electronis circuits lab 1

8/11/2019 Electronis Circuits Lab 1

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SRINIVASAN ENGINEERING COLLEGE

DEPT OF ELECTRONICS AND COMMUNICATION ENGINEERING

ANNA UNIVERSITY CHENNAI

REGULATION 2009

II YEAR/ III SEMESTER

EC2208 ELECTONICS CIRCUITS LABORATORY-I

LABMANUAL

ISSUE:01 REVISION:00

APPROVED BY PREPARED BY

Prof. B. REVATHI R.SANKAR GANESH, AP.

HOD/ECE R.ANBARASAN, Assistant Professor.


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ELECTRONICS LABI SRINIVASAN ENGINEERING COLLEGE PERAMBALUR/II YEAR, III SEM

ISSUE:01 REVISION:00 2

Preface

This laboratory manual is prepared by the Department of Electronics and communication

engineering for Circuits and Devices (EC2155). This lab manual can be used as instructional book for

students, staff and instructors to assist in performing and understanding the experiments. This manual

will be available in electronic form from Colleges official website, for the betterment of students.

Acknowledgement

We would like to express our profound gratitude and deep regards to the support offered by

the Chairman Shri. A.Srinivasan. We also take this opportunity to express a deep sense of

gratitude to our Principal Dr.B.Karthikeyan,M.E, Ph.D, for his valuable information and

guidance, which helped us in completing this task through various stages. We extend our hearty

thanks to our head of the department Prof.B.Revathi M.E, (Ph.D),for her constant encouragement

and constructive comments.

Finally the valuable comments from fellow faculty and assistance provided by the

department are highly acknowledged.


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INDEX

S.No TOPIC PAGENO

1 Syllabus 4

2 Lab Course Handout 5

3 Basics for bread board connection 8

4 Experiments

1. Fixed Bias amplifier circuit using BJT 10

2. Design and construct BJT Common Emitteramplifier using voltage divider bias (self-bias) with

and without bypassed emitter resistor.

16

3. Design and construct BJT Common Collector Amplifier using voltage 23

4. Darlington Amplifier using BJT. 26

5. Source follower with Bootstrapped gate resistance 32

6. Differential amplifier using BJT

35

7. Class A Power Amplifier 44

8. Class B Complementary symmetry power amplifier 50

9. Power Supply circuit - Half wave rectifier withsimple capacitor filter.

54

10. Power Supply circuit - Full wave rectifier withsimple capacitor filter

63

5 76


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ELECTRONICS CIRCUITS LAB

SYLLABUS

Expt No.1 Fixed Bias amplifier circuit using BJT

1. Waveforms at input and output without bias.

2. Determination of bias resistance to locate Q-point at center of load line.

3. Measurement of gain.

4. Plot the frequency response & Determination of Gain Bandwidth Product

Expt No.2 Design and construct BJT Common Emitter Amplifier using voltage

divider bias (self-bias) with and without bypassed emitter resistor.

1. Measurement of gain.


Expt No.3 Design and construct BJT Common Collector Amplifier using voltage

divider bias (self-bias).

1. Measurement of gain.2. Plot the frequency response & Determination of Gain Bandwidth Product

Expt No.4 Darlington Amplifier using BJT.

1. Measurement of gain and input resistance. Comparison with calculated values.


Expt No.5 Source follower with Bootstrapped gate resistance

1. Measurement of gain, input resistance and output resistance with and without

Bootstrapping. Comparison with calculated values.

Expt No.6 Differential amplifier using BJT

1. Measurement of CMRR.

Expt No.7 Class A Power Amplifier

1.Observation of output waveform.

2.Measurement of maximum power output.

3.Determination of efficiency.

4.Comparison with calculated values.

Expt No.8 Class B Complementary symmetry power amplifier

1.Observation of the output waveform with crossover Distortion.

2.Modification of the circuit to avoid crossover distortion.

3.Measurement of maximum power output.

4.Determination of efficiency.

5.Comparison with calculated values.

Expt No.9 Power Supply circuit - Half wave rectifier with simple capacitor filter.

33

1. Measurement of DC voltage under load and ripple factor, Comparison withcalculated values.

2. Plot the Load regulation characteristics using Zener diode.

Expt No.10 Power Supply circuit - Full wave rectifier with simple capacitor filter

1. Measurement of DC voltage under load and ripple factor, Comparison with

calculated values.

