HW3 - Questions

# HW3 - Questions - UNIVERSITY OF CALIFORNIA College of...

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UNIVERSITY OF CALIFORNIA College of Engineering Department of Electrical Engineering and Computer Sciences EE 105 Prof. Salahuddin Fall 2009 Homework Assignment #3 Due at the beginning of class on Tuesday, 9/22/09 Problem 1 [20 points]: BJT Transconductance In the amplifier circuit below, the silicon NPN BJT is maintained at 300K. It has emitter area = 100 μ m × 100 μ m, base dopant concentration B = 10 18 cm -3 , quasi-neutral base width W B = 0.2 μ m, and current gain β = 100. For simplicity, you may assume that the base is uncompensated, and that the Early effect is negligible. a) Calculate the DC-bias (“operating point”) collector current I C , i.e. for a base-emitter bias V BE = 0.75V. (Use the plot of mobility vs . dopant concentration provided in Homework Assignment #1 to determine the minority-carrier mobility in the quasi-neutral base, and then use the Einstein relation to determine the minority-carrier diffusion constant in the quasi-neutral base.) Is the BJT is operating in the active mode? b)

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## This note was uploaded on 10/05/2009 for the course EE 105 taught by Professor King-liu during the Fall '07 term at Berkeley.

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HW3 - Questions - UNIVERSITY OF CALIFORNIA College of...

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