage
DC Voltage = No of Divisions on Y-Axis VoltsDiv
2 AC Voltage Measurements
i) Adjust beam to reference level
ii) Keep ACDC selector switch on AC position
iii) Apply test voltage to CRO input probe
iv) Measure the peak to peak voltage
v) Calculate the AC voltage
AC Voltage = No of Divisions on Y-Axis VoltsDiv
3 Frequency Measurements
i) Adjust beam to reference level
ii) Apply test voltage to CRO input probe
iii) Measure the time period required to complete one cycle
iv) Calculate the frequency
Frequency = 1 (No of Divisions on X-axis TimeDiv)
4 Phase Measurements
i) Adjust beam to reference level
ii) Apply test voltages to both CRO input channels
iii) Measure the difference between the two waves on X-axis (i e Δt)
iv) Measure the time period required to complete one cycle of channel ndash 1 (ie t1)
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
BASIC ELECTRONICS ENGINEERING 37
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
BASIC ELECTRONICS ENGINEERING 39
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
BASIC ELECTRONICS ENGINEERING 66
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
BASIC ELECTRONICS ENGINEERING 67
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 30
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v) Calculate the Phase
Phase (Φ) = (Δt 180) (t1)
(Channel ndash 2 is having the phase shift of Φ with channel - 1)
Observation Table
Sr No Parameter Actual Value Observed Value
1 DC Voltage
2 AC Voltage
3 Frequency
4 Phase
BASIC ELECTRONICS ENGINEERING 31
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
BASIC ELECTRONICS ENGINEERING 32
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
BASIC ELECTRONICS ENGINEERING 33
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
BASIC ELECTRONICS ENGINEERING 34
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
BASIC ELECTRONICS ENGINEERING 35
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
BASIC ELECTRONICS ENGINEERING 36
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
BASIC ELECTRONICS ENGINEERING 37
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
BASIC ELECTRONICS ENGINEERING 38
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
BASIC ELECTRONICS ENGINEERING 39
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
BASIC ELECTRONICS ENGINEERING 40
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
BASIC ELECTRONICS ENGINEERING 41
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CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 42
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BASIC ELECTRONICS ENGINEERING 43
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
BASIC ELECTRONICS ENGINEERING 44
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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c) Study of controls of Function Generator
THEORY
A function generator is a device that can produce various patterns of voltage at a variety of
frequencies and amplitudes The electrical leads from the device are attached to the ground and
signal input terminals of the device under test
FRONT PANEL CONTROLS
Front panel controls
Waveform key Selects the waveform sine square and triangle
TTL activation Activates TTL output
Numerical keys Specifies frequency
Frequency unit selection Specifies the frequency unit MHz kHz or Hz
Cursor selection Moves the cursor (frequency editing point)left or right
-40db attenuation Attenuates amplitude by-40db
FrequencyVoltage display selection Switches the display between frequency and
voltage
Shift key Selects the 2nd
function associated to the entry keys The LED lights when Shift is
activated
Output OnOff key Turns the output OnOff The LED lights when the output is on
Frequency Editing knob Increases (right turn) or decreases (left turn) the frequency
Main output Outputs sine square and triangle waveform BNC 50 output impedance
TTL output Outputs TTL waveform
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
BASIC ELECTRONICS ENGINEERING 64
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 32
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Amplitude control Sets the sinesquaretriangle waveform amplitude Turn left (decreases)or right
(increase)
DC offset control When pulled out sets the DC offset level for sinesquaretriangle waveform
Turn left (decrease) or right (increase)The range is-5v +5v in 50 load
Duty cycle control When pulled out sets the square or TTL wave duty cycle Turn left
(decrease)or right (increase)
Power switch Turns the main power OnOff
PROCEDURE
1) Connect sinesquaretriangular waveform from function generator to the CRO
2) Take down the various observations by varying the various controls of function generator
on CRO screen
3) Plot the changes in waveform on graph paper
CONCLUSION
BASIC ELECTRONICS ENGINEERING 33
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
BASIC ELECTRONICS ENGINEERING 34
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
BASIC ELECTRONICS ENGINEERING 35
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
BASIC ELECTRONICS ENGINEERING 36
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
BASIC ELECTRONICS ENGINEERING 37
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
BASIC ELECTRONICS ENGINEERING 38
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
BASIC ELECTRONICS ENGINEERING 39
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
BASIC ELECTRONICS ENGINEERING 40
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
BASIC ELECTRONICS ENGINEERING 41
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CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 42
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BASIC ELECTRONICS ENGINEERING 43
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 03 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Regulated Power Supply using Bridge Rectifier Capacitor Filter And
Three Terminal Regulator
AIM a) Identify pins of rectifier diode (Such as 1N4001) and study of its data sheet specification
b) Identify pins of three pin regulator (such as LM 78XX or LM 79XX) and study of its data
sheet specifications
c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
a) Identify pins of rectifier diode(Such as 1N4001)and study of its data sheet specification
PREREQUISITE
Basics of diode rectifier diode
Basics of voltage regulator
Basics of transformer Bridge rectifier
OBJECTIVE
To study working principle of rectifier diode
To study working of voltage regulators
To study amp measure voltages amp observe waveforms of transformer secondary output of
bridge rectifier output regulator
EQUIPMENTS amp COMPONENTS
1) 1N4001
2) Multimeter
3) Trainer kit
4) CRO
5) CRO probes connecting wires
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
BASIC ELECTRONICS ENGINEERING 64
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 34
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THEORY
1N4001 - 1N4007
Figure a Typical Diode
A diode is a two-terminal electronic component with asymmetric transfer characteristic with low
(ideally zero) resistance to current in one direction and high (ideally infinite) resistance in the
other A semiconductor diode the most common type today is a crystalline piece of semiconductor
material with a p-n junction connected to two electrical terminals
Features
Diffused Junction
High Current Capability and Low Forward Voltage Drop
Surge Overload Rating to 30A Peak
Low Reverse Leakage Current
Lead Free Finish
BASIC ELECTRONICS ENGINEERING 35
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
BASIC ELECTRONICS ENGINEERING 36
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
BASIC ELECTRONICS ENGINEERING 37
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
BASIC ELECTRONICS ENGINEERING 38
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
BASIC ELECTRONICS ENGINEERING 39
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
BASIC ELECTRONICS ENGINEERING 40
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
BASIC ELECTRONICS ENGINEERING 41
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CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 42
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BASIC ELECTRONICS ENGINEERING 43
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
BASIC ELECTRONICS ENGINEERING 44
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
BASIC ELECTRONICS ENGINEERING 45
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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Figure b Maxratings of Electrical characteristics of 1N4001 Diode
