Unit – IV

SPECIAL PURPOSE ELECTRONIC DEVICES

TUNNEL DIODE

A Tunnel diode is a heavily doped p-n junction diode in which the electric current decreases as

the voltage increases. In tunnel diode, electric current is caused by “Tunnelling”. The tunnel diode is used

as a very fast switching device in computers.

A tunnel diode is also known as Esaki diode which is named after Leo Esaki for his work on the tunnelling

effect. The operation of tunnel diode depends on the quantum mechanics principle known as “Tunnelling”.

In electronics, tunnelling means a direct flow of electrons across the small depletion region from n-side

conduction band into the p-side valence band.

The germanium material is commonly used to make the tunnel diodes. They are also made from other types

of materials such as gallium arsenide, gallium antimonide, and silicon.

The circuit symbol of tunnel diode is shown in the below figure. In tunnel diode, the p-type

semiconductor act as an anode and the n-type semiconductor act as a cathode.

In tunnel diode, the p-type and n-type semiconductor is heavily doped which means a large number of

impurities are introduced into the p-type and n-type semiconductor. This heavy doping process produces

an extremely narrow depletion region. The concentration of impurities in tunnel diode is 1000 times greater

than the normal p-n junction diode.

Unlike the normal p-n junction diode, the width of a depletion layer in tunnel diode is extremely narrow.

So applying a small voltage is enough to produce electric current in tunnel diode.

Working of Tunnel diode

Unbiased tunnel diode

When no voltage is applied to the tunnel diode, it is said to be an unbiased tunnel diode. In tunnel diode,

the conduction band of the n-type material overlaps with the valence band of the p-type material because

of the heavy doping.

Because of this overlapping, the conduction band electrons at n-side and valence band holes at p-side are

nearly at the same energy level. So when the temperature increases, some electrons tunnel from the

conduction band of n-region to the valence band of p-region. In a similar way, holes tunnel from the valence

band of p-region to the conduction band of n-region. However, the net current flow will be zero because an

equal number of charge carriers (free electrons and holes) flow in opposite directions.

Small voltage applied to the tunnel diode

When a small voltage is applied to the tunnel diode which is less than the built-in voltage of the depletion

layer, no forward current flows through the junction.

However, a small number of electrons in the conduction band of the n-region will tunnel to the empty states

of the valence band in p-region. This will create a small forward bias tunnel current. Thus, tunnel current

starts flowing with a small application of voltage.

Applied voltage is slightly increased

When the voltage applied to the tunnel diode is slightly increased, a large number of free electrons at n-

side and holes at p-side are generated. Because of the increase in voltage, the overlapping of the conduction

band and valence band is increased.

In simple words, the energy level of an n-side conduction band becomes exactly equal to the energy level

of a p-side valence band. As a result, maximum tunnel current flows.

Applied voltage is further increased

If the applied voltage is further increased, a slight misalign of the conduction band and valence band takes

place.

Since the conduction band of the n-type material and the valence band of the p-type material sill overlap.

The electrons tunnel from the conduction band of n-region to the valence band of p-region and cause a

small current flow. Thus, the tunneling current starts decreasing.

Applied voltage is largely increased

If the applied voltage is largely increased, the tunneling current drops to zero. At this point, the conduction

band and valence band no longer overlap and the tunnel diode operates in the same manner as a normal p-

n junction diode.

If this applied voltage is greater than the built-in potential of the depletion layer, the regular forward current

starts flowing through the tunnel diode.

The portion of the curve in which current decreases as the voltage increases is the negative resistance region

of the tunnel diode. The negative resistance region is the most important and most widely used characteristic

of the tunnel diode.

A tunnel diode operating in the negative resistance region can be used as an amplifier or an oscillator.

V-I CHARACTERISTICS

Advantages of tunnel diodes

Long life

High-speed operation

Low noise

Low power consumption

Disadvantages of tunnel diodes

Tunnel diodes cannot be fabricated in large numbers

Being a two terminal device, the input and output are not isolated from one another.

Applications of tunnel diodes

Tunnel diodes are used as logic memory storage devices.

Tunnel diodes are used in relaxation oscillator circuits.

Tunnel diode is used as an ultra high-speed switch.

Tunnel diodes are used in FM receivers.

PIN DIODE The diode in which the intrinsic layer of high resistivity is sandwiched between the P and N-region

of semiconductor material such type of diode is known as the PIN diode. The high resistive layer of the

intrinsic region provides the large electric field between the P and N-region. The electric field induces

because of the movement of the holes and the electrons. The direction of the electric field is from n-region

to p-region.

