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Electronic Circuitsand Electronic
Devices
David A. Bell Electronic Circuits and Electronic Devices
Copyright Oxford University Press, 2010
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PREFACE
Thelaboratoryinvestigationsinthismanualaredesignedtodemonstratetheelectronicstechnology theory explained inmybook Electronic Circuits and Electronic Devices.Atotal of43laboratoryinvestigationsareofferedinvolvingtheconstructionandtestingofcircuitsdiscussedinthetextbook.Eachlaboratoryinvestigationconsistsof:
atitle anintroductionthatbrieflydescribestheinvestigation alistofrequiredequipmentandcomponents circuitdiagramsandconnectiondiagrams
step
by
step
procedures
to
be
followed
alaboratoryrecordsheetforrecordingdata ananalysissectionforprocessingthedata
Eachinvestigationcannormallybecompletedwithinatwohourperiod.Theprocedurescontain some references to the textbook;however,allnecessarycircuitand connectiondiagramsareprovidedinthemanual,sothattheinvestigationscanbeperformedwithoutthetextbook.
DavidBell
David A. Bell Electronic Circuits and Electronic Devices
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CONTENTS
1 Semiconductor Diode Characteristics 42 Diode Rectifier Circuits 93 Zener Diode .. 74 BJT Characteristics .. 195 BJT Bias Circuits 246 BJT Switching Circuits . 287 BJT Common Emitter Circuit . 338 BJT CC and CB Circuits . 379 JFET Characteristics ... 4210 JFET Bias Circuits ... 47
11 Basic JFET Circuits . 5212 CapacitorCoupled BJT Amplifier 57
13 DirectCoupled BJT Amplifier 6214 SCR Characteristics and 90 Phase Control 6715 SCR and TRIAC Control Circuits . 7216 UJT and PUT Circuits .. 7617 Photoconductive Cell, LED, and Solar Cell . 8218 Series Resistive Circuits 8719 Parallel Resistive Circuits 95
20 Seriesparallel Circuits. 100
21 Resistive Networks 104
22 Network Theorems 110
23 DC RCCircuit 11524 Oscilloscope 120
25 Rectifier Voltmeter 12526 AC RLCircuit. 12927 AC RCCircuit. 13328 Series & Parallel Impedance Circuits 137
29 Series Resonance 143
30 Parallel Resonance 147
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LABORATORY
INVESTIGATION 1SemiconductorDiode
Characteristics
Introduction
Theforward
characteristics
of
alow
current
switching
diode
and
amedium
current
recti
fierdiodeareinvestigated.Eachdeviceisforwardbiasedtogiveseveralcurrentlevels,andtheforwardvoltageismeasuredateachcurrent.ThisproducesatableofVF andIFquantitiesforplottingthecharacteristics.Diodereversecurrentisalsoinvestigated.
Equipment
DCpowersupply(050V,100mA)DCvoltmeter(50V)DCammeter(100mA)DCammeter(20 A)Lowcurrentswitchingdiode,e.g.,1N914
Rectifierdiode,
e.g.,
1N4005
Resistors(470 ,5W),(68k ,0.25W),(1k ,0.5W)Circuitboard
Procedure1 Low-CurrentDiode Characteristics
11 ConstructthecircuitshowninFig.11accordingtotheconnectiondiagraminFig.12.Notethatthelowcurrentdiode(D1)isconnectedtoterminalsAandBwithforwardbiasedpolarity.
100mA
Powersupply
1k AA
R
1
V D1
B
Figure 1-1 Circuit for determining low-current diode forward characteristics.
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Ammeter
Powersupply
AV
A COM
Voltmeter
VV
AR1 A COM
D1
BCircuitboard
Figure 1-2 Connection diagram for determining diode forward characteristics.
12 Adjustthepowersupplyvoltagecontrolforzerooutput.
13 SwitchonthepowersupplyandcarefullyadjustthevoltagetogivethecurrentlevelslistedforProcedure13onthelaboratoryrecordsheet.(Donotexceedadiodecurrentof20mA.)Ateachcurrentlevel,recordthediodeforwardvoltageontherecordsheet.
14 Adjustthepowersupplytoreturnthediodevoltagetozero.Switchoff;thenusingthe20 Arangeammeter,reconstructthecircuitasshowninFig.13.Notethatthediode
polarity
is
reversed,
the
ammeter
is
connected
directly
in
series
with
the
diode,andR1 isa68k resistor.20 A
Powersupply
68kA A
R1
V D1
B
Figure 1-3 Circuit diagram for determining diode reverse characteristics.
15 Switchonthepowersupplyandadjustthedevice(reverse)voltageto30V.Recordthediodereversecurrentonthelaboratoryrecordsheet.
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Procedure2 RectifierDiode Characteristics
21 Resetthepowersupplyoutputtozeroandremovethelowcurrentdiodefromthecircuit.
22 ReconstructthecircuitasillustratedinFig.14,andconnecttherectifierdiode(D2)withforwardbiasedpolaritytoterminalsAandB.NotethatR1 isnow470 andthatthevoltmeterisconnecteddirectlyinparallelwithD2.
100mA
Powersupply
470 AA
R1
V D2
B
Figure 1-4 Circuit for determining rectifier diode forward characteristics.
23 Switch on the power supply and adjust the diode voltage in steps as listed forProcedure23onthelaboratoryrecordsheet.(Donotexceedadiodecurrentof60mA.)At each voltage step, record thediode forward current on the laboratory recordsheet.
24 SwitchoffthepowersupplyandrearrangethecircuitasinFig.13,usingtherectifierdiodeanda20 Aammeter.
25 Switchonthepowersupplyandadjustthedevice(reverse)voltageto30V.Record
the
reverse
current
on
the
laboratory
record
sheet.
Analysis
1 Plot the forwardcharacteristicof the lowcurrentdiode (D1) from the resultsofProcedure1.
2 Plot the forward characteristic of the rectifier diode (D2) from the results ofProcedure2.
3 Fromtheforwardcharacteristics,determinetheapproximateforwardvoltagedropanddc forwardresistance forD1 andforD2.Estimate theac resistance foreachdiode.
4Comment
on
the
results
of
Procedures
1
5
and
2
5
(reverse
biased
diode
current
measurements).
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RecordSheetL1-1
RecordSheetLab.#1 Semiconductor Diode Characteristics
Date
Procedure 1-3
Low-Current Diode Forward Characteristics
IF(mA)
VF (V)
0.1 1 2 3 5 10 15 20
Procedure 1-5
Reverse BiasVR IR
30 V
Procedure2-3
Rectifier Diode Forward Characteristics
IF(mA)
VF (V)
0.5 1 5 10 20 30 40 50 60
Procedure2-5
Reverse BiasVR IR
30 V
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RecordSheetL1-2
Low-Current Diode Forward Characteristics
(mA)
20
15
IF10
5
00 0.1 0.2 0.3 0.4
VF
0.5 0.6 0.7 0.8(V)
Rectifier Diode Forward Characteristics
(mA)
60
50
40
IF30
20
10
00 0.1 0.2 0.3 0.4
VF
0.5 0.6 0.7 0.8(V)
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LABORATORY
INVESTIGATION 2Diode Rectifier Circuits
Introduction
Ahalfwaverectifiercircuitisconstructed,anditsinputandoutputwaveformsareinvestigated.Thenafullwavebridgerectifiercircuitisconstructedandtested.Finally,atwodiodefullwaverectifiercircuitusingacentretappedtransformerisconstructed,anditsoutputwaveformsareinvestigated.
Equipment
115V,60Hzvariablevoltagetransformer(variac)115V,60Hz,1:1isolatingtransformer115V,60Hz,transformerwithcentretappedsecondaryOscilloscopeLowcurrentdiodes(4 1N914)Resistor(100 ,0.5W)Circuitboard
Procedure1 Half-WaveRectification
11 ConstructthehalfwaverectifiercircuitshowninFig.21accordingtotheconnectiondiagraminFig.22.(ThisistherectifiercircuitinFig.31ainthetextbook.)
115V
60Hz
VariacIsolatingtransformer
D1
RL
100
Vi
Vo
Tooscilloscope
Figure 2-1 Half-wave rectifier test circuit.
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Oscilloscope
VariacIsolatingtransformer
Circuitboard
D1
RL
Figure 2-2 Connection diagram for the half-wave rectifier test circuit.
12 Adjustthevariacforthelowestoutputvoltage;thenconnectthe115V,acsupply.
13 Switchontheacsupplyandslowlyincreasethevariacoutputuntilthediodecircuitinputwaveform(attheisolatingtransformeroutput)measures10Vpeaktopeakasdisplayedontheoscilloscope.
14 Measurethepeaklevelofthediodecircuitoutputvoltage.Neatlysketchthecircuit
inputand
output
waveforms
on
the
laboratory
record
sheet
and
record
the
measured
peaklevels(ViandVo).
15 Increasethediodecircuitinputto20VpeaktopeakandrepeatProcedure14.
16 Switchofftheacsupplyandreversethediodeterminals.
17 SwitchontheacsupplyandrepeatProcedure14withVi 10Vpeaktopeak.
Procedure2 Full-Wave Bridge Rectifier
21 Construct the fullwave rectifiercircuit shown inFigs. 23 and24. (This rectifiercircuitisthesameasinFig.36inthetextbook.)
22Repeat
Procedures
1
2
through
1
5.
23 Switch off the ac supply, and then disconnect (opencircuit) one terminal of onediode.
24 Switchontheacsupply,andnotetheopencircuiteffectontheoutput.
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Vi
115V60Hz
Isolating
Variac
transformer
D1 D3Vo
RL100
Tooscilloscope
D2 D4
Figure 2-3 Bridge rectifier circuit.
Tooscilloscope
Isolatingtransformer
Circuitboard
Tooscilloscope
Fromvariac
D1 D3
RLD2 D4
Figure 2-4 Connection diagram for the bridge rectifier circuit.