BASIC ELECTRONICS ENGINEERING 36
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
BASIC ELECTRONICS ENGINEERING 37
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
BASIC ELECTRONICS ENGINEERING 39
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
BASIC ELECTRONICS ENGINEERING 71
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 36
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b) Identify pins of three pin regulator(such as LM 78XX or LM 79XX)and study of its data
sheet specifications
LM 78LXX
The LM78LXX series of three terminal positive regulators is available with several fixed
output voltages making them useful in a wide range of applications When used as a zener
dioderesistor combination replacement the LM78LXX usually results in an effective output
impedance improvement of two orders of magnitude and lower quiescent current These regulators
can provide local on card regulation eliminating
the distribution problems associated with single point regulation
The voltages available allow the LM78LXX to be used in logic systems instrumentation
HiFi and other solid state electronic equipment
The LM78LXX is available in the plastic TO-92 (Z) package
LM 78L05
Features
LM78L05 in micro SMD package
Output voltage tolerances of plusmn5 over the temperature range
Output current of 100 mA
Internal thermal overload protection
Output transistor safe area protection
Internal short circuit current limit
Available in plastic TO-92 and plastic SO-8 low profile packages
No external components
Output voltages of 50V 62V 82V 90V 12V 15V
BASIC ELECTRONICS ENGINEERING 37
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
BASIC ELECTRONICS ENGINEERING 38
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
BASIC ELECTRONICS ENGINEERING 39
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
BASIC ELECTRONICS ENGINEERING 40
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
BASIC ELECTRONICS ENGINEERING 41
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CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 42
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BASIC ELECTRONICS ENGINEERING 43
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
BASIC ELECTRONICS ENGINEERING 44
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
BASIC ELECTRONICS ENGINEERING 45
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
BASIC ELECTRONICS ENGINEERING 48
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
BASIC ELECTRONICS ENGINEERING 50
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BASIC ELECTRONICS ENGINEERING 51
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 37
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Figure c Maxratings of Electrical characteristics of LM78L05
LM78L09
Features
3-Terminal Regulators
Output Current Up to 100 mA
No External Components Required
Internal Thermal-Overload Protection
Internal Short-Circuit Current Limiting
Direct Replacement for Motorola MC79L00
BASIC ELECTRONICS ENGINEERING 38
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
BASIC ELECTRONICS ENGINEERING 39
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
BASIC ELECTRONICS ENGINEERING 40
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 42
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
BASIC ELECTRONICS ENGINEERING 44
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
BASIC ELECTRONICS ENGINEERING 45
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
BASIC ELECTRONICS ENGINEERING 48
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
BASIC ELECTRONICS ENGINEERING 64
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 38
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Theory
This series of fixed negative-voltage integrated-circuit voltage regulators is designed for a
wide range of applications These include on-card regulation for elimination of noise and
distribution problems associated with single-point regulation In addition they can be used to
control series pass elements to make high-current voltage-regulator circuits One of these regulators
can deliver up to 100 mA of output current The internal current-limiting and thermal-shutdown
features make them essentially immune to overload When used as a replacement for a zener-diode
and resistor combination these devices can provide emf current
Figure c Maxratings of Electrical characteristics of LM79L05
BASIC ELECTRONICS ENGINEERING 39
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
BASIC ELECTRONICS ENGINEERING 40
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 42
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BASIC ELECTRONICS ENGINEERING 43
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
BASIC ELECTRONICS ENGINEERING 44
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
BASIC ELECTRONICS ENGINEERING 45
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
BASIC ELECTRONICS ENGINEERING 48
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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BASIC ELECTRONICS ENGINEERING 51
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
BASIC ELECTRONICS ENGINEERING 53
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
BASIC ELECTRONICS ENGINEERING 54
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
BASIC ELECTRONICS ENGINEERING 58
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
BASIC ELECTRONICS ENGINEERING 60
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
BASIC ELECTRONICS ENGINEERING 64
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 39
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c) To measure voltages and observe waveforms at transformer secondary output of bridge
rectifier output regulator
CIRCUIT DIAGRAM
THEORY
For positive half cycle of the input voltage diodes D1 and D2 forward biased and conduct
current During this time diodes D3 and D4 are reverse biased For negative half cycle of the input
voltage diodes D3 and D4 forward biased and conduct current During this time diodes D1and D2
are reverse biased Capacitor C1 and C2 are used as filter capacitor IC 7805 is positive voltage
regulator and Ic 7905 is negative voltage regulator Capacitors C3 and C4 are required if the
regulator is located at an appreciable distance from the power supply filter and capacitors C5 and
C6 are used to improve the transient response of the regulator
PROCEDURE
1 Make the connections as shown in the circuit diagram
2 Vary the load resistance and measure the corresponding load voltage and ripple voltage
values
3 Observe and study the output waveforms on CRO
BASIC ELECTRONICS ENGINEERING 40
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
BASIC ELECTRONICS ENGINEERING 41
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CONCLUSIONS
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BASIC ELECTRONICS ENGINEERING 43
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
BASIC ELECTRONICS ENGINEERING 44
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
BASIC ELECTRONICS ENGINEERING 45
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
BASIC ELECTRONICS ENGINEERING 48
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 40
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OBSERVATION TABLE
Without Filter With Filter
Load
Current
IL(mA)
Load
Voltage
VL (V)
Vm
(V)
Load
current
Il (mA)
Load
Voltage
Vl (mA)
Vrpp
(V)
CALCULATIONS
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CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 42
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
BASIC ELECTRONICS ENGINEERING 45
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 42
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
BASIC ELECTRONICS ENGINEERING 50
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BASIC ELECTRONICS ENGINEERING 51
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
BASIC ELECTRONICS ENGINEERING 53
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
BASIC ELECTRONICS ENGINEERING 54
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
BASIC ELECTRONICS ENGINEERING 60
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
BASIC ELECTRONICS ENGINEERING 64
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 42
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
BASIC ELECTRONICS ENGINEERING 44
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
BASIC ELECTRONICS ENGINEERING 45
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
BASIC ELECTRONICS ENGINEERING 48
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
