# hw9_su10 - ECE 442 Electronic Circuits Homework 9 Due...

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ECE 442 Electronic Circuits Homework 9 Due Friday July 23, 2010 1. In the current source shown in Fig. 1, the designer placed the diode connection on BJT Q2 by mistake. The component values were then adjusted to supply the desired DC value of the collector current I O =2mA to the external circuitry (not shown). Discuss the problems that prevent this circuit from being a good current source, despite having the proper output current value. Hint: Analyze the output voltage v O and output resistance R O of this circuit – do they have the properties that you would expect from a good current source? Figure 1. 2. Consider the BJT current source shown in Fig. 2, with =100, V A =50V, I S =10 -15 A, m=1 (external circuitry is not shown). a. Assume R E =0. Design the current source (give values of V BE , I REF , R ) to produce the output current I O =1mA at the output voltage of V O =0.5V. Calculate the value of output resistance R o . b. Assume R E is non-zero, i.e., emitter degeneration is applied. Derive expressions for the

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## This note was uploaded on 02/08/2012 for the course ECE 342 taught by Professor Nareshshanbhag during the Spring '11 term at University of Illinois, Urbana Champaign.

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hw9_su10 - ECE 442 Electronic Circuits Homework 9 Due...

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