PIN Diode Structure

The diode consists the P-region and N-region which is separated by the intrinsic semiconductor

material. In P-region the hole is the majority charge carrier while in n-region the electron is the majority

charge carrier. The intrinsic region has no free charge carrier. It acts as an insulator between n and the p-

type region. The i-region has the high resistance which obstructs the flow of electrons to pass through it.

Working of PIN Diode

The working of the PIN diode is similar to the ordinary diode. When the diode is unbiased, their charge

carrier will diffuse. The word diffusion means the charge carriers of the depletion region try to move to

their region. The process of diffusion occurs continue until the charges become equilibrium in the depletion

region.

Let the N and I-layer make the depletion region. The diffusion of the hole and electron across the region

generates the depletion layer across the NI-region. The thin depletion layer induces across n-region, and

thick depletion region of opposite polarity induces across the I-region.

Forward Biased PIN Diode

When the diode is kept forward biased, the charges are continuously injected into the I-region from the P

and N-region. This reduces the forward resistance of the diode, and it behaves like a variable resistance.

The charge carrier which enters from P and N-region into the i-region are not immediately combined into

the intrinsic region. The finite quantity of charge stored in the intrinsic region decreases their resistivity.

Consider the Q be the quantity of charge stored in the depletion region. The τ is the time used for the

recombination of the charges. The quantity of the charges stored in the intrinsic region depends on their

recombination time. The forward current starts flowing into the I region.

Where,IF –forwardcurrent

τ- recombination time

Reversed Biased PIN Diode

When the reverse voltage is applied across the diode, the width of the depletion region increases. The

thickness of the region increases until the entire mobile charge carrier of the I-region swept away from

it. The reverse voltage requires for removing the complete charge carrier from the I-region is known

as the swept voltage. In reverse bias, the diode behaves like a capacitor. The P and N region acts as the positive and negative

plates of the capacitor, and the intrinsic region is the insulator between the plates.

Where, A – junction diode

w – intrinsic region thickness

PIN DIODE CHARACTERISTICS

There are a number of PIN diode characteristics that set this diode apart from other forms of diode. These

key PIN diode characteristics include the following:

High breakdown voltage: The wide depletion layer provided by the intrinsic layer ensures that

PIN diodes have a high reverse breakdown characteristic.

Low capacitance: Again the intrinsic layer increases the depletion region width. As the

capacitance of a capacitor reduces with increasing separation, this means that a PIN diode will have

a lower capacitance as the depletion region will be wider than a conventional diode. This PIN diode

characteristic can have significant advantages in a number of RF applications - for example when a

PIN diode is used as an RF switch.

Carrier storage: Carrier storage gives a most useful PIN diode characteristic. For small signals at

high frequencies the stored carriers within the intrinsic layer are not completely swept by the RF

signal or recombination. At these frequencies there is no rectification or distortion and the PIN diode

characteristic is that of a linear resistor which introduces no distortion or rectification. The PIN

diode resistance is governed by the DC bias applied. In this way it is possible to use the device as

an effective RF switch or variable resistor for an attenuator producing far less distortion than

ordinary PN junction diodes.

Sensitive photo detection: By having a larger depletion region - as in the case of a PIN diode - the

volume for light reception is increased. This makes PIN diodes ideal for use as photo detectors.

PIN DIODE USES AND ADVANTAGES

The PIN diode is used in a number of areas as a result of its structure proving some properties which are of

particular use.

High voltage rectifier: The PIN diode can be used as a high voltage rectifier. The intrinsic region

provides a greater separation between the PN and N regions, allowing higher reverse voltages to be

tolerated.

RF switch: The PIN diode makes an ideal RF switch. The intrinsic layer between the P and N

regions increases the distance between them. This also decreases the capacitance between them,

thereby increasing he level of isolation when the diode is reverse biased.

Photo detector: As the conversion of light into current takes place within the depletion region of

a photo diode, increasing the depletion region by adding the intrinsic layer improves the

performance by increasing he volume in which light conversion occurs.

POINT CONTACT DIODE

Point contact diode is formed by touching a metallic wire with an N-type semiconductor to form a small

area of contact. This forms a small point junction. It is widely used because such a small point junction

possesses a small value of junction capacitance. Thus, the charge storage at the junction is low. Due to this,

the switching ability of diode is much better than a conventional diode.