Procedure3 Two-Diode Full-Wave Rectifier
31 ConstructthefullwaverectifiercircuitshowninFig.25accordingtotheconnectiondiagraminFig.26.(ThisrectifiercircuitisthesameasinFig.33inthetextbook.)
32 RepeatProcedures12through15.
115V60Hz
Variac
Transformerwithcentre
tappedsecondary
D1 RL
100
D2
Vi
Vo To
oscilloscope
Figure 2-5 Two-diode full-wave rectifier circuit.
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Fromvariac
Transformerwith
centretapped
secondary
Tooscilloscope
Circuitboard
D1
Tooscilloscope
RL
D2
Figure 2-6 Connection diagram for the two-diode full-wave rectifier circuit.
Analysis
1 DiscusstheresultsofProcedure1.Explainthedifferencebetweentheinputandoutputwaveforms.
2 DiscusstheresultsofProcedure2.Explaintheeffectofopencircuitingonediode.3 DiscusstheresultsofProcedure3.Comparethetwodiodefullwaverectifiertothebridgerectifier.Whataretheadvantagesanddisadvantagesofeachcircuit?
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RecordSheetL2-1
RecordSheetLab.# 2 DiodeRectifier Circuits
Date
Half-WaveRectifier Circuit
Procedure 1-4
Input voltage. Vi = 10Vp-to-p
Output voltage. Vo =
Procedure 1-5
Input voltage. Vi = 20 Vp-to-p
Output voltage. Vo =
Procedure 1-7
Input voltage. Vi = 10Vp-to-p
Output voltage. Vo =
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RecordSheetL2-2
RecordSheet 2Lab.#2
Full-Wave Bridge Rectifier Circuit
Procedure2-2
Input voltage. Vi = 10Vp-to-p
Output voltage. Vo =
Input voltage. Vi = 20 Vp-to-p
Output voltage. Vo =
Date
Procedure2-4
Procedure3-2
Input voltage. Vi = 10Vp-to-p
Output voltage. Vo =
Input voltage. Vi = 20 Vp-to-p
Output voltage. Vo =
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LABORATORY
INVESTIGATION 3
ZenerDiode
Introduction
ThereversecharacteristicsofaZenerdiodeare firstinvestigated.Thedevice is reversebiasedinstepvoltagelevels,andthereversecurrentismeasuredateachstepuntilreversebreakdown occurs.After thebreakdown voltage is reached, the reverse current is increasedinstepsandthediodevoltageismeasuredateachstep.InthiswayatableofVRandIRquantitiesisobtainedforplottingthereversecharacteristics.(Zenerdiodeforwardcharacteristicscanbeinvestigatedinthesamewayasforanordinarylowcurrentdiode.)AsimpleZenerdioderegulatorcircuitisconstructedandtestedusingahalfwaverectifier
powersupply
as
an
input.
Equipment
DCpowersupply(050V,100mA)OscilloscopeDCAmmeter(050mA)Multirangedcvoltmeter(020V)4digit(orbetter)digitalvoltmeter115V,60Hzvariablevoltagetransformer(variac)115V,60Hz,1:1isolatingtransformer
Zenerdiode1N753
Lowcurrentdiode1N9141Wresistors120 ,150Capacitor(330 F,25V)Circuitboard
Procedure1 1N753 Characteristics
11 Connect the circuit and test equipment as shown in Fig. 41a according to theconnection diagram in Fig. 41b. Note that the Zener diode is connected withreversebiaspolarity.
12 Adjustthepowersupplyforzerooutput;thenconnectitsacsupplyandswitchon.
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Power
supply
150kA
R1
V
D1
1N753
Ammeter
Voltmeter(a)Circuit
PowersupplyA
VA COM
VV
A
CircuitR1 A COM
board D1
B
(b)Connection
diagram
Figure 4-1 Determination of Zener diode characteristics.
13 CarefullyincreasethediodereversevoltageinstepsaslistedforProcedure13onthe laboratory record sheetuntil thediodegoes into reversebreakdown.Ateachvoltagestep,recordthediodereversecurrentontherecordsheet.
14 When thediodebreakdownvoltage isreached,carefullyadjustthepowersupplyvoltagetosetthediodecurrenttothestepslistedforProcedure14onthelaboratoryrecordsheet.Ateachcurrentstep,recordthemeasuredreversevoltage.
Procedure2 Zener DiodeRegulator
21 Construct the halfwave rectifier power supply and Zener regulator shown inFig.42, togetherwith the test equipment. (This is the regulator circuitdesignedinExample317inthetextbookandanalyzedinExample318.)
22 Adjustthevariacforzerooutput;thenconnectthe115Vacsupply.
23 Switchontheacsupplyandslowlyincreasethevariacoutputtogivea16Vdcinput(Vi(dc))totheregulator.MeasureandrecordtheregulatoroutputvoltageattheZenerdiodeterminals.
24 Usingtheoscilloscope,measuretheregulatorpeaktopeakinputripplevoltage(Vri)andthepeaktopeakoutputripplevoltage(Vro).
2
5
Adjust
the
ac
input
voltage
to
increase
Vi(dc)by
10%.
Measure
and
record
the
dc
out
putvoltagechange(theregulatorsourceeffect), Vo(source).
26 ResetthevariactosettheregulatorinputbacktoVi(dc) 16V.
27 DisconnectoneendofRL andobservetheoutputvoltagechangefromfullloadtonoload(theregulatorloadeffect), Vo(load ).Record Vo(load ).
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C
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115V
60Hz
VariacIsolatingtransformer
D11N914
C1330 F V Vi(dc)
R1
150
D21N753
RL
120
Vri
Vro
V
Tooscilloscope
(a)Circuit
Voltmeter
VV
A COM
Tooscilloscope
R1D1
1 D2
4digitvoltmeter
VV
A COM
RL
Variac Isolatingtransformer Circuitboard
(b)Connectiondiagram
Figure 4-2 Zener diode regulator test circuit.
Analysis1 FromtheresultsofProcedures13and14,plotagraphshowingtheZenerdiodereversecharacteristics.
2 From theZenerdiode reverse characteristics,determine the reversevoltage atIZ 20mA.Calculatethedynamicimpedanceforthedevice.
3 Calculate the line regulation, load regulation,and ripple reduction factorproducedby theZenerdioderegulator.Compare theresults to thosecalculated inExample318inthetextbook.
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RecordSheetL4-1
RecordSheetLab.#4 ZenerDiode
Date
Zener DiodeReverseCharacteristics
Procedure 1-3VR(V) 2
IR(mA)
4 6 6.05 6.1 6.2
Procedure 1-4VR(V)
IR(mA) 5 10 20 30 40
Zener DiodeRegulator
Procedure2-3 Output Voltage Vo = VZ =
Procedure2-4 Peak-to-peakripple Voltage:
Vri = Vro =
Procedure2-5 Source effect Vo(source)=
Procedure2-7 Load effect Vo(load) =
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LABORATORY
INVESTIGATION 4
BJT Characteristics
Introduction
Thecommonemitter(CE)andcommonbase(CB)outputcharacteristicsaredeterminedforaBJTbythepointbypointprocess.ThetransistorisfirstconnectedinCEconfigurationanditsbasecurrent(IB)issetataparticularlevel.Thecollectoremittervoltage(VCE)invariedinsteps,andthecollectorcurrent(IC)isnotedateachVCE step.ThisgivesatableofICversusVCE levelsfromwhichtheCEoutputcharacteristiccanbeplotted.TheprocessisrepeatedforseveralIB levelstogiveafamilyofCEcharacteristics. TheBJTcommonbase(CB)outputcharacteristicsaredeterminedinasimilarway,andtheCEandCBcurrent
gaincharacteristics
are
derived
from
the
output
characteristics.
Equipment
2dcpowersupplies(0to20V)DCvoltmeter(0to25V)DCammeter(0to100 A)2dcammeters(0to10mA)Resistors(2.2k ,0.5W),(100k ,0.25W)LowcurrentgeneralpurposenpnBJT(e.g.,2N3904)Circuitboard
Procedure1 Common Emitter Output Characteristics
11 ConnectthecircuitandtestequipmentasshowninFig.71aaccordingtotheconnectiondiagraminFig.71b.(Notethatthebasecurrentammeteristomeasureinmicroamps.)
12 Setbothpowersuppliesforzerooutput,andthenswitchon.
13 SetVCE to15V,andthenincreasethebasebiasvoltagetogiveIB 10 A.
14 ReadtheIC levelandrecorditonthelaboratoryrecordsheet.
15 MaintainingIB constant,adjustVCE toeachofthevoltageslistedforProcedure1on
thelaboratory
record
sheet.
Record
the
measured
IC at
each
VCE level.
(At
each
IC
measurement,carefullycheckandadjustIB ifnecessary.)
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IC
AIB
R1
APower
Powersupply
100k VA supply
(a)CEtestcircuit
Ammeter(IB) Ammeter(IC) Voltmeter(VCE)
VA
VA COM
AVA COM
VA COM
Powersupply
R1 CBEQ1
Powersupply
Circuitboard
(b)Connectiondiagram
Figure 7-1 Circuit and connection diagram for determining BJ T CE characteristics.
16 ReadjustVCE to15VandsetIB to20 A.ReadtheIC levelandrecorditonthelaboratoryrecordsheet.
17 RepeatProcedure15.
18 ReadjustVCE to15VandsetIB to30 A.ReadtheIC levelandrecorditonthelabo
ratory
record
sheet.
19 RepeatProcedure15.
110 ReadjustVCE to15Vandset IB to40 A.Read the IC levelandrecord iton thelaboratoryrecordsheet.
111 RepeatProcedure15.
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Procedure2 Common Base Output Characteristics
21 Set thepowersupplyvoltages tozero,switchoff,and thenmodify thecircuitasshowninFig.72.
IE ICR1
Powersupply
A2.2k A
PowerV supply
(a)CBtestcircuit
Ammeter(IE) Ammeter(IC) Voltmeter(VCE)
VA
VA COM
AV
A COM
VA COM
R1CBEQ1
Power
supply
Power
supply
Circuitboard
(b)Connectiondiagram
Figure 7-2 Circuit and connection diagram for determining BJ T CB characteristics.