BASIC ELECTRONICS ENGINEERING 50
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BASIC ELECTRONICS ENGINEERING 51
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
BASIC ELECTRONICS ENGINEERING 53
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
BASIC ELECTRONICS ENGINEERING 54
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
BASIC ELECTRONICS ENGINEERING 56
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
BASIC ELECTRONICS ENGINEERING 58
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
BASIC ELECTRONICS ENGINEERING 59
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
BASIC ELECTRONICS ENGINEERING 60
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 43
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Department of Electronics amp Telecommunication
Experiment No 04 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Bipolar Junction Transistor (BJT)
AIM Single stage BJT Common Emitter amplifier
a To identify pins of a BJT (BC547) and study of its data sheet amp
specifications
b To measure voltages and observe waveforms at input and output
terminals of single stage BJT Common Emitter amplifier circuit
c Calculate voltage gain of the amplifier
PREREQUISITE
Basics of Bipolar Junction Transistor (BJT) amp its biasing methods
Basics of gain of amplifier
OBJECTIVE
To study Characteristics and parameters of BJT
Equipments amp COMPONENTS
1) Transistor 2) Bread Board 3) Function Generator 4) CRO 5) CRO Probes 6) Connecting
Probes
a Identify pins of a BJT (BC547) and study of its data sheet specifications
THEORY
Transistor is a three terminal active device made from different semiconductor materials that can
act as either an insulator or a conductor by the application of a small signal voltage The
transistors ability to change between these two states enables it to have two basic functions
―Switching amp ―amplification (analog electronics)
There are two types of BJT
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 44
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PNP transistor
NPN transistor
The Bipolar Junction Transistorlsquos basic construction consists of two PN-junctions producing three
connecting terminals with each terminal being given a name to identify it from the other two
These three terminals are known and labeled as the Emitter (E) the Base (B) and the Collector (C)
respectively The principle of operation of the two transistor types PNP and NPN is exactly the
same only difference is in their biasing and the polarity of the power supply for each type The
BJT construction is shown in figure1
(a) NPN Transistor (b) PNP Transistor
Figure1BJT Construction
The middle region of each type is called the base of the transistor This region is very thin and
lightly doped The process by which the impurities are added in a pure semiconductor is called
doping The remaining two regions are called emitter and collector The emitter and collector are
heavily doped But the doping level in emitter is slightly greater than that of collector and the
collector region area is slightly more than that of emitter Relative doping levels in the base emitter
and collector junctions must be satisfied to work that device as a transistor Two normal pn-junction
diodes cannot satisfy this requirement
In figure1 the symbol of NPN and PNP transistors are shown Arrow head on a transistor symbol
indicate the conventional current which is opposite to the direction of electron current in emitter
The transistor has two pn-junctions One junction is between the emitter and the base is called
emitter-base junction or simply the emitter junction The other junction is between the base and the
collector and is called collector-base junction or simply collector junction
BASIC ELECTRONICS ENGINEERING 45
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
BASIC ELECTRONICS ENGINEERING 46
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
BASIC ELECTRONICS ENGINEERING 48
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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Bipolar Transistors are current regulating devices that control the amount of current flowing
through them in proportion to the amount of biasing voltage applied to their base terminal acting
like a current-controlled switch
b To measure voltages and observe waveforms at input and output terminals of single
stage BJT Common Emitter amplifier circuit
THEORY
In CE-configuration input is applied between base and emitter and output is taken from collector
and emitter Here emitter of the transistor is common to both input and output circuits and hence
the name common emitter configuration CE-configuration for both NPN and PNP transistor are
shown in figure2
Configurations
(a) NPN Transistor (b) PNP Transistor
Figure2CE-Configuration
Circuit Diagram
As shown in figure 3below the bias voltage VBB forward biases the base-emitter junction and VCC
is used to reverse bias the collector-base junction The input voltage in the CE-configuration is
the base-emitter voltage and the output voltage is the collector-emitter voltage The input current
is IB and the output current is IC
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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BASIC ELECTRONICS ENGINEERING 51
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
BASIC ELECTRONICS ENGINEERING 53
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
BASIC ELECTRONICS ENGINEERING 58
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
BASIC ELECTRONICS ENGINEERING 59
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
BASIC ELECTRONICS ENGINEERING 60
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
BASIC ELECTRONICS ENGINEERING 64
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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Figure3Transistor currents and voltages in CE-Configuration
Characteristics of transistor in CE-Configuration
a Input Characteristics
It is the curve between input current IB (base current) and input voltage VBB (base-emitter
voltage) at constant collector-emitter voltage VCE The base current is taken along Y-axis and
VBB is taken along X-axis as shown in figure4
Figure4Input Characteristics of the transistor in CE-Configuration
From this characteristic we observe the following important points
1 As the input to a transistor in the CE configuration is between the base-to- emitter
junction the CE input characteristics resembles a family of forward biased diode curves
A typical set of CE input characteristics for an npn transistor is shown in figure4
2 For a fixed value of VBE IB decreases as VCE is increased A large value of VCE results in
a large reverse bias at collector-base pn-junction This increases the depletion region and
reduces the effective width of the base Hence there are fewer recombinations in the base
region reducing the base current IB
b Output Characteristics
1 This characteristic shows the relationship between the collector current IC and collector
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
BASIC ELECTRONICS ENGINEERING 48
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
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BASIC ELECTRONICS ENGINEERING 51
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
BASIC ELECTRONICS ENGINEERING 53
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
BASIC ELECTRONICS ENGINEERING 54
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
BASIC ELECTRONICS ENGINEERING 56
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
BASIC ELECTRONICS ENGINEERING 60
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 47
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voltage VCE for various fixed values of IB This characteristic is often called collector
characteristics as shown in figure5
Figure5 Output characteristics of the transistor in CE configuration
2 The value of βdc of the transistor can be found at any point on the characteristics by
taking the ratio IC to IB at that point
βdc = IC IB
3 The output characteristics of CE configuration consists of three regions
a Active Region - the transistor operates as an amplifier and IC = βdcIB
b Saturation - the transistor is fully-ON operating as a switch and
Ic=I(saturation)
c Cut-off - the transistor is fully-OFF operating as a switch and Ic=0
PROCEDURE
a Input Characteristics
Give 10v from power supply 1 to the input side amp 50mv from power supply 2 to
the output side
Vary base current from 0 to 30microA in steps of 5microA by using the input pot amp take
