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Unformatted text preview: _ Middle East Technical University
De artment of Electrical and Electronics En ineerin
January 17, 2003 Duration:150 min. EB 31 1
Analog Electronics FINAL EXAM IMPORTANT NOTE : PLEASE READ BEFORE STARTING
.There are ﬁve questions; attempt all. .Use the reserved space to answer each question. .Show complete work for full credit. .Include units in your answers . Write legibly GOOD LUCK Surname : . . . . . . . . . . . . . . . .
Name : . . . . . . . . . . . . . . . .
Student No : . . . . . . . . . . . . . . . .
Signature : . . . . . . . . . . . . . . . . Section : . . . . . Q.l (20 pts) This question is two pages long.
Consider the circuit given below. Clearly state and reason if you make any assumptions in the
analysis. For the BJTs:
[3=]00
VA=80V R,
24K Rout
C40
Rs=lK C1
+
RL
v0 10K a) (4 pts) Find the DC operating points (1c, VCE)of the transistors in the given circuit.
Answer: b) (2 pts) Calculate the small signal parameters of the transistors.
Answer: b) (12 pts) Consider the circuit at high frequencies. Draw the small signal acequivalent
circuit. Estimate the upper 3dB frequency run using the open~eircuit time constants
method. smallsignal equivalent circuit: Time constant expressions: Q3 (25 pts) This question is twopage long.
Consider the following operational ampliﬁer. Attempt all 8 parts of this question even if you can
not answer some parts. +10 V  10 V
gli==10 mA/V, MI matched to M2, Q3 matched to Q4, rom= rem: roQ5= roQ5= no I303=Bos=l306=100 (3 pts) a) Find the differential mode input resistance of the second stage, Ring. .
Expression for Rin2= Value of Rin2= (6 pts) b) Draw the small signal differential mode half circuit of the ﬁrst stage including loading
by the second stage (in terms of Ring). Find the expression for the differential mode voltage gain of the ﬁrst stage (vol/vd) including the loading by the second stage and calculate it. Call this
gain, A“. No credit will be given unless you use half circuit analysis. Draw small signal differential mode half circuit in this
box Expression for Av1= Value ofAv1= (4 pts)‘ c) Write the expression for Rm3. No credit will be given unless you use the resistance
reﬂection rule (Le. transferring the equivalent effect of the emitter resistance to the base
circuit) Expression for Rin3= (4 pts) d) Write the expression for the differential mode small signal voltage gain of the second
stage (Av2=V02/Vol) including the loading of this stage by the following stage (in terms of Rin3). Expression for Avg: (1 pt) e) Write the approximate value of the small signal voltage gain AV]: Vog/Voz if R5<<B5R5.
Approximate value of Av3= (4 pts) 1‘) Write the expression for AV4=Vo/V03 and calculate it. Expression for Av4= Value of Av4== (3 pts) g) Find R5. R5= 0.4. (20 Pomts) .
Consider the feedback circuit given below. Use the feedback method for
_ shuntshunt conﬁguration to analyse the circuit. The OpAmp’s openloop gain is 104 VN, input resistance is 100k0hms, and output reistance is 1k0hms. a.) Calculate the voltage gain % . DrawFeedback curcun here: Draw modiﬁed Acircuit ere: b.) Calculate the input resistance Rin. c.) Calculate the output resistance Rout. Q5. (15 Points) .
a.) An ampliﬁer with a midband gain of 104 has gn_e pole at 10" Hz and Mg
poles at 105 Hz. Draw the Bode magnitude and phase plots to the scaled space provided below:
Use Bode plots to estimate what is the value of frequencyindependent W feedback factor for which the gain and the phase margins are zero? uuI"u Innanqunuqu:u II
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Amp is to be compensated by the addition of a third dominant pole to
operate stably with a phase margin of 45°. and feedback factor of 0.1; Draw
the Bode phase plot and locate the additional pole and show that the phase margin is 45° . £4.51; I.
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This note was uploaded on 05/25/2011 for the course EE 311 taught by Professor Murataskar during the Spring '11 term at Middle East Technical University.
 Spring '11
 MuratAskar

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