2. Measurement of load regulation characteristics. Comparison with calculated values


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LAB COURSE HANDOUT

Subject code :EC 2208

Subject Title : ELECTRONICS CIRCUITS Lab

Staff name : R. SANKAR GANESH & R.ANBARASAN

Scope and Objective of the Subject:

To FIND THE GAIN OF BJT TRANSISTOR AND POWER AMPLIFIERS

Course Plan / Schedule:

S.No Topics to be covered Learning objectives Page

No*

No. of

hours

1 Fixed Bias amplifier circuit using BJT To design and construct a common

emitter amplifier with fixed bias,

measurement of gain and gain-

bandwidth product by plotting its

frequency response.

3 hrs

2 BJT COMMON EMITTERAMPLIFIER USINGVOLTAGE

DIVIDER BIAS

To design and construct a common

emitter amplifier with self bias,



frequency response.

3hrs

3 BJT COMMON COLLECTORAMPLIFIER USING VOLTAGE

DIVIDER BIAS

To design and construct a common

collector amplifier with self bias,



frequency response.

3hrs

4 DARLINGTON AMPLIFIER USINGBJT

To construct a Darlington current

amplifier circuit, determination of

gain and input resistance and to plot

the frequency response characteristics

3hrs

5 SOURCE FOLLOWER WITH BOOTSTRAPPED GATE RESISTANCE

To construct a source follower 3hrs


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bootstrapped gate resistance amplifier

circuit and to measure the input and

output resistances.

6 DIFFERENTIAL AMPLIFIERUSING BJT

To construct a differential amplifier usingBJT and to calculate the CMRR 3hrs

7 CLASS - A POWER AMPLIFIER To construct a class A amplifier and

absorb the waveform3hrs

8 CLASS B COMPLEMENTARYSYMMETRY POWERAMPLIFIER

To construct a CLASS B amplifier and

absorb the waveform3hrs

9 HALF WAVE RECTIFIER To construct a halfwave rectifier to plot

its input and output waveform3hrs

10 FULL WAVE RECTIFIER To construct a full wave rectifier andmeasure DC resistance under load

3hrs

11 3hrs

12 3hrs

*-As in Lab ManualEvaluation

schemeInternal AssessmentEC

No.

Evaluation

Components

Duration Weightage

1 Observation Continuous 20%

2 Record Continuous 30%

3 Attendance Continuous 30%

4 Model lab 3hr 20%

EC

No.

Evaluation

Components

Duration Weightage

1 Observation Continuous 20%

2 Record Continuous 30%

3 Attendance Continuous 30%


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Timings for chamber consultation: Students should contact the Course Instructor in her/his

chamber during lunch break.

STUDENTS GUIDELINES

There are 3 hours allocated to a laboratory session in Circuits and Devices Lab. It is a necessary

part of the course at which attendance is compulsory.

Here are some guidelines to help you perform the Programs and to submit the reports:

1. Read all instructions carefully and proceed according to that.

2. Ask the faculty if you are unsure of any concept.

3. Give the connection as per the diagrams.

4. After verification by the faculty, tabulate the readings.

5. Write up full and suitable conclusions for each experiment and draw the graph.

6. After completing the experiment complete the observation and get signature from the staff.

7. Before coming to next lab make sure that you complete the record and get sign from the

faculty.

STAFF SIGNATURE HOD


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BREADBOARD

The breadboard consists of two terminal strips and two bus strips (often broken in the

centre). Each bus strip has two rows of contacts. Each of the two rows of contacts are a node.

That is, each contact along a row on a bus strip is connected together (inside the breadboard). Busstrips are used primarily for power supply connections, but are also used for any node requiring a

large number of connections. Each terminal strip has 60 rows and 5 columns of contacts on each

side of the centre gap. Each row of 5 contacts is a node. You will build your circuits on the

terminal strips by inserting the leads of circuit components into the contact receptacles and

making connections with

Incorrect connection of power to the ICs could result in them exploding or becoming very

hot with the possible serious injury occurring to the people working on the experiment! Ensure

that the power supply polarity and all components and connections are correct before switching

on power .

Fig 1. The breadboard. The lines indicate connected holes.