corresponding VBE reading
Repeat the above step for VCE=100mv and VCE=150mv
Plot the graphs corresponding to these set of readings on the graph paper
b Output Characteristics
Apply 10v from power supply 1 to the input side amp adjust IB using input pot to
0microA
Vary the output of power supply 2 ie VCE in steps of 1v from 0 to 15v Take
corresponding IC reading
Repeat the above step for IB=5microA 10microA amp15microA
BASIC ELECTRONICS ENGINEERING 48
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
BASIC ELECTRONICS ENGINEERING 50
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BASIC ELECTRONICS ENGINEERING 51
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
BASIC ELECTRONICS ENGINEERING 53
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
BASIC ELECTRONICS ENGINEERING 54
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
BASIC ELECTRONICS ENGINEERING 56
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
BASIC ELECTRONICS ENGINEERING 58
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
BASIC ELECTRONICS ENGINEERING 59
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
BASIC ELECTRONICS ENGINEERING 60
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 48
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Plot the graphs corresponding to these set of readings on the graph paper
OBSERVATION TABLE
a Input Characteristics
VCE IB microA VBE
50mv
0
5
15
20
25
30
100mv
0
5
15
20
25
30
b Output Characteristics
IB VCE Ic microA
5 microA
0
2
4
6
8
10
10 microA 0
2
4
6
8
10
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
BASIC ELECTRONICS ENGINEERING 50
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BASIC ELECTRONICS ENGINEERING 51
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
BASIC ELECTRONICS ENGINEERING 53
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
BASIC ELECTRONICS ENGINEERING 56
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
BASIC ELECTRONICS ENGINEERING 58
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 49
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c Calculate voltage gain of the amplifier
THEORY
In electronics gain is a measure of the ability of a circuit (often an amplifier) to increase the
power or amplitude of a signal from the input to the output It is usually defined as the mean
ratio of the signal output of a system to the signal input of the same system It may also be
defined on a logarithmic scale in tens of the decimal logarithm of the same ratio (dB gain)
A gain greater than one (zero dB) that is amplification is the defining property of an active
component or circuit while a passive circuit will have a gain of less than one
PROCEDURE
Voltage Gain Measurement
Apply VCC=9v
Adjust the AC input frequency to 10 KHz and connect the source to the circuit
Observe the amplifier output on CRO
Adjust the AC input voltage so as to get maximum undistorted output
Calculate voltage gain AV = VO Vin
Draw the waveform for input and output on graph paper
OBSERVATION TABLE
ip Voltage op Voltage AV = VO Vin dB=20log10AV
CONCLUSION
BASIC ELECTRONICS ENGINEERING 50
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BASIC ELECTRONICS ENGINEERING 51
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
BASIC ELECTRONICS ENGINEERING 53
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
BASIC ELECTRONICS ENGINEERING 54
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
BASIC ELECTRONICS ENGINEERING 56
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
BASIC ELECTRONICS ENGINEERING 58
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
BASIC ELECTRONICS ENGINEERING 59
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
BASIC ELECTRONICS ENGINEERING 64
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
BASIC ELECTRONICS ENGINEERING 56
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 51
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Department of Electronics amp Telecommunication
Experiment No 05 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Operational Amplifier
AIM Op-amp based Summing amplifier and difference amplifier
a) Identify pins of an op-amp (such as LM 741)
b) Implement given voltage equation for two inputs with Op-amp based Summing and
Difference amplifier (such as V0 = 2V1 + 3V2) and V0 = 4V1 ndash V2)
PREREQUISITE
Knowledge of different parameters of op-amp
Brief description of Summing and Difference amplifier
OBJECTIVE
Pin Diagram of LM 741
Application of Summing and Difference amplifier
EQUIPMENTS amp COMPONENTS
1) IC 741
2) Bread board
3) Resistor (As Specified)
4) Connecting wires
5) DC Power supply (+12V)
6) CRO
BASIC ELECTRONICS ENGINEERING 52
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
BASIC ELECTRONICS ENGINEERING 54
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
BASIC ELECTRONICS ENGINEERING 56
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
BASIC ELECTRONICS ENGINEERING 58
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
BASIC ELECTRONICS ENGINEERING 59
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 52
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a) Identify Pins of an Op-amp LM 741
THEORY
The LM 741 is a high performance operational amplifier The high gain and wide range of
operating voltage provides superior performance in many applications
Pin No Pin
Abbreviation
Pin description
1 OFFSET
NULL (-)
Offset voltage is the differential dc voltage required
between the inputs to force the output to zero volts Offset
voltage is nulled by application of a voltage of opposite
polarity to the offset
2 INVERTED
INPUT
All input signals at this pin will be inverted at output pin 6
3 NON-
INVERTED
INPUT
All input signals at this pin will be processed normally
without inversion
4 VEE It is the negative supply voltage terminal Desired operating
range is -5V to -15V
5 OFFSET
NULL (+)
Same as pin 1 except opposite polarity
6 OUTPUT Output voltage polarity will be opposite to that of input
terminal if the input signal is applied at op-amplsquos inverting
point
7 VCC It is the positive supply voltage terminal It specified
operation voltage range is +5V to +15 V
8 NC It stands for NO CONNECTION Nothing is connected to
this pin It is just there to make it standard 8-pin package
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
BASIC ELECTRONICS ENGINEERING 54
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
BASIC ELECTRONICS ENGINEERING 56
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
BASIC ELECTRONICS ENGINEERING 58
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
BASIC ELECTRONICS ENGINEERING 59
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
BASIC ELECTRONICS ENGINEERING 60
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 53
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CIRCUIT DIAGRAM
Fig 51 Symbol of Op-amp 741
Fig 52 Pin Diagram of Op-amp 741
BASIC ELECTRONICS ENGINEERING 54
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
BASIC ELECTRONICS ENGINEERING 56
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
BASIC ELECTRONICS ENGINEERING 58
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
BASIC ELECTRONICS ENGINEERING 59
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
BASIC ELECTRONICS ENGINEERING 60
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
BASIC ELECTRONICS ENGINEERING 64
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 54
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b) Implement given voltage equation for 2 inputs with Op-Amp based Summing and
difference amplifier
THEORY
I Summing Amplifier
It has two or more inputs and its output voltage is proportional to the negative of the
algebraic sum of its input voltages It is also called as ―summing inverter or ―Voltage adder The
amplifier is connected with feedback to produce a closed loop operation
CIRCUIT DIAGRAM
Fig 53 Circuit diagram of Summing Amplifier
Fig 54 Circuit diagram of Summing Amplifier with N inputs
BASIC ELECTRONICS ENGINEERING 55
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Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
BASIC ELECTRONICS ENGINEERING 56
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
BASIC ELECTRONICS ENGINEERING 58
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
BASIC ELECTRONICS ENGINEERING 59
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
BASIC ELECTRONICS ENGINEERING 60
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 55
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Summing Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
