AEC Lab Manual

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Analog Electronic circuits Lab Manual- III-B.Tech-I-Sem, Department of Electrical & Electronics EngineeringA.Y. 2011-2012 1 EXPERIMENT-1. TRANSISTOR CE AMPLIFIER AIM: 1.To Measure the voltage gain of a CE amplifier 2.To draw the frequency response curve of the CE amplifier APPARATUS: TransistorBC547 Resistors 33K, 4.7K, 3.3K, 2.2K, 1.5K, 1K, 330, Capacitors[100F, 10F -2No,] Regulated power Supply (0-30V, 1A) Function Generator CRO, Bread Board, and Connecting Wires THEORY: TheCEamplifierprovideshighgain&widefrequencyresponse. Theemitterleadis commontobothinput&outputcircuitsandisgrounded.Theemitter-basecircuitis forwardbiased.Thecollectorcurrentiscontrolledbythebasecurrentratherthan emittercurrent.Theinputsignalisappliedtobaseterminalofthetransistorand amplifier output is taken across collector terminal. A very small change in base current produces a much larger change in collector current. When positive half-cycle is fed to theinputcircuit,itopposesforwardbiasofthecircuitwhichcausesthecollector currenttodecrease,whichinturncausestothevoltagetobecomemorenegative.Thus when input cycle varies through a negative half-cycle, increases the forward bias of the circuit, which causes the collectorcurrent to increases thus the output signal is common emitter amplifier is in out of phase with the input signal. Points to Remember: 1. It is the only configuration having both voltage and current gain. 2.There is 1800 phase difference between input & output.3. The roll off is approximately 20db per decade. 4.Prove that the Gain Bandwidth product is constant. Analog Electronic circuits Lab Manual- III-B.Tech-I-Sem, Department of Electrical & Electronics EngineeringA.Y. 2011-2012 2 Design Points: 1.Half the supply voltage across the transistor. 2.R3 should be reasonably low to have better frequency response. 3.1/10 Vcc across the emitter resistance. 4.The base voltage is emitter voltage + 0.7V. 5.10 times the base current is to be assumed flowing through R5 & R6. 6.S=10 CIRCUIT DIAGRAM: Analog Electronic circuits Lab Manual- III-B.Tech-I-Sem, Department of Electrical & Electronics EngineeringA.Y. 2011-2012 3 Design: A. Transistor has the following h-parameters.hfe=100;hie=1kO;hoe=17 mhos;hre=0.35x10-3.Vcc= 15V, IC=1mA,S=10. AVmid: RC = 2.5KO Assume VCEQ = Vcc /2,VE= VCC /10 , RE= VE/IC ,

VRC = Vcc - ( VCEQ+ VE). RC = VRC /IC, VB = VE+VBE = VCC (R2/(R1+R2)), RB= R1R2/R1+R2 FromtheaboveequationscalculatethevaluesofR1andR2whicharethebase biasing resistors. Calculation of SI & SII , PROCEDURE: 1.Connect the circuit as shown in circuit diagram 2.Apply the input of 1V peak-to-peak and 1 KHz frequency using Function Generator 3.Measure the Output Voltage Vo (p-p)A.) for various load resistors like 1K,5 K (0r) B.)Till you get unclipped output sine wave 4.Tabulate the readings in the tabular form. 5.The voltage gain can be calculated by using the expression A.)VVAiV0= (and) B.)Theoretically hR hAiec fef =Analog Electronic circuits Lab Manual- III-B.Tech-I-Sem, Department of Electrical & Electronics EngineeringA.Y. 2011-2012 4 6.ForplottingthefrequencyresponsetheinputvoltageiskeptConstantat20mV peak-to-peak and the frequency is varied from 100Hz to 1MHz Using function generator. 7.Note down the value of output voltage for each frequency with and without CE. 8. All the readings are tabulated and voltage gain in dB is calculated byUsing The Expression9. A graph is drawn by taking frequency on x-axis and gain in dB on y-axis on Semi-log graph.10.The band width of the amplifier is calculated from the graph using the expression, Bandwidth, BW= f2-f1, Where f1 - lower cut-off frequency of CE amplifier f2 - upper cut-off frequency of CE amplifier11.Calculate the gain bandwidth product of the amplifier using the expression Gain Bandwidth product = 3-dB Midband gain X BandwidthFREQUENCY RESPONSE (with gain expressed in db): Analog Electronic circuits Lab Manual- III-B.Tech-I-Sem, Department of Electrical & Electronics EngineeringA.Y. 2011-2012 5 OBSERVATIONS:With an Input voltage,Vi = 1v LOAD RESISTANCE (K) OUTPUT VOLTAGE (V0) Gain Gainindb WithCeWith out CeWithCeWith out CE FREQUENCY RESPONSE: Input voltage Vi= 1v FREQUENCY(Hz) OUTPUT VOLTAGE (V0) GAINindB Av=20 log10 (V0/Vi) WithCE With out CEWithCEWith out CE Analog Electronic circuits Lab Manual- III-B.Tech-I-Sem, Department of Electrical & Electronics EngineeringA.Y. 2011-2012 6 RESULT:ThevoltagegainandfrequencyresponseoftheCEamplifierare obtained. Also gain bandwidth product of the amplifier is calculated. VIVA QUESTIONS: 1.What is phase difference between input and output waveforms of CE amplifier? 2.What type of biasing is used in the given circuit? 3.If the given transistor is replaced by a p-n-p, can we get output or not? 4.What is effect of emitter-bypass capacitor on frequency response? 5.What is the effect of coupling capacitor? 6.What is region of the transistor so that it is operated as an amplifier? 