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BUILDING THE CIRCUIT

The steps for wiring a circuit should be completed in the order described below:

1. Turn the power (Trainer Kit) off before you build anything!2. Make sure the power is off before you build anything!

3. Connect the supply and ground (GND) leads of the power supply to the power and ground

bus strips on your breadboard.

4. Plug the devices you will be using into the breadboard.

5. Mark each connection on your schematic as you go, so as not to try to make the same

connection again at a later stage.

6. Get one of your group members to check the connections, before you turn the power on.

7. If an error is made and is not spotted before you turn the power on. Turn the power off

immediately before you begin to rewire the circuit.

8. At the end of the laboratory session, collect you hook-up wires, devices and all equipment

and return them to the demonstrator.

9. Tidy the area that you were working in and leave it in the same condition as it was before

you started.

Common Causes of Problems:

1. Not connecting the ground and/or power pins.

2. Not turning on the power supply before checking the operation of the circuit.

3. Leaving out wires.

4. Plugging wires into the wrong holes.

5. Modifying the circuit with the power on.

In all experiments, you will be expected to obtain all instruments, leads, components at

the start of the experiment and return them to their proper place after you have finished the

experiment. Please inform the demonstrator or technician if you locate faulty equipment.


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1.FIXEDBIASAMPLIFIERCIRCUIT

1.1.AIM:

Toconstructafixedbiasamplifiercircuitandtoplotthefrequencyresponsecharacteristics.

1.2APPARATUSREQUIRED:

S.No. Name Range Quantity1. Transistor BC107 12. Resistor 10 k,100 k,680 1,1,13. Regulated power supply (0-30)V 14. Signal Generator (0-3)MHz 15. CRO 30 MHz 16. Bread Board 17. Capacitor 47F 2

CIRCUITDIAGRAM


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MODELGRAPH

f 1 FIG.9.2 f2 f

(Hz)

TAB.1.1:

FREQUENCYRESPONSEOFFIXEDBIASAMPLIFIER

Keeptheinputvoltageconstant(Vin)=

Frequency (in Hz) Output Voltage (in volts) Gain = 20 log (Vo / Vin) (in dB)

1.3.FORMULA:

a) R2/(R1+R2)=voltageatwhichClassA,ClassBorClassC

operationtakesplace


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b) hfe=Ic/Ib

1.4.THEORY:

Inordertooperatethetransistorinthedesiredregion,wehavetoapplyanexternaldcvoltage

of correctpolarityandmagnitude to the twojunctionsof the transistor. This is called biasingof the

transistor.

Whenwebiasatransistor,weestablishcertaincurrentandvoltageconditionsforthetransistor.

These conditionsare called operating conditionsordc operating point or quiescent point. This point

mustbestableforproperoperationoftransistor.Animportantandcommontypeofbiasing iscalled

FixedBiasing.Thecircuitisverysimpleandusesonlyfewcomponents.Butthecircuitdoesnotcheck

thecollectorcurrentwhichincreaseswiththeriseintemperature.

1.5.PROCEDURE

1. Connectionsaremadeasperthecircuitdiagram.

2. The waveforms at the input and output are observed for Class A, Class B and Class C

operationsbyvaryingtheinputvoltages.3. ThebiasingresistancesneededtolocatetheQ-pointaredetermined.

4. Settheinputvoltageas1Vandbyvaryingthefrequency,notetheoutputvoltage.

5. Calculategain=20log(Vo/Vin)

6. Agraphisplottedbetweenfrequencyandgain.

1.6.CALCULATIONS:

a) Todeterminethevalueofbiasresistace

R2/(R1+R2)

b) hfe=IC/IB

1.7.RESULT:

Thus,theFixedbiasamplifierwasconstructedandthefrequencyresponsecurveisplotted.The

GainBandwidthProductisfoundtobe=


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2.BJTAMPLIFIERUSINGVOLTAGEDIVIDERBIAS

2.1.AIM:

Toconstantavoltagedividerbiasamplifierandmeasureinputresistanceandgainandalsoto

plotthedccollectorcurrentasafunctionofcollectorresistance.