Since Vout = -IF RF
Vout = - (I1 + I2) RF
Vout = - (
)
If all the three resistors are equal (R1 = R2 = RF= R) then
Vout = - (
)
Vout = - (Vin1 + Vin2)
General expression for unity gain summing amplifier with N inputs
Vout = - ( )
General expression for gain greater than unity with N inputs
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in
the circuit diagram
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2 mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
BASIC ELECTRONICS ENGINEERING 56
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
BASIC ELECTRONICS ENGINEERING 58
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
BASIC ELECTRONICS ENGINEERING 59
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
BASIC ELECTRONICS ENGINEERING 60
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BASIC ELECTRONICS ENGINEERING 61
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
BASIC ELECTRONICS ENGINEERING 64
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 56
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CALCULATIONS
1 Implement following equation using difference amplifier Vout = - (10V1 + 5V2)
2 Given the value of RF = 10KΩ Therefore
Vout = - (
)
3 Calculate R1 and R2 using the equation
4 From the equation of the output voltage we obtain R1 and R2
5 Implement the values obtained through calculation on the circuit and calculate theoretical as
well as practical values of output voltage
II Difference Amplifier
For the subtraction of two input voltages or to amplify the difference between two voltages
subtractor or Difference amplifier is employed The output voltage is proportional to the difference
between the two input voltages
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
BASIC ELECTRONICS ENGINEERING 58
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
BASIC ELECTRONICS ENGINEERING 59
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
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Shree Ramchandra College of Engineering Lonikand Pune - 412 216
BASIC ELECTRONICS ENGINEERING 61
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 57
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CIRCUIT DIAGRAM
Fig 55 Circuit diagram of Difference amplifier
Difference Amplifier Equation
Applying Kirchhofflsquos current equation at node A (which is virtual ground)
IF = I1 + I2
I1 =
I2 =
IF= ( )
VB = (
)
Summing point VA= VB
If VB =0 then Vout(A) = -V1(
)
BASIC ELECTRONICS ENGINEERING 58
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
BASIC ELECTRONICS ENGINEERING 59
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
BASIC ELECTRONICS ENGINEERING 60
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
BASIC ELECTRONICS ENGINEERING 64
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
BASIC ELECTRONICS ENGINEERING 65
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
BASIC ELECTRONICS ENGINEERING 66
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
BASIC ELECTRONICS ENGINEERING 67
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
BASIC ELECTRONICS ENGINEERING 70
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
BASIC ELECTRONICS ENGINEERING 71
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 58
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If VA = 0 then Vout (B) = -V2(
) (
)
Vout= Vout(A) + Vout(B)
Vout = -V1(
) + V2(
) (
)
When Resistors R1= R2 then
Vout =
( )
PROCEDURE
1 Make the connection for summing amplifier on breadboard as shown in the Fig
53
2 Apply 12 V dual supply to the summing amplifier
3 Apply input voltages as Vin1 = 2mV and Vin2 = 5 mV
4 Measure the value of output voltage using DMM
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
Output voltage
CALCULATIONS
1 Implement following equation using summer amplifier Vout = 4(V1 - V2)
2 Given the value R1= 1KΩ RF = 4KΩ Therefore
Vout =
( )
BASIC ELECTRONICS ENGINEERING 59
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
BASIC ELECTRONICS ENGINEERING 60
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
BASIC ELECTRONICS ENGINEERING 64
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
BASIC ELECTRONICS ENGINEERING 65
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
BASIC ELECTRONICS ENGINEERING 66
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
BASIC ELECTRONICS ENGINEERING 67
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
BASIC ELECTRONICS ENGINEERING 69
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
BASIC ELECTRONICS ENGINEERING 70
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 59
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3 With the help of step 2 and step 3 we will implement the values obtained through
calculation on the circuit and calculate theoretical as well as practical values of output
voltage
CONCLUSION
BASIC ELECTRONICS ENGINEERING 60
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
BASIC ELECTRONICS ENGINEERING 64
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
BASIC ELECTRONICS ENGINEERING 66
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
BASIC ELECTRONICS ENGINEERING 67
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
BASIC ELECTRONICS ENGINEERING 69
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
BASIC ELECTRONICS ENGINEERING 70
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
BASIC ELECTRONICS ENGINEERING 71
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
BASIC ELECTRONICS ENGINEERING 72
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
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BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
BASIC ELECTRONICS ENGINEERING 67
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 61
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Department of Electronics amp Telecommunication
Experiment No 06 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Timer IC 555
AIM Study of Timer IC 555 circuit
a) Identify pins of Timer IC 555
b) Observe output waveform and measure frequency of output wave for Timer IC 555 used
in Astable mode
PREREQUISITE
Knowledge of Timer IC 555
Knowledge of Astable Multivibrator along with derivation of duty cycle
OBJECTIVE
Pin Diagram of Timer IC 555
Working of Astable multivibrator
EQUIPMENTS amp COMPONENTS
1) Timer IC 555
2) Bread board
3) Resistor (As Specified)
4) Capacitor (As Specified)
5) Connecting wires
6) DCPower supply
7) CRO
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
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Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
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Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 62
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a) Identify Pins of TIMER IC 555
THEORY
The connection of the pins for a DIP package as follows
Pin
No
Pin
Abbreviation
Pin description
1 GND Ground All voltages are measured with respect to this
terminal
2 TRIG Trigger it depends upon the amplitude of the external
trigger pulse applied to this pin If the voltage at this pin
is greater than 23 VCC output is LOW and if greater
than 13 VCC then output is HIGH
3 OUT Output Load can be connected between pin 3 and pin
1(ground) or between pin 3 and pin 8 (Supply voltage)
depending upon the nature of output whether high or low
4 RESET Reset Timer IC 555 can be reset (disabled) by applying
negative pulse to this pin If reset not in use it should be
connected to +VCC
5 CTRL Control voltage An external voltage applied to this pin
changes the threshold as well as the trigger voltage
6 THR Threshold It is non inverting input terminal of
comparator which monitors the voltage across the
external capacitor
7 DIS Discharge It is connected internally to the collector of
transistor
8 +VCC Supply Voltage The positive supply voltage between
+5V to +18V with respect to ground
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
BASIC ELECTRONICS ENGINEERING 64
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
BASIC ELECTRONICS ENGINEERING 66
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
BASIC ELECTRONICS ENGINEERING 67
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
BASIC ELECTRONICS ENGINEERING 69
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
BASIC ELECTRONICS ENGINEERING 70
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
BASIC ELECTRONICS ENGINEERING 71
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
BASIC ELECTRONICS ENGINEERING 72
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 63