Construction of Point Contact Diode

It is formed by a contact of an N-type semiconductor substrate and tungsten or phosphor bronze wire (Cat

whisker). The semiconductor used in the construction of point contact diode can be either silicon or

germanium but Germanium is used extensively because it possesses higher carrier mobility.

The tungsten wire is joined to N-type semiconductor but the phase of the substrate joined to cat whisker

should be opposite to that of metal contact phase. The anode and cathode terminal are connected through

metallic contacts.

Working of Point Contact Diode

When forward bias is applied to point contact diode the current produced in the device is passed through

the cat whisker. Due to this, the tungsten wire gets heated. Due to this heating, the wire undergoes

deformation. Thus, a small gap is deliberately left for the expansion of wire under the large current.

When the wire gets heated, the semiconductor in the contact with the wire also gets heated. Due to this, it

gets melted and atoms from whisker are passed to semiconductor crystal. Thus, the whisker acts as a P-type

semiconductor. Therefore, a P-N Junction is formed but the area of the junction is very small. It can be

assumed as a pointed junction.

Although the junction cannot be seen clearly because the size of the junction is very small, it can be

considered as point junction. The entire device is enclosed in glass or ceramic envelope. Besides, the

supporting structure is provided to N-type semiconductor and cat whisker to provide mechanical strength

to the device.

The junction capacitance and diffused capacitance in this diode is very small i.e. about 0.1 to 1pF. This is

because the area of contact between the wire and the N-type substrate is very small. Due to the small area

of junction the density of charge carriers near junction is very low. Thus, the low charge storage imparts it

the ability to switch fastly.

Advantages of Point Contact Diode

1. Suitable for High Frequency: Due to fast switching, it is suitable for high-frequency applications.

Disadvantages of Point Contact Diode

1. Lower Current Rating: The diode has lower current rating due to which the diode resistance is

large under forward bias.

2. Less Reliable: The small area of contact is not very rugged and thus, it is less reliable than a

conventional diode.

Applications of Point Contact Diode

1. High-Frequency Circuits: Due to small junction area and low junction capacitance and diffused

capacitance as discussed above, the diode is suitable for high-frequency applications (about 10

GHz).

2. Radio Frequency Mixers: In communication, Mixers play a crucial role in circuitry and the point

contact diode is used extensively in radio frequency mixers.

3. Detector Circuits: For detecting high-frequency signal these diodes play a crucial role in circuitry.

4. Video Detector: It also finds application in video detector.

5. Envelope detector and detector circuits of radio and television: Point contact diodes are also

used in envelope and television detector circuit because it switches rapidly from one state to another

state.

SILICON CONTROLLED RECTIFIER Thyristor or silicon controlled rectifier is a multilayer semiconductor device and is similar to the

transistor. Silicon controlled rectifier consists of three terminals (anode, cathode, and gate) unlike the two

terminal diode (anode and cathode) rectifier. The diodes are termed as uncontrolled rectifiers as they

conduct (during forward bias condition without any control) whenever the anode voltage of the diode is

greater than cathode voltage.

But, the silicon controlled rectifiers doesn’t conduct even though the anode voltage is greater than the

cathode voltage unless until the (third terminal) gate terminal is triggered. Thus, by providing the triggering

pulse (firing) to the gate terminal, we can control the operation (ON or OFF) of thyristor. Hence, the

thyristor is also called as controlled rectifier or silicon controlled rectifier.

Unlike two layers (P-N) in the diode and three layers (P-N-P or N-P-N) in transistors, the silicon controlled

rectifier consists of four layers (P-N-P-N) with three P-N junctions that are connected in series. The silicon

controlled rectifier or thyristor is represented by the symbol as shown in the figure.

Silicon Controlled Rectifier

Silicon Controlled Rectifier Working

The thyristor working can be understood by considering the three states modes of operation of silicon

controlled rectifier. The three modes of operation of thyristor are as follows:

Reverse blocking mode

Forward blocking mode

Forward conducting mode

Reverse Blocking Mode

If we reverse the anode and cathode connections of the thyristors, then the lower and upper diodes are

reverse biased. Thus, there is no conduction path, so no current will flow. Hence, is called as reverse

blocking mode.