2.2.APPARATUSREQUIRED:

S.No. Name Range Quantity

1. Transistor BC 107 12. Resistor 56k,12k,2.2k,470 1,1,1,1

3. Capacitor 0.1F, 47F 2, 14. Function Generator (0-3)MHz 1

5. CRO 30MHz 1

6. Regulated power supply (0-30)V 1

7. Bread Board 1

FIG.5.1


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MODELGRAPH

f 1 FIG..2 f2 f (Hz)

TAB2.1:

Keeptheinputvoltageconstant,Vin=

Frequency (in Hz) Output Voltage (in volts) Gain= 20 log(Vo/Vin) (in dB)

2.3.FORMULA:

a) Rin=*Re

b) Gain=*Re/Rin


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2.4.THEORY:

ThistypeofbiasingisotherwisecalledEmitterBiasing.Thenecessarybiasingisprovidedusing3

resistors:R1,R2andRe.TheresistorsR1andR2actasapotentialdividerandgiveafixedvoltagetothebase.Ifthecollectorcurrentincreasesduetochangeintemperatureorchangein,theemittercurrent

Ie also increasesandthevoltagedropacrossRe increases,reducingthevoltagedifferencebetweenthe

baseandtheemitter.DuetoreductioninVbe,basecurrentIb andhencecollectorcurrentIc alsoreduces.

Thisreduction inVbe,basecurrent Ib andhencecollectorcurrent Ic also reduces.Thisreduction in the

collectorcurrentcompensatesfortheoriginalchangeinIc.

ThestabilityfactorS=(1+)*((1/(1+)).Tohavebetterstability,wemustkeepRb/Re assmallas

possible.HencethevalueofR1R2mustbesmall.IftheratioRb/Reiskeptfixed,Sincreaseswith.

5.PROCEDURE:

1. Connectionsaregivenasperthecircuitdiagram.

2. Measure the input resistance as Rin=Vin/Iin (with output open) and gain by plotting the

frequencyresponse.

3. Comparethetheoreticalvalueswiththepracticalvalues.

4. Plotthedccollectorcurrentasafunctionofthecollectorresistance(ie)plotofVcc andIc for

variousvaluesofRe.

2.6.RESULT:

Thus the voltage divider bias amplifier was constructed and input resistance and gain were

determined.TheGainBandwidthProductisfoundtobe=


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3.COMMONCOLLECTORAMPLIFIER

3.1AIM:

To construct a common collector amplifier circuit and to plot the frequency response

characteristics.



1. Transistor BC 107 12. Resistor 15k

,10k

,680

,6k

1,1,1,13. Capacitor 0.1F, 47F 2, 14. Function Generator (0-3)MHz 15. CRO 30MHz 16. Regulated power supply (0-30)V 17. Bread Board 1

CIRCUITDIAGRAM


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MODELGRAPH


TAB3.1:




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3.3THEORY:

Thed.cbiasingincommoncollectorisprovidedbyR1,R2andRE.Theloadresistanceiscapacitor

coupledtotheemitterterminalofthetransistor.

Whenasignalisappliedtothebaseofthetransistor,VBisincreasedanddecreasedasthe

signalgoespositiveandnegative,respectively.ConsideringVBE isconstantthevariationintheVB

appearsattheemitterandemittervoltageVEwillvarysameasbasevoltageVB.Sincetheemitteris

outputterminal,itcanbenotedthattheoutputvoltagefromacommoncollectorcircuitisthesameas

itsinputvoltage.Hencethecommoncollectorcircuitisalsoknownasanemitterfollower.

3.5PROCEDURE:

1.Connectthecircuitasperthecircuitdiagram.

2.SetVi=50mV,usingthesignalgenerator.

3.Keepingtheinputvoltageconstant,varythefrequencyfrom0Hzto1MHzinregularstepsandnote

downthecorrespondingoutputvoltage.

4.Plotthegraph;Gain(dB)Vs Frequency(Hz).

REVIEWQUESTIONS:

1.Whythecommoncollectoramplifierisalsocalledanemitterfollower?

2.Whatistheneedforcouplingcapacitors?

3.Whatwillbetheinput&outputimpedanceofcommoncollectoramplifier?

4.Writesomeapplicationsof commoncollectoramplifier.

5.Whatisthecurrentamplificationfactorofcommoncollector amplifier?

