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Unformatted text preview: Tufts University, ECE Dept.
Feb 22, 2008 BE 12: Homework # 5, Spring 2008 Due: Mar 03, 2008 1. For the Common—Base ampliﬁer shown in Figure—1: (a) Draw the small—signal model of the ampliﬁer. Assume the coupling capacitors(CCl, 002)
are shorts for the frequency of interest. Also neglect the output impedance (r0) of
the transistor. (b) From the smallsignal model derive AU,AUO,AZ,Zm, Zout and Power Gain (G) in
terms of the circuit parameters. (c) For RL = 10169, RC = 10199, VCC = 10V and Rs = 1009, to what value must
the bias current Idc be set in order that the input impedance Zm matches R3 (i.e.
Zm = 1009)? What is the resulting voltage gain from the source to the load ?
Assume a z 1. VT=2BMV 2. For the CommonBase ampliﬁer in Prob1 and for the values given in Prob—1(c), ﬁnd
the short—circuit two—port model parameters shown in F igure—2. where: Gm: in 'Ui 110:0 ‘ ’ __ A
G = M Lin‘
my. v0 vin=0 .
“'71 00:0
Z, = 13—2
1" vinzo BE 12: Homework # 5 Page 2 of 3 3. A certain NMOS transistor has W 2 10pm, L = 1pm, kn = 50nA/V2, and VT = 1V.
For the three circuits shown in Figure—3, ﬁnd the region of operation (ie. cut—off,triode
! or saturation) and using the appropriate equation determine the drain current (ID). lb ID V09 V135
__X___——'\ 2v ﬁ 3 ° 5V Figuve' 3 z (a) C b) (C) 4. In this problem you are trying to characterize a CommonEmitter ampliﬁer to create a
two—port equivalent circuit as shown in Figure—4. Based on measurement values extracted
experimentally, you can derive the the twoport model of the ampliﬁer. The experimental
setup is: 0 You are driving the ampliﬁer with lKHZ source with amplitude of 100mV (ie.
vs = 100mV  sin(wt)). o In series with the source is a 1009 resistance (ie. Rs = 1009). This source is AC
coupled which is assumed to be a short for this particular frequency. . o The load resistance is 12/69 (ie. RL = 2169). Following are measurement values for the given experimental setup: 0 The peak voltage measured at the input is 50mV (ie. Um = BOmV). o The peak voltage measured at the output, without the load, is 500mV (ie. vout
500mV). o The peak voltage measured at the output, with the load, is 333mV (ie. Um
333mV).  I ll Based on the measurement, determine the two—port model parameters, Zin, Z0, Gm. \ __  __  , ,
. ‘ p "2—Port model f0“
F‘qu c5 wph‘h‘wr. EB 12: Homework # 5 Page 3 of 3 5. Find the transfer function (0/1) for the given graph using Mason’s Gain formula. ...
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