Forward Blocking Mode

In general, without any triggering pulse to gate terminal, silicon controlled rectifier remains switched off,

indicating no current flow in the forward direction (from anode to cathode). This is because, we connected

two diodes (both upper and lower diodes are forward biased) together to form a thyristor. But, the junction

between these two diodes is reverse biased, which eliminates the flow of current from top to bottom. Hence,

this state is termed as forward blocking mode. In this mode, even though thyristor is having condition like

a conventional forward biased diode, it will not conduct as the gate terminal is not triggered.

Forward Conducting Mode

In this forward conducting mode, the anode voltage must be greater than the cathode voltage and the third

terminal gate must be triggered appropriately for the conduction of the thyristor. This is because, whenever

the gate terminal is triggered, then the lower transistor will conduct which switches on the upper transistor

and then the upper transistor switches on the lower transistor and thus the transistors activates each other.

This process of internal positive feedback of both the transistors repeats until both gets fully activated and

then the current will from anode to cathode. So, this mode of operation of silicon controlled rectifier is

called as forward conduction mode.

SCR-Volt-ampere-Characteristics

As already mentioned, the SCR is a four-layer device with three terminals, namely, the anode, the cathode

and the gate. When the anode is made positive with respect to the cathode, junctions J1 and J3 are forward

biased and junction J2 is reverse-biased and only the leakage current will flow through the device. The SCR

is then said to be in the forward blocking state or in the forward mode or off state. But when the cathode is

made positive with respect to the anode, junctions J1 and J3 are reverse-biased, a small reverse leakage

current will flow through the SCR and the SGR is said to be in the reverse blocking state or in reverse

mode.

When the anode is positive with respect to cathode i.e. when the SCR is in forward mode, the SCR does

not conduct unless the forward voltage exceeds certain value, called the forward breakover voltage, VFB0.

In non-conducting state, the current through the SCR is the leakage current which is very small and is

negligible. If a positive gate current is supplied, the SCR can become conducting at a voltage much lesser

than forward break-over voltage. The larger the gate current, lower the break-over voltage. With sufficiently

large gate current, the SCR behaves identical to PN rectifier. Once the SCR is switched on, the forward

voltage drop across it is suddenly reduced to very small value, say about 1 volt. In the conducting or on-

state, the current through the SCR is limited by the external impedance.

When the anode is negative with respect to cathode, that is when the SCR is in reverse mode or in blocking

state no current flows through the SCR except very small leakage current of the order of few micro-amperes.

But if the reverse voltage is increased beyond a certain value, called the reverse break-over voltage,

VRB0 avalanche break down takes place. Forward break-over voltage VFB0 is usually higher than reverse

breakover voltage,VRBO.

The switching action of gate takes place only when (i) SCR is forward biased i.e. anode is positive with respect to cathode, and

(ii) Suitable positive voltage is applied between the gate and the cathode.

The SCR can be switched off by reducing the forward current below the level of holding current which

may be done either by reducing the applied voltage or by increasing the circuit impedance.

Note : The gate can only trigger or switch-on the SCR, it cannot switch off.

Normally SCRs have high switching speed and can handle heavy current flow. This makes them ideal for

many applications like

1. Power switching circuits (for both AC and DC)

2. Zero-voltage switching circuits

3. Over voltage protection circuits

4. Controlled Rectifiers

5. Inverters

6. AC Power Control (including lights, motors, etc.)

7. Pulse Circuits

8. Battery Charging Regulator

9. Latching Relays

UJT (UNI-JUNCTION TRANSISTOR)

Uni-junction transistor is also known as double-base diode because it is a 2-layered, 3-terminal solid-state

switching device. It has only one junction so it is called as a uni-junction device. The unique characteristic

feature of this device is such that when it is triggered, the emitter current increases until it is restricted by

an emitter power supply.

Construction of UJT

UJT is a three-terminal, single-junction, two-layered device, and it is similar to a thyristor compare to

a transistors.

The silicon bar has two Ohmic contacts designated as base1 and base2, as shown in the fig. The function

of the base and the emitter are different from the base and emitter of a bipolar transistor.

The emitter is of P-type, and it is heavily doped. The resistance between B1 and B2 when the emitter is

open-circuited is called an inter-base resistance. The emitter junction is usually situated closer to the base

B2 than the base B1. So the device is not symmetrical, because symmetrical unit does not provide electrical

characteristics to most of the applications.

Operation of a UJT

Imagine that the emitter supply voltage is turned down to zero. Then the intrinsic stand-off voltage reverse-

biases the emitter diode, as mentioned above. If VB is the barrier voltage of the emitter diode, then the total

reverse bias voltage is VA + VB = Ƞ VBB + VB. For silicon VB = 0.7 V.