3.6.RESULT:

Thus, the Common collector amplifier wasconstructed and the frequency response curve is

plotted.TheGainBandwidthProductisfoundtobe=


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4.DARLINGTONAMPLIFIERUSINGBJT

4.1AIM:

To construct a Darlington current amplifier circuit and to plot the frequency response

characteristics.


S.No. Name Range Quantity1. Transistor BC 107 1

2. Resistor 15k

,10k

,680

,6k

1,1,1,13. Capacitor 0.1F, 47F 2, 14. Function Generator (0-3)MHz 15. CRO 30MHz 16. Regulated power supply (0-30)V 17. Bread Board 1

CIRCUITDIAGRAM


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MODELGRAPH


TAB4.1:




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THEORY:

In Darlingtonconnectionoftransistors,emitterofthefirsttransistorisdirectlyconnectedto

thebaseofthesecondtransistor.Becauseof directcouplingdcoutputcurrentofthefirststageis(1+hfe

)Ib1.If Darlingtonconnection for n transitor isconsidered, then due todirectcoupling thedcoutput

current foe laststage is (1+hfe )n times Ib1 .Due to very large amplification factor even two stage

Darlingtonconnectionhaslargeoutputcurrentandoutputstagemayhavetobeapowerstage.Asthe

poweramplifiersarenotusedintheamplifiercircuitsitisnotpossibletousemorethantwotransistors

intheDarlingtonconnection.

InDarlingtontransistorconnection,theleakagecurrentofthefirsttransistorisamplifiedbythe

secondtransistorandoverallleakagecurrentmaybehigh,Whichisnotdesired.

4.4PROCEDURE:


2.SetVi=50mv,usingthesignalgenerator.



4.Plotthegraph;Gain(dB)vs Frequency(Hz).

5.Calculatethebandwidthfromthegraph.

4.5.RESULT:

Thus, theDarlington current amplifier was constructed and the frequency responsecurve is

plotted..TheGainBandwidthProductisfoundtobe=

REVIEWQUESTIONS:

1. WhatismeantbyDarlingtonpair?

2.HowmanytransistorsareusedtoconstructaDarlingtonamplifiercircuit?

3.WhatistheadvantageofDarlingtonamplifiercircuit?

4.Writesomeapplicationsof Darlingtonamplifier.


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5.SOURCEFOLLOWERWITHBOOTSTRAPPEDGATERESISTANCE

5.1.AIM:

To construct a source follower with bootstrapped gate resistance amplifier and plot its

frequencyresponsecharacteristics.



1. Transistor BC107 2

2. Resistor 1k,11k,1Mk 1,1,1

3. Regulatedpowersupply (0-30)V 1

4. SignalGenerator (0-3)MHz 1

5. CRO 30MHz 1

6. BreadBoard 1

7. Capacitor 0.01F 2

FIG.13.1


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MODELGRAPH

f 1 f2 f (Hz)

FIG.13.2

TAB.5.1.

Keeptheinputvoltageconstant(Vin)=

frequency (in Hz) Output Voltage (in volts)

Gain = 20 log (Vo / Vin) (in dB)


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5.3.THEORY:

Source follower is similar to the emitter follower( the output source voltage follow the gate inputvoltage),the circuit has a voltage gain of less than unity, no phase reversal, high input impedance,low output impedance. Here the Bootstrapping is used to increase the input resistance byconnecting a resistance in between gate and source terminals.The resister RA is required to

develop the necessary bias for the gate.

5.4. PROCEDURE:

1.Connectionsaremadeasperthecircuitdiagram.

2. The waveforms at the input and output are observed for cascode operations by

varying the input frequency.

3.ThebiasingresistancesneededtolocatetheQ-pointaredetermined.

4.Settheinputvoltageas1Vandbyvaryingthefrequency,notetheoutputvoltage.

5.Calculategain=20log(Vo/Vin.)

6.Agraphisplottedbetweenfrequencyandgain.

RESULT:

Thus,theSourcefollowerwithBootstrappedgateresistancewasconstructedandthegainwas

determined.

REVIEWQUESTIONS:

1. Whatismeantbysourcefollower?

2. WhatismeantbyBootstrapping?

3. Howtheabovecircuit isusedtoprovideagoodimpedancematching?

. Whatistheadvantageofbootstrappingmethod?