22 Withbothpowersuppliessettozero,switchon.
23 AdjustVCB to15V;thenincreasethebasebiasvoltagetoproducea1mAemittercurrent(IE).
24Read
the
IC level
and
record
it
on
the
laboratory
record
sheet.
25 MaintainingIE constant,adjustVCB toeachofvoltageslistedforProcedure2onthelaboratoryrecordsheet.RecordthemeasuredIC ateachVCB level.(AteachICmeasurement,carefullycheckandadjustIE ifnecessary.)
26 ReadjustVCB to15VandsetIE to3mA.ReadtheIC levelandrecorditonthelaboratoryrecordsheet.
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27 RepeatProcedure25.
28 ReadjustVCB to15VandsetIE to5mA.ReadtheIC levelandrecorditonthelabo ratoryrecordsheet.
29Repeat
Procedure
25.
Analysis
1 PlottheBJTCEcharacteristicsfromtheresultsofProcedure1.2 DrawaverticallineontheCEcharacteristicsatVCE 5V.Fromtheintersectionsofthislinewiththedevicecharacteristics,prepareatableofcorrespondingIC andIB levels.Seethelaboratoryrecordsheet.
3 CalculatethehFEvaluesforeachIC levelintheVCE 5VcolumnintheIC/IBtable,andrecordtheseinthetable.
4Plot
the
BJT
CE
current
gain
characteristics
from
the
IC/IBtable.
5 PlottheBJTCBcharacteristicsfromtheresultsofProcedure2.6 DrawaverticallineontheCBcharacteristicsatVCB 5V.Fromtheintersectionsofthislinewiththedevicecharacteristics, prepareatableofcorrespondingICandIElevels.Seethelaboratoryrecordsheet.
7 CalculatethehFBvaluesforeachIC levelintheIC/IEtable.8 PlottheBJTCBcurrentgaincharacteristicsfromtheIC/IEtable.
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RecordSheetL7-1
RecordSheetLab.# 7 BJTCharacteristics
Date
Procedure 1 Common-Emitter Characteristics
(IB= 10 A)
(IB= 20 A)
(IB= 30 A)
(IB= 40 A)
VCE(V)
IC(mA)
IC(mA)
IC(mA)
IC(mA)
0.5 1 2 5 10 15
Fromthe CE Characteristics
(VCE = 5 V) IB(A) 10
IC(mA)
hFE
20 30 40
Procedure2 Common-Base Characteristics
(IE = 1 mA)
(IE= 3 mA)
(IE= 5 mA)
VCB(V)
IC(mA)
IC(mA)
IC(mA)
0.5 1 2 5 10 15
Fromthe CB Characteristics
(VCB = 5 V) IE(mA) 1 3 5
IC(mA)
hFB
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LABORATORY
INVESTIGATION 5
BJT Bias Circuits
Introduction
ThreebasicBJTbiascircuitsareinvestigated:basebias,collectortobasebias,andvoltagedividerbias.TwotransistorswithdifferenthFEvalues(hFE(A)andhFE(B))areusedtodemonstratethedccurrentgaineffectoneachbiascircuit.Eachcircuitisconstructed,andthedcvoltagesthroughoutthecircuitaremeasuredfortheBJTwithhFE(A) andthenfortheBJTwithhFE(B).Theresultsarecomparedwithcircuitsinthetextbook.
Equipment
DCpower
supply(0
to
20
V)
DCvoltmeter(0to20V)0.25Wresistors470k,270k,33k,12k,2.2k,1.2k,1k2differenttypeoflowcurrentnpnBJTs(e.g.,2N3904and2N718)Circuitboard
Procedure1 Base Bias and hFE Values
11 IdentifythetwotransistorsasAandB.
12 UsingtransistorA,connect thebasebiascircuitand testequipmentasshown inFig.91.
13Switch
on
the
power
supply
and
adjust
its
output
to
give
VCC 18
V.
14 MeasureVCE. IftransistorQ1 issaturated,increasethebaseresistorasnecessarytomoveQ1outofthesaturatedstate.Onthelaboratoryrecordsheet,recordVCEandtheresistanceofRB forthebasebiascircuitwithtransistorA.
15 Switchoffthepowersupply,andsubstitutetransistorBfortransistorA.
16 SwitchthepowersupplyonandagainandcheckthatVCC 18V.
17 MeasureVCE andagain increaseRB ifnecessary tomove the transistoroutof thesaturatedstate.RecordVCE andtheresistanceofRB forthebasebiascircuitwithtransistorBonthelaboratoryrecordsheet.
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Powersupply
VCC
18V
VoltmeterCircuitboard
RCRB470k RC2.2k V RB
VA COM
Q1
CB Q1E
(a)Basebiastestcircuit (b)Connectiondiagram
Figure 9-1 Base bias test circuit and connection diagram.
Procedure2 Collector-to-BaseBias
21 UsingtransistorA,connectthecollectortobasebiascircuitandtestequipmentasshowninFig.92.
Powersupply
VCC
18V
RC
VoltmeterCircuitboard
RC
RB270k
2.2kQ1
V
VA COM
RB
CB Q1E
(a)Collectortobasebiastestcircuit (b)Connectiondiagram
Figure 9-2 Collector-to-basebias test circuit and connection diagram.
22 SwitchonthepowersupplyandadjustitsoutputtogiveVCC 18V.
23Measure
VCE,
and
on
the
laboratory
record
sheet,
note
the
measured
voltage
for
collectortobasebiaswithtransistorA.
24 Switchoffthepowersupply,andsubstitutetransistorBfortransistorA.
25 SwitchthepowersupplyonandagaincheckthatVCC 18V.
26 MeasureVCE againandrecordthemeasuredvoltageforcollectortobasebiaswithtransistorB.
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Procedure3 Voltage DividerBias
31 UsingtransistorA,connect thevoltagedividerbiascircuitand testequipmentasshowninFig.93.
R1 RC
VCC
18V VoltmeterCircuitboard
Powersupply
33k
R212k
1.2kQ1
RE1k
V
VA COM
R1 RC
CB Q1E
R2 RE
(a)Voltagedividerbiastestcircuit (b)Connectiondiagram
Figure 9-3 Voltage divider bias test circuit and connection diagram.
32 SwitchonthepowersupplyandadjustitsoutputtogiveVCC 18V.
33 MeasureVC andVE andnotethemeasuredvoltagesforvoltagedividerbiaswithtransistorAonthelaboratoryrecordsheet.
34 Switchoffthepowersupply,andsubstitutetransistorBfortransistorA.
35 SwitchthepowersupplyonandonceagaincheckthatVCC 18V.
36 MeasureVC andVE againandnotethemeasuredvoltagesforvoltagedividerbiaswithtransistorBonthelaboratoryrecordsheet.
Analysis
1 FromtheresultsofProcedure1calculatehFE(A)andhFE(B).2 OnthelaboratoryrecordsheettabulatethemaximumandminimumVCE levelsforeachbiascircuitfortransistorsAandB.UsethemeasuredvoltagestocalculateIC
for
each
circuit.
Record
the
IC levels
in
the
table
on
the
laboratory
record
sheet.
3 Drawadcloadlineandmarkthebiaspointextremesforeachbiascircuit.4 ComparethecircuitstabilityforeachbiascircuittothesimilarcircuitsinSection55inthetextbook.
5 UsingthemeasuredhFEvalues,analyzeeachcircuittocalculateICandVCE.Comparethecalculatedandmeasuredquantities.
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RecordSheetL9-1
RecordSheetLab.#9 BJTBias Circuits
Date
Procedure 1
Transistor A
Transistor B
VCE RB IB IC hFE
Procedure2
Transistor ATransistor B
VCE RB IB IC
Procedure 3
Transistor A
Transistor B
VC VE VCE IC
Analysis
VCE(min)
VCE(max)
IC(min)
IC(max)
Basebias Collector-to-base
bias
Voltage divider
bias
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LABORATORY
INVESTIGATION 6BJT Switching Circuits
Introduction
AdirectcoupledBJTswitchingcircuit isconstructedand testedwithdc inputvoltagesandwithasquarewaveinput.Twocapacitorcoupledswitchingcircuitsarealsotested:onewiththeBJTbiasedinanormallyonstate,andtheotherwiththeBJTnormallyoff.
Equipment
OscilloscopeSquarewavegenerator2dcpowersupplies(0to20V)DCvoltmeter(0to20V)Resistors(4.7k ,0.25W),(8.2k ,0.25W),(27k ,0.25W),(39k ,0.25W)Capacitors(0.22 F,25V)LowcurrentgeneralpurposenpnBJT(e.g.,2N3904)Circuitboard
Procedure1 Direct-Coupled Switching Circuit
11 ConstructthedirectcoupledBJTswitchingcircuit inFig.101. (This isthecircuitdesignedinExample522inthetextbook.)
VCC
12V Powersupply
CircuitboardPowersupply
RB
27k
RC8.2k
Q1
RC
RB CB Q1E
(a)Directcoupledswitchingcircuit (b)Connectiondiagram
Figure 10-1 Direct-coupled BJ T switching circuit.
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12 SwitchonthecollectorpowersupplyandadjustVCC to12V.
13 SwitchonthebasepowersupplyandadjustVB to0V.
14 MeasureandrecordVCE.
15 AdjustVB to5VandagainmeasureandrecordVCE.
16 SubstitutethesignalgeneratorforthebasesupplyvoltageasinFig.102,andconnecttheoscilloscope(using10:1probes)tomonitorthewaveforms.
VCC
12V
Tooscilloscope
Powersupply
Tooscilloscope
RB
RC8.2k
Q1
SignalgeneratorRC
CQ
B 1
27kE
(a)Directcoupledcircuit
Circuitboard
(b)Connectiondiagram
Figure 10-2 Waveform investigation for a direct-coupled BJ T switching circuit.