Now let the emitter supply voltage VE be slowly increased. When VE becomes equal to Ƞ VBB, IE will be

reduced to zero. With equal voltage levels on each side of the diode, neither reverse nor forward current

will flow. When emitter supply voltage is further increased, the diode becomes forward-biased as soon as

it exceeds the total reverse bias voltage(Ƞ VBB + VB). This value of emitter voltage VE is called the peak-

point voltage and is denoted by VP. When VE = VP, emitter current IE starts to flow through RB1 to ground,

that is B1. This is the minimum current that is required to trigger the UJT. This is called the peak-point

emitter current and denoted by IP. Ip is inversely proportional to the inter base voltage, VBB. Now when the

emitter diode starts conducting, charge carriers are injected into the RB region of the bar. Since the

resistance of a semiconductor material depends upon doping, the resistance of region RB decreases rapidly

due to additional charge carriers (holes). With this decrease in resistance, the voltage drop across RB also

decreases, because the emitter diode to be more heavily forward biased. This, in turn, results in larger

forward current, and consequently more charge carriers are injected causing still further reduction in the

resistance of the RB region. Thus the emitter current goes on increasing until it is limited by the emitter

power supply. Since VA decreases with the increase in emitter current, the UJT is said to have negative

resistance characteristic. It is seen that the base-2 (B2) is used only for applying external voltage VBB

across it. Terminals E and B1 are the active terminals. UJT is usually triggered into conduction by applying

a suitable positive pulse to the emitter. It can be turned off by applying a negative trigger pulse.

For a unijunction transistor, the resistive ratio of RB1 to RBB shown above is called

the intrinsic stand-off ratio and is given the Greek symbol: η (eta). Typical standard

values of η range from 0.5 to 0.8 for most common UJT’s.

UJT Characteristics

The static emitter characteristic (a curve showing the relation between emitter voltage VE and emitter

current IE) of a UJT at a given inter base voltage VBB is shown in figure. From figure it is noted that for

emitter potentials to the left of peak point, emitter current IE never exceeds IE. The current IE corresponds

very closely to the reverse leakage current ICo of the conventional BJT. This region, as shown in the figure,

is called the cut-off region. Once conduction is established at VE = VP the emitter potential VE starts

decreasing with the increase in emitter current IE. This Corresponds exactly with the decrease in resistance

RB for increasing current IE. This device, therefore, has a negative resistance region which is stable enough

to be used with a great deal of reliability in the areas of applications listed earlier. Eventually, the valley

point reaches, and any further increase in emitter current IE places the device in the saturation region, as

shown in the figure. Three other important parameters for the UJT are IP, VV and IV and are defined below:

Peak-Point Emitter Current. Ip. It is the emitter current at the peak point. It represents the minimum

current that is required to trigger the device (UJT). It is inversely proportional to the inter base voltage VBB.

Valley Point Voltage VV The valley point voltage is the emitter voltage at the valley point. The valley

voltage increases with the increase in inter base voltage VBB.

Valley Point Current IV The valley point current is the emitter current at the valley point. It increases with

the increase in inter-base voltage VBB.

Applications of UJT

1. Used as Relaxation oscillator.

2. Used as Voltage regulator.

3. Used as switching circuit.

4. Widely used as triggering device for silicon control rectifiers(SCR).

5. Used as phase control circuit.

6. Used as timing circuit.

7. Used in saw tooth generator.

8. Used to generate magnetic flux.

SCHOTTKY DIODE Schottky diode is a metal-semiconductor junction diode that has less forward voltage drop than the P-

N junction diode and can be used in high-speed switching applications.

In schottky diode, metals such as aluminum or platinum replace the P-type semiconductor. The

schottky diode is named after German physicist Walter H. Schottky.

Schottky diode is also known as schottky barrier diode, surface barrier diode, majority carrier device,

hot-electron diode, or hot carrier diode. Schottky diodes are widely used in radio frequency (RF)

applications.

When aluminum or platinum metal is joined with N-type semiconductor, a junction is formed between

the metal and N-type semiconductor. This junction is known as a metal-semiconductor junction or M-

S junction. A metal-semiconductor junction formed between a metal and n-type semiconductor creates

a barrier or depletion layer known as a schottky barrier.

The symbol of schottky diode is shown in the below figure. In schottky diode, the metal acts as

the anode and n-type semiconductor acts as the cathode.