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CIRCUIT DIAGRAM
Fig 61 Pin Diagram of TIMER IC 555
Fig 62 Internal diagram of TIMER 555 IC
BASIC ELECTRONICS ENGINEERING 64
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
BASIC ELECTRONICS ENGINEERING 65
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
BASIC ELECTRONICS ENGINEERING 66
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
BASIC ELECTRONICS ENGINEERING 67
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
BASIC ELECTRONICS ENGINEERING 69
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
BASIC ELECTRONICS ENGINEERING 70
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
BASIC ELECTRONICS ENGINEERING 71
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
BASIC ELECTRONICS ENGINEERING 72
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 64
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b) Observe waveform and measure frequency of output waveform for Timer IC 555 used in
Astable Mode
THEORY
Timer IC 555 is a timing circuit that can produce an accurate and highly stable time
delays or oscillations Its timing varies from microseconds to hours It operates on +5V to + 18V
supply voltage The timer basically operates in one of the two modes either as Astable (Free
Running) Multivibrator or as Monostable (one shot) Multivibrator
An Astable Multivibrator is a rectangular wave generating circuit It does not require
an external triggering pulse to change the state of the output Hence the name Astable
Multivibrator The time during which output remains high is determined by external resistors
RA and RB and capacitor C
Initially when output is high the capacitor C starts charging towards +VCC through RA
and RB However as soon as voltage across capacitor reaches 23 VCC upper comparator triggers
the Flip-Flop and Output Switches low Now Comparator C starts discharges through RB and
internal discharge transistor When voltage across capacitor reaches 13 VCC Lower comparator
triggers the Flip-Flip and output switches High
CIRCUIT DIAGRAM
Fig 63 Circuit diagram of Astable multivibrator
PROCEDURE
1 Make the connection for Astable multivibrator on breadboard as shown in the circuit
diagram with RA = 1K ohm RB = 2Kohm and C= 01microF
BASIC ELECTRONICS ENGINEERING 65
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
BASIC ELECTRONICS ENGINEERING 66
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
BASIC ELECTRONICS ENGINEERING 67
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
BASIC ELECTRONICS ENGINEERING 69
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
BASIC ELECTRONICS ENGINEERING 70
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
BASIC ELECTRONICS ENGINEERING 71
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
BASIC ELECTRONICS ENGINEERING 72
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 65
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2 Connect DC power supply of 5VConnect CRO at the output terminals of 555 IC and
measure the value of output frequency
3 Sketch the waveforms on graph paper Measure ON and OFF time periods of waveform
on CRO
4 Calculate the Frequency of Oscillations (fO) practically and verify with
theoretical frequency
OBSERVATION TABLE
PARAMETER THEORITICAL PRACTICAL
tON (microsec)
tOFF (microsec)
T (microsec)
FO (KHz)
CALCULATIONS
1 The timing during which capacitor C starts charges from 13 Vcc to 23 Vcc (tC) is
equal the time when output is HIGH (tON) The tON Charge ONlsquo time It is calculated as
tON = tC = 069 (RA +RB) C
2 The timing during which capacitor discharges from 23 Vcc to 13 Vcc(td) is equal to the time
when output is HIGH (tOFF) The tOFF Discharge OFFlsquo time It is calculated as
tOFF = td = 069 (RB) C
3 The total time period (T) of the output waveform is given by
T = tON + tOFF
T= tC + td = 069 (RA + 2RB) C
4 The output frequency (fO) of the output waveform is given as
fO = 1T
BASIC ELECTRONICS ENGINEERING 66
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
BASIC ELECTRONICS ENGINEERING 67
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
BASIC ELECTRONICS ENGINEERING 69
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
BASIC ELECTRONICS ENGINEERING 70
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
BASIC ELECTRONICS ENGINEERING 71
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
BASIC ELECTRONICS ENGINEERING 72
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
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PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
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PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
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Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
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4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
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8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 66
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5 Duty cycle for the Astable multivibrator is the ratio of the ―ON time divided by the
Total time (tON + tOFF) It can be calculated as
Duty cycle = tON (tON + tOFF) = RA + RB
RA + 2RB
CONCLUSION
BASIC ELECTRONICS ENGINEERING 67
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
BASIC ELECTRONICS ENGINEERING 69
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
BASIC ELECTRONICS ENGINEERING 70
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
BASIC ELECTRONICS ENGINEERING 71
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
BASIC ELECTRONICS ENGINEERING 72
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
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The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
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Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 67
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Department of Electronics amp Telecommunication
Experiment No 07 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Digital Circuits
AIM a) Identify pins of Digital Logic Gates ICs such as AND OR NOT XOR NAND
b) Implement Half amp Full adder circuits with basic logic gate ICs
PREREQUISITE
Basic knowledge regarding digital circuits
Knowledge of various binary operations
OBJECTIVE
Identify pins of Digital Logic Gates
Practically building amp testing half adder and full adder circuits
Verification of their respective truth tables
EQUIPMENTS amp COMPONENTS
1) ICs7408 (AND) 7432(OR) 7404(NOT) 7486(EX-OR) 7400(NAND)
7402(NOR)
2) Power Supply
3) Digital trainer Kit
4) Connecting wires etc
BASIC ELECTRONICS ENGINEERING 68
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a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
BASIC ELECTRONICS ENGINEERING 69
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NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
BASIC ELECTRONICS ENGINEERING 70
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b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
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Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
BASIC ELECTRONICS ENGINEERING 72
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The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
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With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 68
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
a) Identify pins of Digital Logic Gates ICs such as ANDORNOTEX-ORNAND
PIN DIAGRAMS
NOT GATE Truth tableY=A
OR GATE Truth tableY=A+B
AND GATE Truth tableY=AB
Input Output
A Y
0 1
1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 1
Inputs Output
A B Y
0 0 0
0 1 0
1 0 0
1 1 1
BASIC ELECTRONICS ENGINEERING 69
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
BASIC ELECTRONICS ENGINEERING 70
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
BASIC ELECTRONICS ENGINEERING 71
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
BASIC ELECTRONICS ENGINEERING 72
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 69
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
NOR GATE Truth table Y=A+B
NAND GATE Truth table Y=AB
EX-OR GATE Truth tableAB+AB
Inputs Output
A B Y
0 0 1
0 1 0
1 0 0
1 1 0
Inputs Output
A B Y
0 0 1
0 1 1
1 0 1
1 1 0
Inputs Output
A B Y
0 0 0
0 1 1
1 0 1
1 1 0
BASIC ELECTRONICS ENGINEERING 70
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
BASIC ELECTRONICS ENGINEERING 71
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
