# Hwk6sol - GEORGIA INSTITUTE OF TECHNOLOGY SCHOOL OF ELECTRICAL AND COMPUTER ENGINEERING ECE 3080A Semiconductor Devices for Computer Engineering

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ECE 3080A: Homework #6, Solution November 19, 2007 Page 1 of 5 G EORGIA I NSTITUTE OF T ECHNOLOGY S CHOOL OF E LECTRICAL AND C OMPUTER E NGINEERING ECE 3080A: Semiconductor Devices for Computer Engineering and Telecommunication Systems Fall Semester 2007, Homework #6 SOLUTIONS 1. BJT: Dynamic Behavior (15 points) The common emitter output characteristic of a pnp BJT at room temperature is shown below. The simplified Hybrid-Pi equivalent circuit is to be used in modeling the low- frequency ac response of the transistor. Suppose I B = 5 μA and V EC = 10 V at the dc operating point. Determine the values of g m and r π to be employed in the Hybrid-Pi model. Solution: From inspection of the I C vs. V EC plot, one concludes I C 1.1 mA at the dc operating point. Using the simplified equivalent circuit model, assuming T = 300 K, we find: g m = qI C kT = 4.2510 ! 2 S r " = kT qI B = 5180 #

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ECE 3080A: Homework #6, Solution November 19, 2007 Page 2 of 5 2. BJT: Frequency Limitation (10 points) In a particular bipolar transistor, the base transit time is 20 percent of the total delay time. The base width is 0.5 μm and the base diffusion coefficient is D
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## This note was uploaded on 02/17/2010 for the course ECE 3025 taught by Professor Citrin during the Spring '08 term at Georgia Institute of Technology.

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Hwk6sol - GEORGIA INSTITUTE OF TECHNOLOGY SCHOOL OF ELECTRICAL AND COMPUTER ENGINEERING ECE 3080A Semiconductor Devices for Computer Engineering

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