17 Setthesignalgeneratoroutputfora;3V,10kHzsquarewave.
18 Sketchthecircuitinputandoutputwaveformsonthelaboratoryrecordsheet,andnotetheupperandlowerpeakvoltages.
19Increase
the
signal
frequency
to
investigate
the
circuit
switching
times.
110 Measureandrecordtheturnontime(ton)andtheturnofftime(toff),andsketchthewaveformsontherecordsheet.
Procedure2 Normally-On Capacitor-CoupledSwitching Circuit
21 ConstructthenormallyoncapacitorcoupledBJTswitchingcircuitinFig.103.(Thiscircuit is designed inExample 523 in the textbook.)Leave the signal generatorunconnectedatthistime.
22 SwitchonthecollectorpowersupplyandadjustVCC to9V.
23Measure
VCE and
note
the
voltage
on
the
record
sheet.
24 ShortcircuitthetransistorbaseandemitterterminalsandagainmeasureandrecordVCE.Removetheshortcircuit.
25 Connectthesignalgeneratorandadjustthesignaltoa;3V,10kHzsquarewave.
26 Sketchthecircuitinputandoutputwaveformsonthelaboratoryrecordsheet,andnotetheupperandlowerpeakvoltages.
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RB39k
VCC
9V
RC
Tooscilloscope
Powersupply
Tooscilloscope
4.7kSignalgenerator
RBRC
C1
Q1
0.22 F
CB Q1E
C1
(a)Normallyoncircuit
Circuitboard
(b)Connectiondiagram
Figure 10-3 Normally-on capacitor-coupled BJ T switching circuit.
Procedure3 Normally-OffCapacitor-CoupledSwitching Circuit
31 Switchoffthepowersupply,andreconstructthecircuitintothenormallyoffcapacitorcoupledswitchingcircuitinFig.104.
To RC
VCC
9V
Tooscilloscope
Powersupply
oscilloscope 4.7kC1
Q10.22 F
SignalgeneratorRC
CQ
RB39k B 1C1 RB
(a)Normallyoffcircuit
Circuitboard
(b)Connectiondiagram
Figure 10-4 Normally-off capacitor-coupled BJ T switching circuit.
32 SwitchonthepowersupplyandsetVCC to9V.
33 MeasureVCE andnotethevoltageontherecordsheet.
34 Connectthesignalgeneratorandadjustthesignaltoa;3V,10kHzsquarewave.
35 Sketchthecircuitinputandoutputwaveformsonthelaboratoryrecordsheet,andnotetheupperandlowerpeakvoltages.
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Analysis
1 Discuss themeasuredvoltagesandwaveforms for thedirectcoupled switching
circuit.2 Analyze thedirectcoupledcircuit todetermine IC,IB,andhFE(min).Calculate the
minimumbaseinputvoltagetodrivethetransistorintosaturation.3 Discussthecircuitswitchingtimes.4 Discussthemeasuredvoltagesandwaveformsforthenormallyoncapacitorcoupledswitchingcircuit.
5 AnalyzethenormallyoncapacitorcoupledcircuittodetermineIC,IB,andhFE(min).Calculatetheminimumbaseinputvoltagetodrivethetransistorintocutoff.
6 Discussthemeasuredvoltagesandwaveformsforthenormallyoffcapacitorcoupledswitchingcircuit.
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RecordSheetL10-1
RecordSheetLab.# 10 BJTSwitching Circuits
Date
Procedure 1-4
Procedure 1-5
Procedure 1-8
+Vo(pk) =Vo(pk) =
(Vi = O)
(Vi= 5 V)
VCE =
VCE =
Input
waveform
Output
waveform
Procedure 1-10
ton=toff=
Input
waveform
Output
waveform
Procedure2-3
Procedure2-4
Procedure2-6
+Vo(pk) =Vo(pk) =
(Vi = O)
VCE =
VCE =
Input
waveform
Output
waveform
Procedure3-3
Procedure3-5
+Vo(pk) =Vo(pk) =
VCE =
Input
waveform
Output
waveform
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LABORATORY
INVESTIGATION 7BJT Common EmitterCircuit
Introduction
ABJT commonemitter circuit is constructed and tested for dc and ac performance.Circuitmaximumacoutputvoltageisinvestigatedtogetherwithacvoltagegain,inputimpedance,andoutputimpedance.Thecircuitisthenmodifiedtohaveanunbypassedemitterresistor,andtheacperformanceisagaininvestigated.
Equipment
DCpowersupply(0to20V)DCvoltmeter(0to20V)OscilloscopeSignalgenerator0.25Wresistors3.9k,4.7k,56k,68k,82k15Vcapacitors0.12 F,10 F,180 FLowcurrentgeneralpurposenpnBJT(e.g.,2N3904)
Circuitboard
Procedure1 DC and AC Conditions
11 ConstructthecircuitinFig.111.(ThisisthecircuitinFig.624inthetextbook.)Leavethesignalgeneratorandoscilloscopeunconnectedatthistime.
12 SwitchonthepowersupplyandadjustitsoutputforVCC 12V.
13 MeasureandrecordthelevelsofVB,VE,andVC.
14 ConnectthesignalgeneratorandoscilloscopetothecircuitasillustratedinFig.111b.
15 Setthesignalgeneratortoproducea3kHzsinewaveandadjustthesignalamplitudetogivemaximumundistortedoutputfromthecircuit.(Notethatitmaybenecessary
touse
avoltage
dividertypically
a100
k and
a100
resistorto
reduce
the
signalamplitude.)
16 Sketch the input and outputwaveforms, and record the peak input and outputvoltages.
17 Adjustthesignalamplitudetoproducea;1Voutput.RecordthepeaklevelsofViandVo andcalculatethecircuitvoltagegain.
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R168k RC3.9k
VCC
12V
C3
C1
10 F
vs R256k
Q1
RE4.7k
0.12 F
C2180 F
RL82k Tooscilloscope
R1
Tooscilloscope
RCC3
(a)Commonemittertestcircuit
Signalgenerator
C1
R2 RE
PowersupplyCB QE
C2 RL
Circuitboard
(b)Connectiondiagram
Figure 11-1 Common-emitter circuit and test equipment.
Procedure2 Input and Output Impedances
21 SetthesignalgeneratorasinProcedure17.
22 Temporarilydisconnect thesignalgeneratorandconnecta1.8k resistor (Ra) inserieswiththesignalgeneratorandthecircuitinput,asillustratedinFig.112.
Ra
1kvs
R168kC1
R256k
Tooscilloscope
R1
C1
Tooscilloscope
RCC3
Powersupply
(a)Circuitmodification
Signalgenerator
Ra
R2 RE
CB Q1E
C2 RL
Circuitboard
(b)Connectiondiagrammodification
Figure 11-2 Common-emitter circuit input resistance measurement.
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23 CheckthatthesignalvoltageamplitudeappliedtoRa isthesameasthatmeasuredinProcedure17.
24 Observe theamplitudeof thecircuitacoutputvoltage.Change the resistanceof
Ra asnecessary
to
give
an
output
amplitude
which
is
half
of
that
measured
in
Procedure15.RecordtheresistanceofRa asthecircuitinputimpedance(Zi).
25 Disconnect Ra, reconnect the signal generator, and adjust the signal level to thatmeasuredinProcedure17onceagain.
26 Temporarilydisconnectthe82k loadresistor(RL)andsubstitutea3.9k resistor(Rb)forRL.
27 Observe theamplitudeof thecircuitacoutputvoltage.Change the resistanceofRb as necessary togive anoutput amplitudewhich ishalfof thatmeasured inProcedure16.RecordtheresistanceofRb asthecircuitoutputimpedance(Zo).
Procedure3 UnbypassedEmitter Resistor31 DisconnectRbandreconnectRL.
32 Disconnecttheemitterbypasscapacitor;thenrepeatProcedure17.
33 RepeatProcedures21through27startingwithanewresistanceofRa 27k andusingRb 3.9k ,asbefore.
Analysis
1 FromtheresultsofProcedure1,plotthedcandacloadlinesfortheCEcircuitandshowthemaximumoutputvoltageswing.
2Analyze
the
circuit
to
determine
the
dc
voltages
and
compare
to
the
measured
voltages.3 Analyze the circuit todetermineAv,and compare to theAv from the resultsofProcedure17.Commentonthephaserelationshipbetweentheinputandoutputwaveforms.
4 AnalyzethecommonemittercircuittoestimateZiandZo.ComparethecalculatedvaluestothosemeasuredinProcedure2.
5 FromtheresultsofProcedure33,calculatethevoltagegain(Av)forthecommonemittercircuitwithanunbypassedemitterresistor.AnalyzethecircuittodetermineAvandcomparetothemeasuredAv.
6 AnalyzethecommonemittercircuitwithanunbypassedemitterresistortoestimateZiandZ
o
.ComparethecalculatedvaluestothosemeasuredinProcedure33.
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RecordSheetL11-1
RecordSheetLab.#11 BJTCommon-Emitter Circuit
Date
Procedure 1-3 VCC VB VE VC
Procedure 1-6Input
wavefor
m
Output
wavefor
m
Procedure 1-7 Vi(pk) = Vo(pk) = Av =
Procedure2-4 Zi =
Procedure2-7 Zo =
Procedure3-2 Vi(pk) = Vo(pk) = Av =
Procedure3-3 Zi = Zo =
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LABORATORY
INVESTIGATION 8
BJT CC and CB Circuits
Introduction
BJTcommoncollectorandcommonbasecircuitsareconstructedandtestedfordcandacperformance.Voltagegain,inputimpedance,andoutputimpedanceareinvestigatedforbothcircuits.