BASIC ELECTRONICS ENGINEERING 72
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 70
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
b) Implement Half amp Full adder circuits with basic logic gate ICs
THEORY
Binary Addition In the binary number system we have only two digits 0lsquo and 1lsquo During the
addition of two binary digits total four cases are involved Let us have binary addition of these four
cases as
Observe carefully these cases What is your observation We see here that Sum=0 When both
inputs are equal (same) and Sum = 1 when inputs are unequal (not same) In digital electronics we
come across a two input gate whose output is 1 for unequal inputs while output is 0 for equal
inputs It is the exclusive-ORlsquo (X-OR) gate It means that X-OR gate has output equal to the sum
of its inputs But this addition is incomplete because it does not produce proper carry as appeared
in the last case The careful observation for producing carry 1lsquo is nothing but AND ing both inputs
Therefore the Boolean expression for sum and carry will be
Sum = A B Carry = AB
The Half Adder Half adder is an electronic circuit which can add two binary digits and producing
its sum with proper carry From the above discussion it is clear that an X-OR gate and an AND gate
is required for its construction The fig 1 shows half adder constructed from one X-OR and single
AND gate
The half adder adds two binary digits but it has a disadvantage that it is not useful during the
addition two binary numbers having more than one binary digit This is because if there is any carry
produced during the addition of LSB there is no provision for such carry in the addition of next
LSB So this circuit can add two single bit binary numbers only
1) 0
+ 0
0 Sum
carry
2) 0
+ 1
1 Sum
3) 1
+ 0
1 Sum
4) 1
+ 1
Carry 1 0 Sum
BASIC ELECTRONICS ENGINEERING 71
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
BASIC ELECTRONICS ENGINEERING 72
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 71
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Circuit diagram for Half adder
TRUTH TABLE FOR HALF ADDER
A B Sum Carry
0 0 0 0
0 1 1 0
1 0 1 0
1 1 0 1
FULL ADDER The full adder is a circuit which can add three binary bits This circuit becomes
essential during the addition of two binary numbers containing more than one bit This is because
the third input is useful carrylsquo generated in the addition of previous binary digits
Now look at the sum of three binary digits given below
There are total eight different possible combinations of inputs but we will consider five of them
which are quite illustrative
1 0 + 0 + 0 = 0 where sum is 0 and carry is 0
2 1 + 0 + 0 = 1 where sum is 1 and carry is 0
3 1 + 1 + 0 = 10 where sum is 0 and carry is 1
4 1 + 0 + 1 = 10 where sum is 0 and carry 1
5 1 + 1 + 1 = 11 where sum is 1 and carry is 1
Basically we have a circuit to add the two binary digits called half adderlsquo To add three
bits we will add the third bit in the addition of sum of the first two binary digits Let us observe
now what happens to this addition if we proceed in this manner
BASIC ELECTRONICS ENGINEERING 72
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 72
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
The first case 0
+ 0
No first carry 0 Sum
+ 0
No second carry 0 Final Sum
Therefore Final sum=0 but final carry = 0
The second case
1
+ 0
No first carry 1 Sum
+ 0
No second carry 1 Final Sum
Therefore final Sum = 1 but final carry = 0
The third case
1
+ 1
First carry 1 0 Sum
+ 0
No second carry 0 final Sum
Therefore final sum = 0 but final carry = 1
The fourth case 1
+ 0
No first carry 1 Sum
+ 1
Second carry 1 0 final Sum
Therefore final sum = 0 but final carry = 1
BASIC ELECTRONICS ENGINEERING 73
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 73
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
The fifth case
1
+ 1
First carry 1 0 Sum
+ 1
Second carry 1 1 final Sum
Therefore final Sum = 1 but final carry = 1
It is observed from these five different sum that final sum is obtained by adding third bit in the sum
of two bits and final carry is obtained by ORing the carries produced at two stages Therefore the
circuit for addition of 3 bits have two half adders and a OR gate having arrangement as shown in
following Figure
Circuit diagram for Full adder
Sum = A B C Carry = AB+AC+BC
INPUT OUT PUT
A B C Sum Carry
0 0 0 0 0
0 0 1 1 0
0 1 0 1 0
0 1 1 0 1
1 0 0 1 0
1 0 1 0 1
1 1 0 0 1
1 1 1 1 1
BASIC ELECTRONICS ENGINEERING 74
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 74
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Half Adder
1) Select one EX-OR gate from IC 7486 and one AND gate from IC 7408
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from AND gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
Full Adder
1) Select two EX-OR gate from IC 7486two AND gate from IC 7408 one OR gate from IC 7432
2) Connect A and B inputs to the inputs of two gates as shown in figure
3) Connect output of both gates to logic indicators
4) Connect supply wires to appropriate pins of each IC
5) Connect both inputs A and B to ground switch on the power supply
6) Note output from X-OR gate as sumlsquo of inputs A and B while output from OR gate as carrylsquo
7) By changing inputs A and B complete the truth table from and observed output states for all
possible combinations of inputs
CONCLUSION
BASIC ELECTRONICS ENGINEERING 75
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 75
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Department of Electronics amp Telecommunication
Experiment No 08 Date of Performance -----------------
Name of the student ---------------------------------------------------------------------------------------------
Division --------------- Roll No ---------------
Soldering Techniques
AIM Build and test an application circuit of IC such as Timer IC 555 Prepare a report on it
PREREQUISITE
Find an importance of soldering in any electronic application
Knowledge of good and bad soldering
OBJECTIVE
To study different soldering techniques
Procedure and precautions to be considered while soldering
EQUIPMENTS amp COMPONENTS
1) Soldering Iron 2) Soldering Metal 3) Flux 4) Timer IC 555 4) DMM 5) CRO
THEORY
Theory for Soldering
What is solder
Solder is an alloy (mixture) of tin and lead typically 60 tin and 40 lead It melts at a
temperature of about 200degC Coating a surface with solder is called tinning because of the tin
content of solder Lead is poisonous and you should always wash your hands after using solder
Solder for electronic components contains tiny cores of flux like the wires inside a mains flux The
flux is corrosive like an acid and it cleans the metal surfaces as the solder melts This is why you
must melt the solder actually on the joint not on the iron tip Without flux most joints would fail
because metals quickly oxidize and the solder itself will not flow properly into dirty oxidized
metal surface The best size of solder for electronics is 22swg (swg = standard wire gauge)
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 76
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Reels of solder
Flux
Flux reacts with or removes oxide and other contamination on the surface to be soldered Dissolve
the metal salts formed during the reaction with the metal oxides Protect the surface from
reoxidation before soldering occurs Provide a thermal blanket to spread the heat evenly during
soldering Reduce the interfacial surface tension between the solder and the substrate in order to
enhance wetting
Flux provides several benefits
bull Cleans the base metal (copper trace)
bull Protects the solder and base metal from oxidizing during the soldering process
bull Promotes wetting action of the melted solder
Flux represents some trade offs
bull Can become entrained in the joint
bull Is corrosive and so must be removed
Soldering Techniques
To achieve a soldered joint the solder and the base metal must be heated above the melting point of
the solder used The method by which the necessary heat is applied depends among other things
on ndash nature and type of the joint melting temperature of the solder and fluxGenerally applied
soldering methods are iron soldering torch soldering mass soldering electrical soldering (high
frequency soldering resistance soldering) furnace soldering and other methods Here we shall
have a closer look at the iron soldering and the mass soldering
1) Iron soldering
2) Mass soldering
a Dip soldering
b Wave soldering
c Drag soldering