How schottky diode works?

Unbiased schottky diode When the metal is joined with the n-type semiconductor, the conduction band electrons (free

electrons) in the n-type semiconductor will move from n-type semiconductor to metal to establish

an equilibrium state.

We know that when a neutral atom loses an electron it becomes a positive ion similarly when a

neutral atom gains an extra electron it becomes a negative ion.

The conduction band electrons or free electrons that are crossing the junction will provide extra

electrons to the atoms in the metal. As a result, the atoms at the metal junction gains extra electrons

and the atoms at the n-side junction lose electrons.

The atoms that lose electrons at the n-side junction will become positive ions whereas the atoms

that gain extra electrons at the metal junction will become negative ions. Thus, positive ions are

created the n-side junction and negative ions are created at the metal junction. These positive and

negative ions are nothing but the depletion region.

Since the metal has a sea of free electrons, the width over which these electrons move into the

metal is negligibly thin as compared to the width inside the n-type semiconductor. So the built-in-

potential or built-in-voltage is primarily present inside the n-type semiconductor. The built-in-

voltage is the barrier seen by the conduction band electrons of the n-type semiconductor when

trying to move into the metal.

To overcome this barrier, the free electrons need energy greater than the built-in-voltage. In

unbiased schottky diode, only a small number of electrons will flow from n-type semiconductor

to metal. The built-in-voltage prevents further electron flow from the semiconductor conduction

band into the metal.

The transfer of free electrons from the n-type semiconductor into metal results in energy band

bending near the contact.

Forward biased schottky diode

If the positive terminal of the battery is connected to the metal and the negative terminal of the

battery is connected to the n-type semiconductor, the schottky diode is said to be forward biased.

When a forward bias voltage is applied to the schottky diode, a large number of free electrons are

generated in the n-type semiconductor and metal. However, the free electrons in n-type

semiconductor and metal cannot cross the junction unless the applied voltage is greater than 0.2

volts.

If the applied voltage is greater than 0.2 volts, the free electron gains enough energy and

overcomes the built-in-voltage of the depletion region. As a result, electric current starts flowing

through the schottky diode.

If the applied voltage is continuously increased, the depletion region becomes very thin and finally

disappears.

Reverse bias schottky diode If the negative terminal of the battery is connected to the metal and the positive terminal of the

battery is connected to the n-type semiconductor, the schottky diode is said to be reverse biased.

When a reverse bias voltage is applied to the schottky diode, the depletion width increases. As a

result, the electric current stops flowing. However, a small leakage current flows due to the

thermally excited electrons in the metal.

If the reverse bias voltage is continuously increased, the electric current gradually increases due

to the weak barrier.

If the reverse bias voltage is largely increased, a sudden rise in electric current takes place. This

sudden rise in electric current causes depletion region to break down which may permanently

damage the device.

V-I characteristics of schottky diode

The V-I (Voltage-Current) characteristics of schottky diode is shown in the below figure. The

vertical line in the below figure represents the current flow in the schottky diode and the horizontal

line represents the voltage applied across the schottky diode.

The V-I characteristics of schottky diode is almost similar to the P-N junction diode. However,

the forward voltage drop of schottky diode is very low as compared to the P-N junction diode.

The forward voltage drop of schottky diode is 0.2 to 0.3 volts whereas the forward voltage drop

of silicon P-N junction diode is 0.6 to 0.7 volts.

If the forward bias voltage is greater than 0.2 or 0.3 volts, electric current starts flowing through

the schottky diode.

In schottky diode, the reverse saturation current occurs at a very low voltage as compared to the

silicon diode.

Advantages of Schottky Diode

Schottky diodes are used in many applications compare to other types of diodes that do not perform

well.

Low turn on voltage: The turn on voltage for the diode is between 0.2 and 0.3 volts. For a silicon

diode it is against 0.6 to 0.7 volts from a standard silicon diode.

Fast recovery time: A fast recovery time means a small amount of stored charge that can be used

for high speed switching applications.

Low junction capacitance: It occupies a very small area, after the result obtained from wire point

contact of the silicon. Since the capacitance levels are very small.

Applications of Schottky diode: 1. It is used in switching power supplies (SMPS).

2. As it generates less noise, it will use in sensitive communication receivers like radars.

3. It is used in clipping and clamping circuits and in computer gating.

4. It is used in construction of integrated circuits designed for high-speed digital logic

applications.