Equipment
DCpowersupply(0to20V)DCvoltmeter(0to20V)OscilloscopeSignalgenerator0.25Wresistors(56 ,1k ,1.2k ,3.9k ,4.7k ,27k ,56k ,68k ,82k )15Vcapacitors(0.12 F,10 F,180 F)LowcurrentgeneralpurposenpnBJT(e.g.,2N3904)Circuitboard
Procedure1 Common-CollectorCircuit (EmitterFollower)
11 ConstructthecircuitinFig.121.Leavethesignalgeneratorandoscilloscopeunconnectedatthistime.
12 SwitchonthepowersupplyandadjustitsoutputforVCC 12V.
13 MeasureVB,VE,andVC,andrecordthevoltagesonthelaboratoryrecordsheet.
14 ConnectthesignalgeneratorandoscilloscopetothecircuitasillustratedinFig.121.
15 Setthesignalgeneratorfrequencyto3kHzandadjustthesignalamplitudetogivea;0.5Voutput.
16 Sketchtheinputandoutputwaveformsonthelaboratoryrecordsheet,andrecordthepeakinputandoutputvoltagelevels.
17Temporarily
disconnect
the
signal
generator
and
connect
a27
k resistor
(Ra)
in
serieswiththesignalgeneratorandthecircuitinput.
18 CheckthattheacsignalvoltagetoRa isthesameasthecircuitinputvoltagemeasuredinProcedure16.
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R168k
VCC
12V
C1
Q110 F C2
Powersupply
vR2
s 56kRE
4.7k 180 F RL1kTooscilloscope
R1
(a)Commoncollectortestcircuit
Signalgenerator
C1
R2 RE
CB Q ToE
oscilloscope
C2 RL
Circuitboard
(b)Connectiondiagram
Figure 12-1 BJ T Common-collector circuit and test equipment.
19 Observetheamplitudeofthecircuitacoutputvoltage.ChangetheresistanceofRaasnecessarytogiveanoutputamplitudewhichishalfofthatmeasuredinProcedure16.RecordtheresistanceofRaasthecircuitinputimpedance(Zi).
110 DisconnectRa,reconnect thesignalgenerator,andagainadjust thesignal level tothat
measured
in
Procedure
16.
111 Temporarilyconnecta56 resistor(Rb)inparallelwithRL;thenreadjusttheinputamplitudetogivethemaximumundistortedoutput.
112 DisconnectandreconnectRb toseeifitspresencereducestheoutputamplitudebyafactorof2.ChangeRb asnecessary togivethiseffect.RecordtheresistanceofRbasthecircuitoutputimpedance(Zo).
Procedure2 Common-Base Circuit
21 ConvertthecommoncollectorcircuitintoacommonbasecircuitbythemodificationsshowninFig.122.Leavethesignalgeneratorandoscilloscopeunconnectedatthis
time.(The
circuit
in
Fig.
12
2a
is
the
same
as
in
Fig.
638
in
the
textbook.)
22 SwitchonthepowersupplyandadjustitsoutputforVCC 12V.
23 MeasureVB,VE,andVC,andrecordthevoltagesonthelaboratoryrecordsheet.
24 Connect the signal generator and oscilloscope to the circuit as illustrated inFig.122.
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R168k RC3.9k
VCC
12V
C3Circuitboard
C3
Powersupply
R2C110 F
0.12 FQ1
C2
180 F
R1
RL82k
C1R
RC
CB Q1E
Tooscilloscope
56k RE v4.7k E2 C2 RL
(a)Commonbasetestcircuit
Tooscilloscope
Signalgenerator
(b)Connectiondiagram
Figure 12-2 BJ T Common-base circuit and test equipment.
25 Setthesignalgeneratorfor3kHzsinewaveandadjustthesignalamplitudetogivea;1Voutputfromthecircuit.
26 Sketchtheinputandoutputwaveformsonthelaboratoryrecordsheetandrecordthepeakinputandoutputvoltagelevels.
27 Temporarilydisconnectthesignalgeneratorandconnecta56 resistor(Ra)inseries
withthe
signal
generator
and
the
circuit
input.
28 CheckthattheacsignalvoltagetoRa isthesameasthecircuitinputvoltagemeasuredinProcedure26.
29 Observetheamplitudeoftheacoutputvoltage.ChangetheresistanceofRa asnecessarytogiveanoutputamplitudewhichishalfofthatmeasuredinProcedure26.RecordtheresistanceofRaasthecircuitinputimpedance(Zi).
210 DisconnectRa,reconnectthesignalgenerator,andadjustthesignalleveltothatmeasuredinProcedure26onceagain.
211 Temporarilydisconnecttheloadresistor(RL)andsubstitutea3.9k resistor(Rb)forRL.
212 Observe theamplitudeof theacoutputvoltage.Change the resistanceofRb as
necessaryto
give
an
amplitude
which
is
half
of
that
measured
in
Procedure
26.
RecordtheresistanceofRb asthecircuitoutputimpedance(Zo).
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Analysis
1 From the resultsofProcedure1,plot thedcandac load lines for the common
collectorcircuit
and
show
the
maximum
output
voltage
swing.
2 Calculate the commoncollector circuit voltage gain (Av) from the results ofProcedure 16.Analyze the circuit to determineAv, and compare it to theAvcalculatedfromthemeasurements.
3 Analyze thecommoncollectorcircuit toestimateZi andZo.Compare thecalculatedvaluestothosemeasuredinProcedure1.
4 From the resultsofProcedure2,plot thedcandac load lines for thecommoncollectorcircuitandshowthemaximumoutputvoltageswing.
5 Calculate the commoncollector circuit voltage gain (Av) from the results ofProcedure26.AnalyzethecircuittodetermineAv,andcomparetotheAv calculatedfromthemeasurements.
6 AnalyzethecommoncollectorcircuittoestimateZiandZo.Comparethecalculated
valuesto
those
measured
in
Procedure
2.
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RecordSheetL12-1
RecordSheetLab.# 12 BJT CCandCB Circuit
Date
Procedure 1-3 VCC VB VE VC
Procedure 1-6Vi(pk) =
Vo(pk) =
Av =
Input
wavefor
m
Output
wavefor
m
Procedure 1-9 Zi =
Procedure 1-12 Zo =
Procedure2-3 VCC VB VE VC
Procedure2-6Vi(pk) =
Vo(pk) =
Av =
Input
wavefor
m
Output
wavefor
m
Procedure2-9 Zi =
Procedure2-12 Zo =
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LABORATORY
INVESTIGATION 9JFET Characteristics
Introduction
DrainandtransfercharacteristicsareconstructedforannchannelJFETbythepointbypointprocess.TheJFETisfirstconnectedinCSconfiguration,anditsgatevoltage(VGS)issetatzero.Thedrainsourcevoltage(V
DS) invariedinsteps,andthedraincurrent(I
D)
is noted at eachVDS step.This gives a tableof ID versusVDS levels fromwhich thedraincharacteristiccanbeplotted.TheprocessisrepeatedforseveralVGS levelstogiveafam ilyofdraincharacteristics.TheJFETtransfercharacteristicispreparedinasimilarwaybyholding VDS constantwhilevarying VGS andnoting the corresponding levelsofID andVGS.DraincharacteristicsarealsoobtainedbytheuseofanXYrecorder.
Equipment
2dcpowersupplies(0to20V)DCvoltmeter(0to25V)DCammeter(0to20mA)
Resistors(1k ,
0.25
W),
(1
M ,
0.25
W)
LowcurrentgeneralpurposenchannelJFET(e.g.,2N5486)CircuitboardXYrecorder
Procedure1 Drain Characteristics
11 ConnectthecircuitandtestequipmentasshowninFig.131aaccordingtotheconnectiondiagraminFig.131b.
12 Setbothpowersuppliesforzerooutput;thenswitchon.
13 Maintaining VGS constant, carefully adjust VDS to eachof thevoltages listed for
Procedure1on
the
laboratory
record
sheet.
Record
the
measured
IDat
each
VDS level
forVGS 0.
14 CarefullyadjustVGS to 1V;thenrepeatProcedure13toproduceatableofcorrespondingVGS andID levelsforVGS 1V.
15 RepeatProcedure13forVGS 2Vand 3V.
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ID
A
R
1
Powersupply
VGS V
1M Q1 V VDS Powersupply
Voltmeter
(a)JFETtestcircuit
Voltmeter Ammeter
V VV
A COM
VA COM
AVA COM
Powersupply
DR1 S
G
Q1
Circuitboard
(b)Connectiondiagram
Powersupply
Figure 13-1 Circuit and connection diagram for determining J FET characteristics.
Procedure2 TransferCharacteristics
21 Usingthesamecircuitas inFig.131,setVGS to0andVDS to10V.MeasuretheID level,andrecorditonthetableforProcedure2onthelaboratoryrecordsheet.
22 Maintaining VDS constant at 10V, adjust VGS to each of the voltages listed forProcedure 2 on the laboratory record sheet. Record the measured ID at eachVGSlevel.
Procedure3 Drain Characteristic Plotting on XY Recorder31 Connect the circuit and test equipment as shown in Fig. 132a according to the
connectiondiagraminFig.132b.
32 SetbothpowersuppliesforzerooutputandtheXYrecordersensitivityfor1V/cmverticaldeflectionandhorizontaldeflection.
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XYrecorder R21k
R1Q1
1MV
Drainpower
supply
V
Gatepowersupply
(a)JFETtestcircuit DrainpowersupplyV=
(1V/cm)
ID
VDS
XYrecorder
Vertical
Horizontal
R2
DS QG
R1
V/A COM
V=
(1V/cm)
Circuitboard
(b)Connectiondiagram
Gatepowersupply
V/A COM
Voltmeter
Figure 13-2 Use of an XY recorder to draw J FET drain characteristics.
33 InstallsuitableplottingpaperintheXYrecorder,switchontheXYrecorder,adjustitspentoasuitablezerovoltagestartingpoint,andlowerthepenontothepaper.
