ECSE_330_april2007

ECSE_330_april2007 - '11 April 2007 MC 1 Final Examination...

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Unformatted text preview: '11 April 2007 MC 1 Final Examination Introduction to Electronics ECSE330 - Sec.001 (flfipfil 25th 2007, 2:00pm — 5:00pm Examiner: PrOf. RamesDAlaari Assoc Examiner: Prof. Roni Khazaka Signature: fl , 3/ Signature: é QKZK é __ 4M'lflflfilljl' . StudentName: TMCGilHD= l l: I ‘ J INSTRUCTIONS: o This is a CLOSED BOOK examination. No notes are permitted. 0 There are 2 pages of equations provided at the end of the questions. 0 The examination consists of 8 problems with the total possible points of 50. Partial point distribution is indicated in brackets. o The examination consists of 11 pages, including this page and the equation pages; make sure you have a COMPLETE exam book. 0 Faculty of Engineering STANDARD CALCULATOR permitted ONLY. 0 Show your work: Answers withoutjustification will not receive marks. State any assumption you find necessary to complete your answer. Course: ECSE33O Page 1 of 11 Question 1 14 pts) A voltage amplifier has its output connected back to its input as indicated in the figure below. a) Derive expressions for the output resistance (ROUT’) and input resistance (RIN’) of the amplifier. (1 pt) b) Derive the expression for the overall voltage transfer function (Vout/VS) of the amplifier. ( 0.5 pt) c) The circuit in part c) is now modified such that a coupling capacitor (Cc) is used to connect the output terminal (Vout) of the amplifier to the load resistor (R1) as shown below. Find the cutoff fre uenc and derive the ex ression for the modified transfer function T1 3 )=Vmfl§ of the amplifier. (1.5 pt) (1) Provide a Bode magnitude plot for T(s) derived in part (c) clearly showing all the relevant details. (lpt) Course: ECSE33O Page 2 of 11 Question 2 15 pts1 In the following circuit: D1 and D2 are identical diodes with n=2, VT = 25 mV and R1=1KQ. a) Use constant voltage drop model (CVDM) for the diodes to find the voltage transfer characteristic of the above circuit (plot Vout vs Vin for -5V<Vm<5V). (2 pts) b) Assume that Vin=1.5v+1"'vsin(20t) and (3 pts) I. Determine the state of each diode. II. Find the DC current going through the diodes that are “on”. III. Find the small-signal resistance of the diodes that are “on”, IV. Find the DC and AC components of the output voltage. Course: ECSE330 Page 3 of 11 Question 3 16 pts! Assume Vt = 1V, kn’ (W/L) = 2 AN2, 1 = 0 and both transistors are operating in the saturation mode. The current source as shown in the diagram supplies 0.25 A and all capacitors are large. Ignore CLM and body effect. Solve the circuit below for the DC values of : a) VD2 (2 ptS) 13) Vs1 (2 PtS) 0) Is (2 PtS) +1OV +10V 1kQ Course: ECSE33O Page 4 of 11 Question 4 13 points! Consider the following digital CMOS circuit with three logic inputs labeled as A, B, and C. Note: VDD is logic 1 and GND is logic 0. VDD Vout M6 Find Vout for each of the following input combinations. Explain in each case which transistors are ON and which ones are OFF. a) A=0 B=0 c=o. (1 pt) b) A=1 B=1 c=1. (1 pt) 0) A=O B=1 c=1. (1 pt) Course: ECSE330 Page 5 of 11 Question 5 (9 Points! Consider the following circuit. All F ETs are operating in saturation. V13!) V00 Q4 Qg fR eq [REF 0‘" lRou, _|:—' _Q, x IVGG vx a) Specify the type of amplifiers configured by Q1 and Q2 (1 pt) b) Draw the small signal equivalent circuit for the section of circuit containing Q3 and Q4. Also, find an expression for Req. (1.5 pts) For the following parts replace the loading effect of Q3 with Req. Ignore the channel length modulation but you must include the Body effect if needed. 0) Draw the small signal equivalent circuit of the entire amplifier circuit. (2 pts) d) Find expressions for Rin, Rx and Rout. (2.5 pts) e) Find expressions for Vout/Vx and Vout/V in. (2 pts) Course: ECSE330 Page 6 of 11 Question 6 18 pts): Consider the multistage BJ T amplifier shown below. In this circuit, VCC = 2.5V, IE1=2mA, RB: 2 kg, RC: 0.6 kg, R132: 0.2 kg, [3:99, and VA is infinite. I a) If IE1=2 mA, determine the value of Rm. (4 pts) b) If 132 is fixed to value you found in part (a) and IE1=2 mA, determine the minimum value for RC to keep Q1 is the active mode. (lpt) c) In order to generate the IE1=2 mA, the following current steering circuit is used, if all BJTs are identical with B=99, find RREF. (3 pts) Course: ECSE33O Page 7 of 11 Question 7 110 pts]: Consider the following amplifier circuit. All capacitors are infinite valued. "Vco I I <7 a) This is a two stage amplifier. Specify the type of the amplifiers used at each stage. (1 pt) b) Draw the small-signal model of the entire circuit and include the early effect. (2 pts) c) Derive an expression for Rom including the early effect. (2 pts) For the following parts ignore the early effect. (1) Find expressions for Rinl, Rin2, Routl, Rout2. (3 pts). e) Find expressions for the voltage gains, vout/vinz and Vout/Vsjg. (2 pts) Course: ECSE330 Page 8 of 11 Question 8 15 fits}: Draw the high-frequency hybrid-7t model of the BJ T. (2 pts) a) Derive an expression for the short circuit current gain, hfe=Ic/Ib. (2 pts) b) Derive an expression for the unity-gain bandwidth, H. (1 pts) Course: ECSE33O Page 9 of 11 Diodes: i=1,(exp(v/n Vfl-l FETm N OS: I . = C Cutoff. VGS < V! [D 2 0 Kn H" 0% . , W Trlode: VGS > V, [D = k" TIC/Gs — V, )VDS 2 V025 ] VDS < VGS ‘ V! V > V Saturation: GS ' 1,, = yr; [(1103 — V,)’ (1 + 1V,” ) Vos > V0.9 — V: L PMOS l Cutoff: VGS>K 10:0 KP;- Triode: Vos ‘< V: 1,, = k; gkrw —V,)Vm #1735] VD? > VGS - Vt < V Saturation: 0‘ ‘ 1,, =%k;%(Vm —V,)’(l+/1Vm) Vm < VGS _ VI Bodyeffect Im=lm+r(f“2¢,mat—F2») SMALL SIGNAL 2-10 gm = VGS —Vl ,W gm =knf(VGS -V.X1+/1'Vm) gfimgr‘m-M 38 E {C 1'5 ‘_-5 . (1—6055 a 13 = I/T :g_m . :(fl VT :aTC IE I re :E VA C __ gm :VT ,8 r0_ C 1 VT =Er; +1:— r” 21—8“); fl _(fl :— — a r” a fl=— M S Comm? PM“ 1 0(3— Two ~Fafic ...
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