07hw1

# 07hw1 - ECE287A Fall 2007 Problem Set#1 Handed Out October...

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ECE287A Fall 2007 Problem Set #1 Handed Out: October 2 Due date: October 11 Problem 1 Consider the 2 stage amplifier shown below. The drain efficiency and gain for the driver amplifier are 40% and 12dB, and for the power stage, they are 50% and 8dB, respectively. Compute the power-added efficiency for each stage, and the drain efficiency and power-added efficiency of the combined circuit. A2 A1 Problem 2 Consider a basestation amplifier that has a gain of 10dB, and produces a time-average RF output power of 30W. Compute and plot the power that is dissipated as heat in the transistor , as a function of the PAE achieved in the amplifier. Suppose the maximum temperature rise of the transistor junction above the heatsink temperature must be limited to 75 C in order to achieve adequate reliability; plot the maximum thermal resistance Rth that can be tolerated between junction and heatsink for the transistor vs amplifier PAE. (Note that thermal circuits satisfy T= Rth * Pdiss, where

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07hw1 - ECE287A Fall 2007 Problem Set#1 Handed Out October...

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