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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 smallsignal 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 smallsignal 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 highfrequency hybrid7t 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 unitygain bandwidth, H. (1 pts) Course: ECSE33O Page 9 of 11 Diodes:
i=1,(exp(v/n Vﬂl 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
210
gm =
VGS —Vl ,W
gm =knf(VGS V.X1+/1'Vm) gﬁmgr‘mM 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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