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ee541F11HWSolutions01

ee541F11HWSolutions01 - EE 541 University of Southern...

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EE 541 University of Southern California Viterbi School of Engineering Choma Solutions, Homework #01 5 Fall Semester, 2011 U U U niversity of S S S outhern C C C alifornia USC Viterbi School of Engineering Ming Hsieh Department of Electrical Engineering EE 541: Solutions, Homework #01 Fall, 2011 Due: 08/31/2011 Choma Solutions Problem #01: The model shown within the symbolic network “box” in Figure (P1) is a small signal, and therefore linear, equivalent circuit of an emitter-degenerated, common emitter amplifier. The amplifier is driven by a voltage source whose Thévenin resistance is R s , and its load termination consists of a resistance, R l in shunt with a capacitance, C l . In this problem, R s = 50 , R l = 1.2 K , R e = 120 , and C l = 300 fF . The transistor model parameters are r b = 120 , r = 3.3 K , r o = 18 K , and = 220 amps/amp . I V s R s R e r b r C l R l I r o I 2 V 2 I 1 V 1 R out R in Figure (P1) (a). Derive analytical expressions for each of the four h-parameters of the degenerated common emitter amplifier. In the network box delineated in Figure (P1), the input port current, I 1 , is identical to the branch current, I , whence the controlled current satisfies I I 1 . The hybrid h-parameters, h 11 and h 21 , are each evaluated under the condition of a short circuited output port; that is, under the condition of V 2 = 0 . With V 2 = 0 , o 2 1 e 1 2 0 r I β I R I I , (P1-1) which leads immediately to 2 o e 2 21 1 o e V =0 β r R I h 218.54 amps/amp . I r R (P1-2) Note that h 21 is very close to parameter because r o >> R e . Continuing with V 2 = 0 , 1 b π 1 e 1 2 V r r I R I I , (P1-3) and using (P1-2) to eliminate current I 2 in this KVL relationship,
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