34 SlowlyincreasethedrainvoltagetoproduceasuitabletracerepresentingtheJFETdraincharacteristicforVGS 0.
35 RaisetheXYrecorderpenatthemaximumpointonthecharacteristic;thenreducethedrainsupplyvoltagetozero.
36 CarefullyincreasethegatepowersupplyvoltagetoproduceVGS 1V.
37 Lower thepen again; then slowly increase thedrainvoltage toproduce a tracerepresentingtheJFETdraincharacteristicforVGS 1V.
38Raise
the
XY
recorder
pen
at
the
maximum
point
on
the
characteristic;
then
reduce
thedrainsupplyvoltagetozero.
39 RepeatProcedures36through38forVGS levelsof 2Vand 3V.
310 RaisetheXYrecorderpenatthemaximumpointonthelastcharacteristicandremovethepaper.
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Analysis
1 PlottheJFETdraincharacteristicsfromtheresultsofProcedure1.
2Plot
the
JFET
transfer
characteristics
from
the
results
of
Procedure
2.
3 FromthedraincharacteristicforVGS 0,determinethevaluesoftherD andYosparameters.
4 From the transfer characteristic,determine thevalues of the Yfs parameters atVGS 1VandVGS 4V.
5 DrawhorizontalandverticalscalesonthedraincharacteristicsplottedbytheXYrecorder.IdentifyeachcharacteristicaccordingtotheVGS level.PrinttheJFETtypenumberonthecharacteristics.
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RecordSheetL13-1
RecordSheetLab.# 13 JFETCharacteristics
Date
Procedure 1 Drain Characteristics
(VGS = 0)
(VGS = 1 V)
(VGS = 2 V)
(VGS = 3 V)
VDS (V)
ID (mA)
ID (mA)
ID (mA)
ID (mA)
0.5 1 2 3 4 5 10
Procedure2 Transfer Characteristic
(VDS = 10 V)
VGS (V) 0
ID (mA)
1 2 3 4 5 6 7 8
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LABORATORY
INVESTIGATION 10JFET Bias Circuits
Introduction
ThreebasicJFETbiascircuitsareinvestigated:gatebias,selfbias,andvoltagedividerbias.Twotransistors(Q1andQ2)areusedtodemonstratetheeffectofdifferentVGS(off) andIDSSvalues.Eachcircuit isconstructed,and thedcvoltages throughout thecircuitaremeasured,firstwithQ1 inthecircuitandthenwithQ2.Theresultsarecomparedwithcircuits
inthe
textbook.
Equipment
DCpowersupply(0to20V)DCvoltmeter(0to20V)0.25Wresistors470k,270k,33k,12k,2.2k,1.2k,1k2 lowcurrent general purpose nchannel JFETs of different types (e.g., 2N5457 andMPF102)
Circuitboard
Procedure1 DeviceParameters and Gate Bias
11 IdentifythetwoJFETsasQ1andQ2;thenusingQ1,connectthegatebiascircuitandtestequipmentasshowninFig.141.
12 SwitchonthepowersuppliesandadjustVGS tozeroandVDD to18V.
13 MeasureIDandrecorditonthelaboratoryrecordsheetasthedrainsourcesaturationcurrentIDSS forQ1withVGS 0.
14 IncreaseVGS to 1VandmeasureID.RecordIDonthelaboratoryrecordsheetrecordforQ1withVGS 1V.
15 Increase VGS untilID fallstoapproximately0.1mA.
16 MeasureVGS andrecorditasthegatesourcecutoffvoltageVGS(off) forQ1withID 0.
17Switch
off
the
power
supplies
and
substitute
transistor
Q2 fortransistorQ1.
18 RepeatProcedures12through16usingJFETQ2.
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ID
A
R1
Powersupply
VGS V
1M Q1 V VDS Powersupply(a)Gatebiascircuit
Voltmeter Voltmeter Ammeter
V VV
A COM
VA COM
AV
A COM
Powersupply
R1DG
Q1
Circuitboard
(b)Connectiondiagram
Powersupply
Figure 14-1 J FET gate bias circuit and connection diagram.
Procedure2 JFET Self Bias
21 UsingtransistorQ1,connecttheselfbiascircuitandtestequipmentasshown inFig.142.
22 SwitchonthepowersupplyandadjustVDD to18V.
23 MeasureVD andVSandnoteonthelaboratoryrecordsheetfortransistorQ1.
24 SwitchoffthepowersupplyandsubstituteQ2 forQ1.
25 SwitchthepowersupplyonandagaincheckthatVDD 18V.
26 MeasureVD andVS againandrecordthevoltagesfortransistorQ2.
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Powersupply
RD4.7k
VDD
18V
Voltmeter
Circuitboard
RD
RS680
DV S
G
RS
VA COM
(a)Selfbias circuit (b)Connectiondiagram
Figure 14-2 J FET self bias test circuit.
Procedure3 JFET Voltage DividerBias
31 UsingtransistorQ1,connectthevoltagedividerbiascircuitandtestequipmentasshowninFig.143.
R1 RD
VDD
18VCircuitboard
Powersupply
2.2M
R2560k
2.7k
RS2.7k
Voltmeter
V
VA COM
R1 RD
DSG
R2 RS
(a)JFETvoltagedividerbiascircuit (b)Connectiondiagram
Figure 14-3 J FET voltage divider bias test circuit.
32 SwitchonthepowersupplyandadjustVDD to18V.
33Measure
VD,
VS,
and
VG and
note
the
levels
on
the
laboratory
record
sheet
for
the
voltagedividerbiascircuitwithQ1.
34 SwitchoffthepowersupplyandsubstituteQ2 forQ1.
35 SwitchthepowersupplyonandagaincheckthatVDD 18V.
36 MeasureVD,VS,andVGonceagainandnotethelevelsonthelaboratoryrecordsheetforthevoltagedividerbiascircuitwithQ2.
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Analysis
1 OnthelaboratoryrecordsheettabulatetheVDS levelsforeachbiascircuitfortran
sistorsQ1 and
Q2.
Use
VDS to
calculate
ID for
each
circuit
and
record
it
in
the
tableonthelaboratoryrecordsheet.2 Drawadcloadlineandmarkthebiaspointextremesforeachcircuit.3 ComparethecircuitstabilityforeachbiascircuittothesimilarcircuitsinSection105inthetextbook.
4 Using themeasuredVP and IDSS valuesand the ID levelsforVGS = 1V,drawapproximatemaximumandminimumtransfercharacteristicsforQ1andQ2.
5 Drawbias lines for each circuit on the transfer characteristics, and determineVDS(max) andVDS(min).Comparethecalculatedandmeasuredquantities.
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RecordSheetL14-1
RecordSheetLab.# 14 JFETBias Circuits
Date
Procedure 1 Gate BiasIDSS(VGS = 0) IDS(VGS = 1 V) VGS(off)
Transistor Q1
Transistor Q2
Procedure2 SelfBias
VDD VD VS ID = VS/RS
Transistor Q1
Transistor Q2
18 V
18 V
Procedure3 Voltage-DividerBias
Transistor Q1
Transistor Q2
VDD
18 V
18 V
VD VS VG
Analysis
VDS(min)
VDS(max)
Gate bias Selfbias Voltage divider
bias
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LABORATORY
INVESTIGATION 11Basic JFET Circuits
Introduction
AJFETcommonsourcecircuitisconstructedandtestedfordcconditions.Theacvoltagegain,inputimpedance,andoutputimpedancearemeasured.Thecircuitisthenconvertedinto commondrain and commongate configurations,and the acperformanceof eachconfigurationisinvestigated.
Equipment
DCpowersupply(0to25V)DCvoltmeter(0to25V)OscilloscopeSinusoidalsignalgenerator;1V,3kHz0.25Wresistors(2 2.7k),120k,1M,5.6M25Vcapacitors(0.02 F,0.15 F,10 F)LowcurrentgeneralpurposenchannelJFET(e.g.,2N5486)
Circuitboard
Procedure1 Common-Source Voltage Gain
11 Construct thecircuit inFig.151. (This is thecircuit inFig.119 in the textbook.)Leavethesignalgeneratorandoscilloscopeunconnectedatthistime.
12 SwitchonthepowersupplyandadjustitsoutputforVDD 25V.
13 MeasureVG,VS,andVD.Recordthevoltagesonthelaboratoryrecordsheet.
14 ConnectthesignalgeneratorandoscilloscopetothecircuitasillustratedinFig.151.
15 Setthesignalgeneratorfrequencyto3kHzandadjustthesignalamplitudetogivea;1Voutputfromthecircuit.
16 Sketchtheinputandoutputwaveformsonthelaboratoryrecordsheet,andrecordthepeakinputandoutputvoltages.
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R15.6M RD2.7k
VDD
25V
C3
C1
0.02 F
vsR21M
Q1
RS2.7k
0.15 F
C210 F
RL120k
Tooscilloscope
R1
Tooscilloscope
RDC3
(a)Commonsourcetestcircuit
Signalgenerator
DC1 SQG
R2 RS
RLC2
Powersupply
Circuitboard
(b)Connectiondiagram
Figure 15-1 J FET common-sourcecircuit and test equipment.
Procedure2 Common-Source Input and Output Impedance
21 SetthesignalgeneratorasinProcedure15.
22 Temporarilydisconnect thesignalgeneratorandconnecta1M resistor (Ra) inserieswiththesignalgeneratorandthecircuitinput,asillustratedinFig.152.
R1
Ra C1
1MR1
1
Ra
Signalgenerator
vs R2 R2
(a)Circuitmodification (b)Connectiondiagram
Figure 15-2 Common-source circuit input resistance measurement.
23 CheckthatthesignalvoltageamplitudeappliedtoRa isthesameasthatmeasuredinProcedure16.
24 Observe the amplitudeof the circuit ac outputvoltage.Change the resistance ofRaasnecessarytogiveanoutputamplitudewhichishalfofthatmeasuredinProcedure15.RecordtheresistanceofRaasthecircuitinputimpedance(Zi).
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25 DisconnectRa,reconnectthesignalgenerator,andadjustthesignalleveltothatmeasuredinProcedure16onceagain.