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6.DIFFERENTIALAMPLIFIERUSINGBJT

6.1Aim: To construct adifferential amplifier usingBJT and to determine thedc collector currentof

individualtransistorsandalsotocalculatetheCMRR.


S.No. Name Range Quantity1. Transistor BC107 22. Resistor 4.7k, 10k 2,13. Regulated power supply (0-30)V 14. Function Generator (0-3) MHz 25. CRO 30 MHz 1

6. Bread Board 1

CIRCUITDIAGRAM

OBSERVATION

VIN=VO=AC= VO/VIN


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FORMULA:

CommonmodeGain (Ac)=VO/VIN

DifferentialmodeGain(Ad)=V0/VIN

WhereVIN=V1V2

CommonModeRejectionRatio(CMRR)=Ad/Ac

Where,Adisthedifferentialmodegain

Ac isthecommonmodegain.

THEORY:

The differential amplifier is a basic stage of an integrated operational amplifier. It is used to

amplifythedifferencebetween2signals.Ithasexcellentstability,highversatilityandimmunitytonoise.

Inapracticaldifferentialamplifier,theoutputdependsnotonlyuponthedifferenceofthe2signalsbut

alsodependsuponthecommonmodesignal.

TransistorQ1andQ2havematchedcharacteristics.ThevaluesofRC1 andRC2 areequal.Re1 and

Re2 are also equal and this differential amplifier is called emitter coupled differential amplifier. The

outputistakenbetweenthetwooutputterminals.


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OBSERVATION

VIN=V1V2

V0=

Ad=V0/VIN

For thedifferentialmodeoperation the input is taken from two differentsourcesand thecommon

modeoperationtheappliedsignalsaretakenfromthesamesource

CommonModeRejectionRatio(CMRR)isanimportantparameterofthedifferentialamplifier.

CMRRisdefinedastheratioofthedifferentialmodegain,Adtothecommonmodegain,Ac.

CMRR=Ad/Ac

Inidealcases,thevalueofCMRRisveryhigh.


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6.5.PROCEDURE:

1. Connectionsaregivenasperthecircuitdiagram.

2. Todeterminethecommonmodegain,wesetinputsignalwithvoltageVin=2V

anddetermineVoatthecollectorterminals.Calculatecommonmodegain,Ac=Vo/Vin.

3. To determine the differential mode gain, we set input signals with voltages V1 and V2.

Compute Vin=V1-V2 and find Vo at the collector terminals. Calculate differential mode

gain,Ad=Vo/Vin.

4. CalculatetheCMRR=Ad/Ac.5. Measurethedccollectorcurrentfortheindividualtransistors.

6.6.RESULT:

Thus, the Differential amplifier was constructed and dc collector current for the individual

transistorsisdetermined.TheCMRRiscalculatedas

REVIEWQUESTIONS

1.Whatisadifferentialamplifier?

2.Whatiscommonmodeanddifferentialmodeinputsinadifferentialamplifier?

3.DefineCMRR.

4.Whatiscommonmodesignal?

5. WritesomeapplicationsofDifferentialamplifier.


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7.CLASS-APOWERAMPLIFIER

7.1.AIM:

ToconstructaClassApoweramplifierandobservethewaveformandtocomputemaximum

outputpowerandefficiency.


S.No. Name Range Quantity1. Transistor CL100, BC558 1,12. Resistor 47k ,33 ,220, 2,13. Capacitor 47 F 24. Signal Generator (0-3)MHz 15. CRO 30MHz 16. Regulated power supply (0-30)V 17. Bread Board 1

CIRCUITDIAGRAM


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o L

TAB2.1:



7.3.FORMULA

Maximumpowertransfer=Po,max=V2/R

Effeciency,=Po,max/Pc

7.4.THEORY:

Thepoweramplifier issaidtobe ClassAamplifieriftheQpointandtheinputsignal

areselectedsuchthattheoutputsignalisobtainedforafullinputsignalcycle.

Forallvaluesofinputsignal,thetransistorremainsintheactiveregionandneverentersintocut-


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offorsaturationregion.Whenana.csignalisapplied,thecollectorvoltagevariessinusoidallyhence

the collectorcurrentalsovariessinusoidally.Thecollectorcurrentflowsfor3600 (fullcycle)oftheinput

signal.ietheangleofthecollectorcurrentflowis3600.

