2002 - _ Middle East Technical University De artment of...

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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 ac-equivalent circuit. Estimate the upper 3dB frequency run using the open~eircuit time constants method. small-signal equivalent circuit: Time constant expressions: Q3 (25 pts) This question is two-page 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 R-m3. 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 _ shunt-shunt configuration to analyse the circuit. The Op-Amp’s open-loop gain is 104 VN, input resistance is 100k0hms, and output reistance is 1k0hms. a.) Calculate the voltage gain % . Draw-Feedback curcun here: Draw modified A-circuit 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. 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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.

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2002 - _ Middle East Technical University De artment of...

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