26 Temporarilydisconnectthe loadresistor(RL)andsubstitutea2.7k resistor(Rb)
forRL.
27 Observetheamplitudeofthecircuitacoutputvoltage.ChangetheresistanceofRbasnecessarytogiveanoutputamplitudewhichishalfofthatmeasuredinProcedure16.RecordtheresistanceofRbasthecircuitoutputimpedance(Zo).
Procedure3 Common-Drain Circuit (Source Follower)
31 Modify the circuit to convert it into commondrain configuration as shown inFig.153. (RD isreplacedwithashortcircuit,and theoutput is takenat theJFETsourceterminal.)
R15.6M
C1
0.02 F
vs R21M RS
2.7k
VDD
25V
Q1
C3
0.15 F RL120k
Signalgenerator
Tooscilloscope
R1
C1
Tooscilloscope
C3
DS QG
R
VDD
(a)Common
drain
test
circuit
R2S
RL
Circuitboard
(b)Connectiondiagram
Figure 15-3 J FET common-draincircuit and test equipment.
32 SwitchonthepowersupplyandcheckthatitsoutputgivesVDD 25V.
33 RepeatProcedures15and16.
Procedure4 Common-Gate Circuit
41 ConvertthecommondraincircuitintoacommongatecircuitbymakingthemodificationsshowninFig.154.
42 SwitchonthepowersupplyandcheckthatitsoutputgivesVDD 25V.
43 RepeatProcedures15and16.
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R15.6M RD2.7k
Q1
VDD
25V
C2
C3
0.15 F
RL
Tooscilloscope
Tooscilloscope
C10.02 F
R21M RS2.7k 10 F vs 120k R1 RD
C2
C3
DS Q1
VDD
(a)CommongatetestcircuitSignalgenerator
G
R2 RSC1 RL
Circuitboard
(b)Connectiondiagram
Figure 15-4 J FET common-gate circuit and test equipment.
Analysis
1 FromtheresultsofProcedure13,plotthedcandacloadlinesfortheCScircuitandshowthemaximumoutputvoltageswing.
2 CalculatetheCScircuitvoltagegainfromtheresultsofProcedure16.3 Analyze theCScircuit todetermineAv,Zi,andZo.Compare thecalculatedandmeasured
values.
Comment
on
the
phase
relationship
between
the
input
and
output
waveforms.4 FromtheresultsofProcedure33,calculatetheCDvoltagegain.AnalyzethecircuittodetermineAvandcomparetothemeasuredAv.
5 FromtheresultsofProcedure43,calculatetheCGvoltagegain(Av).AnalyzethecircuittodetermineAv andcomparetothemeasuredAv.Commentonthephaserelationshipbetweentheinputandoutputwaveforms.
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RecordSheetL15-1
RecordSheet 1Lab.# 15 BasicJFETCircuits
Date
Procedure 1-3 VDD VG VS VD
Procedure 1-6Vi(pk) =
Vo(pk) =
Av =
Input
wavefor
m
Output
wavefor
m
Procedure2-4 Zi =
Procedure2-7 Zo =
Procedure3-3Vi(pk) =
Vo(pk) =
Av =
Input
wavefor
m
Output
wavefor
m
Procedure4-3Vi(pk) =
Vo(pk) =
Av
=
Input
wavefor
m
Output
wavefor
m
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LABORATORY
INVESTIGATION 12
Capacitor-Coupled BJT Amplifier
Introduction
ABJT capacitorcoupled commonemitter amplifier circuit consisting of two identicalstagesisconstructedandtestedfordcandacperformance.Eachstageisfirsttestedfordcconditionsandacvoltagegain(Av).Thecircuitoverallvoltagegain,frequencyresponse,andinputandoutputimpedancesarealsoinvestigated.
Equipment
DCpowersupply(0to25V)DCvoltmeter(0to25V)OscilloscopeSignalgenerator;1V,(50Hzto5kHz)0.25Wresistors120k ,2 (3.9k ,12k ,39k ,120k )25Vcapacitors0.12 F,2 (10 F,150 F)2lowcurrentgeneralpurposenpnBJTs(e.g.,2N3904)Circuitboard
Procedure1 DC Conditions
11 Constructthecircuit inFig.161.(This is thecircuit inFig.1218 inthe textbook.)Leavethesignalgeneratorandoscilloscopeunconnected.
12 SwitchonthepowersupplyandadjustitsoutputforVCC 24V.
13 MeasureVB, VE, andVC foreachstageand record thevoltageson the laboratoryrecordsheet.
Procedure2 AC Measurements
21Connect
the
signal
generator
and
oscilloscope
to
the
circuit
as
illustrated
in
Fig.
16
1.
22 Setthesignalgeneratorfrequencyto3kHzandadjustthesignalamplitudetogivea;1VoutputatthecollectorterminalofQ2.(Notethatitmaybenecessarytousearesistiveattenuator(typically560 and560k )toreducethesignalamplitude.)
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R1120k R312k R5C3 120k R712k
VCC
24V
C5
C1
10 Fvs
R2
2NQ1 3904
10 F
R6
2NQ2 3904
0.12 F
RL
rs 39k R43.9k 39k2 R83.9k 120kC4600 150 F 150 F
(a)Capacitorcoupledtwostageamplifier
Tooscilloscope
Tooscilloscope Powersupply
R7
R1 R3RL
R5C5
C3 C
SignalgeneratorC1
C2R2
CB Q1E
R6
B Q2E
C4
R4 R8
(b)Connectiondiagram
Figure 16-1 Two-stage capacitor-coupled BJ T amplifier.
23 Sketchtheinputandoutputwaveformsforeachstageonthelaboratoryrecordsheetandrecordthepeakvoltages.
24 Adjustthesignalfrequencyinstepsaslistedonthelaboratoryrecordsheet,takingcaretokeepthesignalamplitudeconstant.Recordtheoutputvoltageamplitudeateachsignalfrequency.
Procedure3 Input and Output Impedances
31Set
the
signal
generator
as
in
Procedure
22.
32 Temporarilydisconnectthesignalgeneratorandconnecta1.5k resistor(Ra)inserieswiththesignalgeneratorandthecircuitinput.
33 CheckthatthesignalvoltageamplitudeappliedtoRa isthesameasthatmeasuredinProcedure22.
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34 Observetheamplitudeofthecircuitacoutputvoltage.ChangetheresistanceofRaasnecessarytogiveanoutputamplitudewhichishalfofthatmeasuredinProcedure22.RecordtheresistanceofRaasthecircuitinputimpedance(Zi).
35Disconnect
Ra,
reconnect
the
signal
generator,
and
adjust
the
signal
level
to
that
measuredinProcedure22onceagain.
36 Temporarilydisconnecttheloadresistor(RL)andsubstitutea12k resistor(Rb)forRL.
37 Observetheamplitudeofthecircuitacoutputvoltage.ChangetheresistanceofRbasnecessarytogiveanoutputamplitudewhichishalfofthatmeasuredinProcedure23.RecordtheresistanceofRbasthecircuitoutputimpedance(Zo).
Analysis
1Compare
the
dc
voltages
for
each
stage
of
the
amplifier
to
the
design
levels
in
Example122inthetextbook.Explainanydifferences.2 FromtheresultsofProcedure23calculatethevoltagegainofeachstageandtheoverallvoltagegain.
3 Analyzethecircuittodeterminetheacvoltagegainforeachstageandtheoverallacvoltagegain.Comparethecalculatedandmeasuredquantities.
4 FromtheresultsofProcedure24,plotthe(lowerend)frequencyresponsefortheamplifier,andestimatethecircuitlowercutofffrequency(f1).Comparethemeasuredf1 tothedesignvalueusedinExample126.
5 DiscussthecircuitinputandoutputimpedancesasmeasuredforProcedure3.
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RecordSheetL16-1
RecordSheetLab.# 16 Capacitor-Coupled BJTAmplifier
Date
Procedure 1-3 VCC VB1 VE1 VC1 VB2 VE2 VC2
Procedure2-3Vi(pk) =
Vo1(pk) =
Vo2(pk) =
Av 1 =
Av2 =
Av =
Q1inputwavefor
m
Q1outputwavefor
m
Q2output
waveform
Procedure2-4
f(Hz) 30 50
Vo(V)
Av
70 100 150 200 300
f(Hz)
Vo(V)
Av
400 600 800 1 k 2 k 5 k 10 k
Procedures 3-4 and3-7
Zi =
Zo =
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3456
7891
2
3456
7891
2
34
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Log GraphPaper
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LABORATORY
INVESTIGATION 13Direct-Coupled BJT Amplifier
Introduction
ABJTdirectcoupledtwostagecommonemitteramplifiercircuitisconstructedandtestedfordcandacperformance.Thedcconditionsthroughthecircuitarefirstchecked;thentheacvoltagegain (A
v) is investigated foreach stage.Thecircuitoverallvoltagegainand
frequencyresponsearealsoinvestigated.
Equipment
DCpowersupply(0to25V)DCvoltmeter(0to25V)OscilloscopeSignalgenerator0.25Wresistors68k ,47k ,39k ,5.6k ,4.7k ,(2 3.9k )25Vcapacitors(2 150 F),15 F,0.47 FLowcurrentgeneralpurposenpnandpnpBJTs(2N3904and2N3906)
Circuitboard
Procedure1 DC Conditions
11 ConstructthecircuitinFig.171.(This isthecircuitinFig.1222inthetextbook.)Leavethesignalgeneratorandoscilloscopeunconnectedatthistime.