7.5PROCEDURE:


2.SetVi=50mv,usingthesignalgenerator.



4.Plotthegraph;Gain(dB)vs Frequency(Hz).

7.6.RESULT:

ThustheClassApoweramplifierwasconstructed.Thefollowingparameterswerecalculated:

a) Maximumoutputpower=

` b) Efficiency=

REVIEWQUESTIONS:

1. Whatismeantby PowerAmplifier?

2. WhatisthemaximumefficiencyinclassAamplifier.

3. WhatarethedisadvantagesofClassAamplifier?

4. WritesomeapplicationsofPoweramplifier.

5.WhatisthepositionofQ-pointinClassAamplifier?


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8.CLASSBCOMPLEMENTARYSYMMETRYPOWERAMPLIFIER

8.1.AIM:

ToconstructaClassBcomplementarysymmetrypoweramplifierandobservethewaveforms

withandwithoutcross-overdistortionandtocomputemaximumoutputpowerandefficiency.


S.No. Name Range Quantity1. Transistor CL100, BC558 1,12. Resistor 4.7k,15k 2,13. Capacitor 100F 24. Diode IN4007 25. Signal Generator (0-3)MHz 16. CRO 30MHz 17. Regulated power supply (0-30)V 18. Bread Board 1

CIRCUITDIAGRAM


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8.3.FORMULA:

Inputpower,Pin=2VccIm/

Outputpower,Pout=VmIm/2

PowerGainorefficiency,=/4(Vm/Vcc)100

8.4.THEORY:

ApoweramplifierissaidtobeClassBamplifieriftheQ-pointandtheinputsignalareselected

such that the output signal is obtained only for one half cycle for a full input cycle. The Q-point is

selectedontheX-axis.Hence,thetransistorremainsintheactiveregiononlyforthepositivehalfofthe

inputsignal.

There are two types of Class B power amplifiers: Push Pull amplifier and complementary symmetry

amplifier.In

the

complementary

symmetry

amplifier,

one

n-p-n

and

another

p-n-p

transistor

is

used.

Thematchedpairoftransistorareusedinthecommoncollectorconfiguration.Inthepositivehalfcycle

oftheinputsignal,then-p-ntransistorisdrivenintoactiveregionandstartsconductingandinnegative

halfcycle,thep-n-ptransistorisdrivenintoconduction.Howeverthereisaperiodbetweenthecrossing

ofthehalfcyclesoftheinputsignals,forwhichnoneofthetransistorisactiveandoutput,iszero

CIRCUITDIAGRAM

FIG.6.2


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OBSERVATION

OUTPUTSIGNAL

AMPLITUDE :

TIMEPERIOD :

CALCULATION

POWER,PIN =2VCCIm/

OUTPUTPOWER,POUT =VmIm/2

EFFICIENCY, =(/4)(Vm/VCC)x100

MODELGRAPH

FIG.6.3


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8.5.PROCEDURE:1. Connectionsaregivenasperthecircuitdiagramwithoutdiodes.

2. Observe thewaveformsandnote theamplitudeand time periodof the inputsignaland

distortedwaveforms.

3.

Connectionsare

made

with

diodes.

4. Observe thewaveformsandnote theamplitudeand time periodof the inputsignaland

outputsignal.

5. Drawthewaveformsforthereadings.

6. Calculatethemaximumoutputpowerandefficiency.

Hence thenatureof theoutputsignalgetsdistortedandno longerremains thesameasthe

input.Thisdistortioniscalledcross-overdistortion.Duetothisdistortion,eachtransistorconductsfor

lessthanhalfcycleratherthanthecompletehalfcycle.Toovercomethisdistortion,weadd2diodesto

provideafixedbiasandeliminatecross-overdistortion.

8.6.RESULT:

ThustheClassBcomplementarysymmetrypoweramplifierwasconstructedtoobservecross-

over distortion and the circuit was modified to avoid the distortion. The following parameters were

calculated:

a)Maximumoutputpower=

b)Efficiency=


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9.HALFWAVERECTIFIER

9.1.AIM:

To construct half wave rectifier with and without filter and to draw their input and outputwaveforms.