7.How does transistor acts as an amplifier? 8.Draw the h-parameter model of CE amplifier? 9. On what factor the frequency response of an amplifier depends? INFERENCE: Output verified bySignature of faculty with date Analog Electronic circuits Lab Manual- III-B.Tech-I-Sem, Department of Electrical & Electronics EngineeringA.Y. 2011-2012 7 EXPERIMENT:2 A. TWO STAGE RC COUPLED AMPLIFIERWITH VOLTAGESERIES FEEDBACK AIM:Tocalculatevoltagegainoftwostagecascadedamplifierwithandwit hout voltage seriesfeedback also to observe frequency response. APPARATUS: i.Transistors- BC547- 2 Nos, ii.Resistors - [33k-2Nos, 4.7K,3.3K-2Nos,1k-2Nos, 330 - 2Nos,100-1Ns,] iii.Capacitors - [10uF- 3Nos, 100uF- 2Nos] iv.Switch-SPDT -1Nos v.Bread Board, vi.Regulatedpower supply vii.Cathode ray oscilloscope, CIRCUIT DIAGRAM: THEORY:Analog Electronic circuits Lab Manual- III-B.Tech-I-Sem, Department of Electrical & Electronics EngineeringA.Y. 2011-2012 8 This is the most popular type of coupling as it pro vides maximum bandwidthwith less complexity. A coupling capacitor is used to connect output of first stage to input of second stage.ResistancesR1,R2,RE formbiasingandstabilizationnetwork.Emitter bypass capacitor prevents a. c. signal to pass through RE. Cascade stages amplify signal and overall gain i increasesthe overall gain of two stages is A=A1*A2, WhereA1 = voltage gain of first stage A2 = voltage gain of second stage. When ac signal is applied to the base of the transistor, its amplified output appears at thecollectorofQ1.Itiscoupledtothesecondstageforfurtheramplification. Frequency response curve is obtained by plotting a graph between frequency and gain in db .The gain is constant in mid frequency range and gain decreases on both sides of the mid frequency range by 20db/decade. The gain decreases in the low frequency rangeduetotheinputtimeconstantfeatureRCandathighfrequenciesduetothe internal junction capacitances and effective output resistance. PROCEDURE: 1.Connect the circuit diagram as per the circuit with switch initially at position 1 2.Apply input voltage from the function generator to the circuit. 3.Observe the output waveform on CRO. 4.Measure the voltage ata.Output of first stage,b. Output of second stage. 5.Fromthereadingscalculatevoltagegainoffirststage,secondstageandoverall gain of two stages. Disconnect second stage and then measure output voltage gain of first stage. 6.Compare it with voltage gain obtained when second stage was connected. 7.Note down various values of gain for different frequencies. 8.A graph is plotted between frequency and voltage gain. 9.Repeat steps 2 to 8 by connecting the switch to node position 2. Analog Electronic circuits Lab Manual- III-B.Tech-I-Sem, Department of Electrical & Electronics EngineeringA.Y. 2011-2012 9 OBSERVATIONS:APPLIED FREQUENCY In Hz O/P VOLTAGE (Vo) VOLTAGE GAINin db = ) 20 (010logVVi With CeWithout CeWith CeWithout Ce 100 300 700 1K 3K 7K 10K 30K 70K 100K 300K 700K 1M 30M 70M 100M PRECAUTIONS: Transistor terminals must be identifying properly. Analog Electronic circuits Lab Manual- III-B.Tech-I-Sem, Department of Electrical & Electronics EngineeringA.Y. 2011-2012 10 FREQUENCY RESPONSE (with gain expressed in db): RESULT:Calculate the voltage gain of two stages cascaded amplifier with and without voltage series feedback, also observed the frequency response of that. VIVA QUESTIONS: 1)Which type of coupling is preferred and why? 2)What is loading effect? 3)Why it is known as RC coupling? 4)What is the purpose of emitter bypass capacitor? 5)What is the necessity of cascading? 6)What is 3dB bandwidth? 7)Why RC coupling is preferred in audio range? 8)Explain various types of Capacitors? 9) What are advantages of FET-BJT cascading? INFERENCE: Output verified bySignature of faculty with date Analog Electronic circuits Lab Manual- III-B.Tech-I-Sem, Department of Electrical & Electronics EngineeringA.Y. 2011-2012 11 EXPERIMENT:2B. TWO STAGE JFET AND BJT RC COUPLED AMPLIFIER AIM: a) To determine the frequency response of a two stage BJT and JFET Cascaded RC coupledamplifier,tomeasureupperandlowercutofffrequenciesofaCSandCE cascading amplifiers. b)Also to determine the input and output impedances, Zi and Zo respectively APPARATUS:1.Transistors - [ 2N3819 or BFW21 - 1No, Bc547- 1no] 2.Resistors - [680K 1No.,10k 2No.,3.3k 2No.,1k 2nos, 820 1No. ] 3.Capacitors[22 uF-2, 2.2uF -2, 1uF -2] 4.Oscilloscope(Scope/CRO) 5.Function Generator( FG) or Signal Generator 6.Digital millimeters (DMM)- Circuit Diagram: Analog Electronic circuits Lab Manual- III-B.Tech-I-Sem, Department of Electrical & Electronics EngineeringA.Y. 2011-2012 12 THEORY:Multistage amplifiers are made up of single transistor amplifiers connected in cascade.Thefirststageusuallyprovidesahighinputimpedancetominimize loadingthesource(transducer).Themiddlestageusuallyaccountformostofthe desiredvoltagegain.Thefinalstageprovidesalowoutputimpedancetoprevent loss of signal (gain),