12 SwitchonthepowersupplyandadjustitsoutputforVCC 14V.
13 MeasureVB,VE,andVC foreachstageandrecordthevoltagelevelsonthelaboratoryrecordsheet.
Procedure2 AC Measurements
21 ConnectthesignalgeneratorandoscilloscopetothecircuitasillustratedinFig.171.
22 Setthesignalgeneratorfrequencyto3kHzandadjustthesignalamplitudetogivea;1VoutputatthecollectorterminalofQ2.
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R3R5
VCC
14VC3
R168k
5.6k 3.9kQ2
150 F
2N
C1
Q 2N3904
3906C4
15 Fs
R2
0.47 F
RL
rs600
47k R44.7k C2150 F R63.9k 39k
(a)Directcoupledtwostageamplifier
To
oscilloscope
(vi) (vo1)
Powersupply
R1 R3 R53
SignalgeneratorC1
CB Q1E
EB Q2C
C4Tooscilloscope
C2
R6R2
R4
RL(vo2)
(b)Connectiondiagram
Figure 17-1 Two-stage direct-coupled BJ T amplifier.
23 Sketch the input and outputwaveforms for each stage on the laboratory recordsheet,andrecordthepeakvoltagelevels.
24 Adjustthesignalfrequencyinstepsaslistedonthelaboratoryrecordsheet,takingcaretokeepthesignalamplitudeconstant.Recordtheoutputvoltageamplitudeateachsignalfrequency.
Procedure3 Input and Output Impedances
31 SetthesignalgeneratorasinProcedure22.
32 Temporarilydisconnectthesignalgeneratorandconnecta1k resistor(Ra)inserieswiththesignalgeneratorandthecircuitinput.
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33 CheckthatthesignalvoltageamplitudeappliedtoRa isthesameasthatmeasuredinProcedure22.
34 Observe the amplitude of the circuit ac outputvoltage.Change the resistance of
Raasnecessary
to
give
an
output
amplitude
which
is
half
of
that
measured
in
Proce
dure22.RecordtheresistanceofRaasthecircuitinputimpedance(Zi).
35 DisconnectRa,reconnectthesignalgenerator,andadjustthesignalleveltothatmeasuredinProcedure22onceagain.
36 Temporarilydisconnectthe loadresistor(RL)andsubstitutea3.9k resistor(Rb)forRL.
37 Observetheamplitudeofthecircuitacoutputvoltage.ChangetheresistanceofRbasnecessarytogiveanoutputamplitudewhichishalfofthatmeasuredinProcedure23.RecordtheresistanceofRbasthecircuitoutputimpedance(Zo).
Analysis
1 FromtheresultsofProcedure13,calculatethecurrentlevelsthroughoutthecircuit.2 Analyzethecircuittodeterminethedcconditions,andcomparetothemeasureddcvoltageandcurrentlevels.
3 FromtheresultsofProcedure23calculatethevoltagegainofeachstageandtheoverallvoltagegain.
4 Analyzethecircuittodeterminetheacvoltagegainforeachstageandtheoverallacvoltagegain.Comparethecalculatedandmeasuredquantities.
5 FromtheresultsofProcedure24,plotthe(lowerend)frequencyresponsefortheamplifierandestimatethecircuitlowercutofffrequency.
6Analyze
the
circuit
to
determine
the
lower
cutoff
frequency
for
stage
1and
the
circuit
lowercutofffrequency.Comparethecalculatedandmeasuredcutofffrequencies.7 DiscussthecircuitinputandoutputimpedancesasmeasuredforProcedure3.
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RecordSheetL17-1
RecordSheetLab.#17 Direct-Coupled BJTAmplifier
Date
Procedure 1-3 VCC VB1 VE1 VC1 VB2 VE2 VC2
Procedure2-3Vi(pk) =
Vo1(pk) =
Vo2(pk) =
Av 1 =Av2 =
Av =
Q1input
wavefor
m
Q1output
waveform
Q2 output
waveform
Procedure2-4
f(Hz) 30 50
Vo(V)
Av
70 100 150 200 300
f(Hz)
Vo(V)
Av
400 600 800 1 k 2 k 5 k 10 k
Procedures 3-4 and3-7
Zi =
Zo =
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Log GraphPaper
David A. Bell Electronic Circuits and Electronic Devices
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LABORATORY
INVESTIGATION 14
SCRCharacteristics
and 90 Phase Control
Introduction
ThecharacteristicsofanSCRarefirstdeterminedbyapplyingaconstantanodevoltage(VA)and increasing thegatecathodevoltage (VGK)until theSCRswitcheson.Thegatecurrentandvoltagearenotedattheswitchoninstant,andVAK ismeasuredafterswitchon.TheprocessisrepeatedwithdifferentlevelsofVA.AnSCR90phasecontrolcircuitisnext
constructed
and
tested
by
monitoring
the
ac
supply
and
load
waveforms
for
various
control
elementsettings.
Equipment
Twodcpowersupplies;(0to20V)Twodcvoltmeters(0to20V)DCammeter(0to100mA)DCammeter(0to20 A)Oscilloscope115V,60Hzvariablevoltagetransformer(variac)115V,60Hz,1:1isolatingtransformer
0.25W
resistors120
,270
,(2
1k),1.5k,2.2k0.5Wpotentiometer1.5k
3Wresistor100LowcurrentSCR2N5064Lowcurrentdiode1N914Circuitboard
Procedure1 SCRForwardCharacteristics
11 Construct the SCR circuit in Fig. 391a according to the connection diagram inFig.391b.
12Set
both
power
supply
voltages
to
zero;
then
switch
on
and
adjust
VA to
5V.
At
this
timeVGK,IG,andIA shouldallbezero.
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A
R4 IA1k
R1 R3
1.5k 1kV R2
SCR1
A
IG
VA
V VAK
G270 V
VGK
(a)Circuit
Voltmeter(VGK)
V
Ammeter(IG) KGA
Bottomview2N5064
Voltmeter(VAK) Ammeter(IA)
VA COM
AV
A COM V
Powersupply(VG)R4 V
A COM
AV
A COM
A
R3 K1 SCR1
R2
(b)Connectiondiagram
Powersupply(VA)
Figure 39-1 Circuit for investigating SCR characteristics.
13 SlowlyincreaseVGuntiltheSCRfires(IAsuddenlyincreases).RecordthelevelsofIGandVGK at(orjustbefore)theinstantIA increases.(Itmaybenecessarytorepeattheprocessseveraltimestogetaccuratemeasurements.Todoso,VG shouldbereducedtozero,andVAshouldbeswitchedoffandthenonagain.)
14 RecordVAK
andI
AwhentheSCRison.
15 ReduceVG tozero; thenswitchVA offandon,andagainnote the levelsofVAKandIA.
16 AdjustVA to10V.
17 Slowly increaseVG untiltheSCR firesagain.Record IG andVGK asexplained inProcedure13.RecordVAK andIAwiththeSCRon.
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18 ReduceVG tozero,andthenswitchVA offandonagain.
19 AdjustVA togiveVAK equalto15V.
110 SlowlyincreaseVG untiltheSCRfiresagain.RecordtheIG andVGK onceagainasexplained
in
Procedure
13.
Record
VAK andIAwiththeSCRononceagain.
111 ReduceVG tozeroandreconnecttheVGK voltmetertomeasureVA.ThenprogressivelyadjustVA to4V,3V,and2V,recordingVAK andIAateachstep.
112 DisconnectthevoltmetermeasuringVAK;then,observingIA,slowlyreduceVA from3Vtozero.NotethelowestlevelofIA thattheSCRconductsat(theholdingcurrent)beforeitswitchesoff.
Procedure2 SCR 90 Phase ControlCircuit
21 ConstructthephasecontrolcircuitshowninFig.392,keepingtheacsupplyoffand
the
variac
set
for
zero
output.
(This
is
the
circuit
designed
in
Example
20
2
in
the
textbook.)
115V60Hz
VariacIsolatingtransformer
R12.2k
R21.5k
SCR1
D1
R3120
RL100
(a)Circuit
Variac
Isolatingtransformer
R1
R2 D1
R3
SCR1AGK
RL
Vi
Tooscilloscope
VL
(b)Connectiondiagram
Figure 39-2 SCR 90 control circuit.
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22 AdjustpotentiometerR2 forminimumgatecathodevoltage(VGK).
23 SwitchontheacsupplyandadjustthevariactogiveVi 30Vpeakasmonitoredontheoscilloscope.
24Investigate
the
waveform
(VL)developedacrossRL forvarioussettingsofR2.Note
therelationshipbetweenVi andVL,andsketcheachwaveformontherecordsheet.
Analysis
1 PlottheSCRcharacteristicsfromtheresultsofProcedures13through110.2 DiscusstherelationshipbetweentheSCRanodecathodevoltageandthegatecurrentrequiredtofiretheSCR.
3 ExplaintheresultsofProcedures111and112.4 Notethemeasuredforwardonvoltage(VTM),thegatetriggeringcurrent(IG),andtheholdingcurrent(IH),andcomparethemtothespecifiedquantitiesfortheSCRused.
5 Discusstheloadwaveformproducedbythe90controlcircuitandtheeffectofadjustingR2.ComparetherangeofwaveformadjustmentwiththatspecifiedforExample202inthetextbook.
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RecordSheetL39-1
RecordSheet DateLab.# 39 SCR Characteristicsand 90 Phase Control
Procedure 1-3 and 1-4(VA = 5 V) IG VGK VAK IA
Procedure 1-5VAK IA
Procedure 1-7
(VA = 10 V) IG VGK VAK IA
Procedure 1-10
(VA = 15 V) IG VGK VAK IA
Procedure 1-11
Procedure 1-12
VA VAK
(V) IA
(mA)
IH =
4 V 3 V 2 V
Procedure2-4
R2(min) R2(max)
Vi
VL
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LABORATORY
INVESTIGATION 15SCRand TRIAC Control Circuits
Introduction
AnSCR180phasecontrolcircuitisconstructed,anditsoutput(load)waveformiscomparedtotheacsourcewaveform.Thecontrolelementisadjustedtodeterminethemaximumandminimumanglesoftheoutputwave.Thewaveformdevelopedacrossthecapacitorinthecontrolcircuitisalsoinvestigated.ATRIAC180phasecontrolcircuitisconstructedandtestedinasimilarwaytotheSCRcircuit.
Equipment
Oscilloscope115V,60Hzvariablevolta