1. Transformer 230V/6-0-(-6) 1

2. Diode IN4007 1

3. Resistor 1k 1

4. Capacitor 100F 1

5. CRO 30MHz 1

6. BreadBoard 1

CIRCUITDIAGRAM:

WITHOUTFILTER:

FIG.13.1


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CIRCUITS AND DEVICES LAB MANUAL

SRINIVASAN ENGINEERING COLLEGE, PERAMBALURI YEAR

ISSUE: 01 REVISION: 00 38

WITHFILTER:

FIG.13.2

9.3.FORMULAUSED:

RippleFactor=

WhereImisthepeakcurrent

9.4.THEORY:

Halfwaverectifier:


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Arectifier isacircuit,whichusesoneormorediodestoconvertA.Cvoltage intoD.Cvoltage. Inthis

rectifierduringthepositivehalfcycleoftheA.Cinputvoltage,thediodeisforwardbiasedandconducts

for all voltages greater than the offset voltage of the semiconductor material used. The voltage

producedacrossthe loadresistorhassameshapeasthatofthepositive inputhalfcycleofA.Cinput

voltage.

Duringthenegativehalfcycle,thediodeisreversebiasedanditdoesnotconduct.Sothereisnocurrent

floworvoltagedropacrossloadresistor.Thenetresultisthatonlythepositivehalfcycleoftheinput

voltageappearsattheoutput.

9.5.PROCEDURE:

1. Connectthecircuitasperthecircuitdiagram.

2. Applya.cinputusingtransformer.

3. Measuretheamplitudeandtimeperiodfortheinputandoutputwaveforms.

4. Calculateripplefactor.

MODELGRAPH:

FIG.13.5


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TAB.9.1:

HALFWAVERECTIFIER:

Withoutfilter Withfilter

Inputsignal Outputsignal

Amplitude(V) Timeperiod Amplitude(V) Timeperiod

9.6.RESULT:

Thusthehalfwaverectifierwasconstructedandits

inputandoutputwaveformsaredrawn.Theripplefactorofcapacitivefilter

iscalculatedas

Ripplefactor=


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10.FULLWAVERECTIFIER

10.1.AIM:

Toconstructa fullwaverectifierand tomeasuredcvoltageunder loadandtocalculate the

ripplefactor.


S.No. Name Range Quantity1. Transformer 230 V / 6-0-(-6) 12. Diode IN4007 23. Resistor 1 k 14. Capacitor 100F 15. CRO 30 MHz 16. Bread Board 1

FULLWAVERECTIFIERWITHOUTFILTER


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FIG.8.1

FULLWAVERECTIFIERWITHFILTER

FIG.8.2


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10.3.FORMULA

RippleFactor=[(Im/2)/(2*Im/)]2

-1

WhereImisthepeakcurrent

10.4.THEORY:

The fullwave rectifierconducts forboththepositiveandnegativehalfcyclesof the inputac

supply. Inordertorectifyboththehalfcyclesoftheacinput,twodiodesareused inthiscircuit.The

diodesfeedacommonloadRLwiththehelpofacentretappedtransformer.Theacvoltageisapplied

through a suitable power transformer with proper turns ratio. The rectifiers dc output is obtainedacrosstheload.

Thedcloadcurrentforthefullwaverectifieristwicethatofthehalfwaverectifier.Thelowest

ripplefactoristwicethatofthefullwaverectifier.Theefficiencyoffullwaverectificationistwicethatof

halfwaverectification.Theripplefactoralsoforthefullwaverectifierislesscomparedtothehalfwave

rectifier.

PROCEDURE:

1. Connectionsaregivenasperthecircuitdiagramwiyhoutfilter.

2. Note theamplitudeand timeperiodof the inputsignalat thesecondarywindingof the

transformerandrectifiedoutput.

3. RepeatthesamestepswiththefilterandmeasureVdc.4. Calculatetheripplefactor.

5. Drawthegraphforvoltageversustime.

MODELGRAPH


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RESULT:Thus,thefullwaverectifierwasconstructedandtheripplefactorwascalculatedas

Ripplefactor =

10.5REVIEWQUESTIONS:

1. Whatismeantbyrectifier?

2. WritetheoperationoftwodiodesduringtheapplicationofACinputsignal

3. Whichtypeoftransformerusedfortherectifierinput?


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4. Defineripplefactor.

5. Writetheefficiencyofthisrectifier.

electronis circuits lab 1

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