10W-quiz-2-sol

10W-quiz-2-sol - ECE102 (Winter 2010), Quiz 2 Problem 1. In...

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Unformatted text preview: ECE102 (Winter 2010), Quiz 2 Problem 1. In the circuit below, both transistors are identical with k ( W/L ) = 2 mA/V 2 , = 0, and V t = 2 V. A) Find I if Q2 is in saturation, B) for what value of V A , Q2 will be in saturation (10pts). Q 1 Q 2 V A D1 I 5 V 2k I Part A: Assuming that Q1 is ON ( V GS 1 > V t ), Q1 will be in saturation as V D 1 = V G 1 (or V DS 1 = V GS 1 > V GS 1 V t ). Then: KVL 5 = 2 10 3 I D 1 + V GS 1 I D 1 = 0 . 5 k ( W/L )( V GS 1 V t ) 2 = 10 3 ( V GS 1 2) 2 Substituting for I D 1 in the first equation, we get: 5 = 2 10 3 10 3 ( V GS 1 2) 2 + V GS 1 2 V 2 GS 1 7 V GS 1 + 3 = 0 The two roots are V GS 1 = 0 . 5 (not correct as V GS 1 < V t ) and V GS 1 = 3 V. Then, 5 = 2 10 3 I D 1 + 3 I D 1 = 1 mA Since V GS 1 = V GS 2 and Q2 is in saturation, I = I D 1 = 1 mA. Part B: In order for Q2 to be in saturation, we need (note V A = V DS 2 ) V DS 2 > V GS 2 V t V A > 3 2 = 1 V Problem 2. Find the bias point and amplifier parameters (...
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This note was uploaded on 10/21/2011 for the course ECE 102 taught by Professor Gilman during the Spring '08 term at UCSD.

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10W-quiz-2-sol - ECE102 (Winter 2010), Quiz 2 Problem 1. In...

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