BASIC ELECTRONICS ENGINEERING 77
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 77
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
PROCEDURE
Preparing the soldering iron
Place the soldering iron in its stand and plug in
The iron will take a few minutes to reach its operating temperature of about 400degC
Dampen the sponge in the stand
The best way to do this is to lift it out the stand and hold it under a cold tap for a moment
then squeeze to remove excess water It should be damp not dripping wet
Wait a few minutes for the soldering iron to warm up
You can check if it is ready by trying to melt a little solder on the tip
Wipe the tip of the iron on the damp sponge
This will clean the tip
Melt a little solder on the tip of the iron
This is called tinning and it will help the heat to flow from the irons tip to the joint It only
needs to be done when you plug in the iron and occasionally while soldering if you need to
wipe the tip clean on the sponge
You are now ready to start soldering
Hold the soldering iron like a pen near the base of the handle
Imagine you are going to write your name Remember to never touch the hot element or
tip
Touch the soldering iron onto the joint to be made
Make sure it touches both the component lead and the track Hold the tip there for a few
seconds and
Feed a little solder onto the joint
It should flow smoothly onto the lead and track to form a volcano shape as shown in the
diagram Apply the solder to the joint not the iron
Remove the solder then the iron while keeping the joint still
Allow the joint a few seconds to cool before you move the circuit board
Inspect the joint closely
It should look shiny and have a volcano shape If not you will need to reheat it and feed in
a little more solder This time ensure that both the lead and track are heated fully before
applying solder
BASIC ELECTRONICS ENGINEERING 78
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 78
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Good Soldering Bad Soldering
Using a heat sink
Some components such as transistors can be damaged by heat when soldering so if you are not an
expert it is wise to use a heat sink clipped to the lead between the joint and the component body
You can buy a special tool but a standard crocodile clip works just as well and is cheaper
Crocodile clip
How to solder Actual components on board
Soldering Advice for Components
It is tempting to start soldering components onto the circuit board straight away but please take
time to identify all the parts first You are much less likely to
make a mistake if you do this
1 Stick all the components onto a sheet of paper using
sticky tape
2 Identify each component and write its name or value
beside it
3 Add the code (R1 R2 C1 etc) if necessary
Many projects from books and magazines label the
components with codes (R1 R2 C1 D1 etc) and you
should use the projects parts list to find these codes if they are given
BASIC ELECTRONICS ENGINEERING 79
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 79
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
4 Resistor values can be found using the resistor colour code which is explained on our
Resistors page You can print out and make your own Resistor Colour Code Calculator to
help you
5 Capacitor values can be difficult to find because there are many types with different
labelling systems The various systems are explained on our Capacitors page
For most projects it is best to put the components onto the board in the order given below
Components Pictures Reminders and Warnings
1 IC Holders
(DIL sockets)
Connect the correct way round by
making sure the notch is at the correct end
Do NOT put the ICs (chips) in yet
2 Resistors
No special precautions are needed with
resistors
3
Small value
capacitors
(usually less than
1microF)
These may be connected either way round
Take care with polystyrene capacitors
because they are easily damaged by heat
4
Electrolytic
capacitors
(1microF and greater)
Connect the correct way round They
will be marked with a + or - near one lead
5 Diodes
Connect the correct way round
Take care with germanium diodes (eg
OA91) because they are easily damaged
by heat
6 LEDs
Connect the correct way round
The diagram may be labelled a or + for
anode and k or - for cathode yes it really
is k not c for cathode The cathode is the
short lead and there may be a slight flat on
the body of round LEDs
7 Transistors
Connect the correct way round
Transistors have 3 legs (leads) so extra
care is needed to ensure the connections
are correct Easily damaged by heat
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 80
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
8
Wire Links
between points on
the circuit board
single core wire
Use single core wire this is one solid wire
which is plastic-coated
If there is no danger of touching other
parts you can use tinned copper wire this
has no plastic coating and looks just like
solder but it is stiffer
9
Wires to parts off
the circuit board
including switches
relays
variable resistors
and loudspeakers
stranded wire
You should use stranded wire which is
flexible and plastic-coated Do not use
single core wire because this will break
when it is repeatedly flexed
De-soldering
At some stage you will probably need to desolder a joint to remove or re-position a wire or
component There are two ways to remove the solder
Using a desoldering pump (solder sucker)
1 With a desoldering pump (solder sucker)
Set the pump by pushing the spring-loaded plunger down until it locks Apply both the
pump nozzle and the tip of your soldering iron to the joint
Wait a second or two for the solder to melt
Then press the button on the pump to release the plunger and suck the molten solder into
the tool
Repeat if necessary to remove as much solder as possible
The pump will need emptying occasionally by unscrewing the nozzle
BASIC ELECTRONICS ENGINEERING 81
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 81
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
With solder remover wick (copper braid)
Solder remover wick
Apply both the end of the wick and the tip of your soldering iron to the joint
As the solder melts most of it will flow onto the wick away from the joint
Remove the wick first then the soldering iron
Cut off and discard the end of the wick coated with solder
After removing most of the solder from the joint(s) you may be able to remove the wire or
component lead straight away (allow a few seconds for it to cool) If the joint will not come apart
easily apply your soldering iron to melt the remaining traces of solder at the same time as pulling
the joint apart taking care to avoid burning yourself
Precautions
First a few safety precautions
Never touch the element or tip of the soldering iron
They are very hot (about 400degC) and will give you a nasty burn
Take great care to avoid touching the mains flux with the tip of the iron
The iron should have a heatproof flex for extra protection An ordinary plastic flux will
melt immediately if touched by a hot iron and there is a serious risk of burns and electric
shock
Always return the soldering iron to its stand when not in use
Never put it down on your workbench even for a moment
Work in a well-ventilated area
The smoke formed as you melt solder is mostly from the flux and quite irritating Avoid
breathing it by keeping you head to the side of not above your work
BASIC ELECTRONICS ENGINEERING 82
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS
BASIC ELECTRONICS ENGINEERING 82
Shree Ramchandra College of Engineering Lonikand Pune - 412 216
Wash your hands after using solder
Solder contains lead which is a poisonous metal
First Aid for Burns
Most burns from soldering are likely to be minor and treatment is simple
Immediately cool the affected area under gently running cold water
Keep the burn in the cold water for at least 5 minutes (15 minutes is recommended) If ice
is readily available this can be helpful too but do not delay the initial cooling with cold
water
Do not apply any creams or ointments
The burn will heal better without them A dry dressing such as a clean handkerchief may
be applied if you wish to protect the area from dirt
Seek medical attention if the burn covers an area bigger than your hand
To reduce the risk of burns
Always return your soldering iron to its stand immediately after use
Allow joints and components a minute or so to cool down before you touch them
Never touch the element or tip of a soldering iron unless you are certain it is cold
CONCLUSIONS