# Sol4 - ECE 255 ELECTRONIC ANALYSIS AND DESIGN Homework 4...

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Vcc R1 R2 Rc Re Vcc v s R S ECE 255 ELECTRONIC ANALYSIS AND DESIGN Fall 2009 Homework 4 Solutions Problem 1 (Text 13.60) Compute A Vs The ac equivalent circuit for an amplifier is shown. Assume the capacitors have infinite value and that R S = 750 , R B = 100 k , R C = 100 k , and R 3 = 100 k . Calculate the voltage gain of the amplifier if the BJT Q -point is {50 μ A, 10 V}. Assume β 0 = 100 and V A = 75 V. d 75V 10V r 1.70M 50 A + = = μ ( 29 m g 38.92 50 A 1.95mS = μ = and 100 r 51.4k 1.95mS π = = ( 29 i V m C 3 d A g R R r 1.95m 48.6k 94.8 = - = - × = - ( 29 S i B π V V S B π R r 33.9 A A 94.8 92.8 R R r .75 33.9 = = - = - + + Problem 2 (Text 13.61) For β 0 = 100 see Problem 1 above (Text problem 13.60) π BB B π 60 r 30.8k and R R r 100k 30.8k 23.6k 1.95mS = = = = Ω = ( 29 i V m C 3 d A g R R r 1.95m 48.6k 94.8 = - = - × = - ( 29 S i B π V V S B π R r 23.6 A A 94.8 91.9 R R r .75 23.6 = = - = - + + Problem 3 Design a four resistor bias network to achieve the operating point given in Text problem 13.60 with the following restrictions, R th = R B , R C = R C , and V CC = 20 V. Assume V BE = V 0 = 0.7V. C R V 100k 50 A 5V = Ω× μ = E R V 5V = ( 29 ( 29 E R E V 50.5 A R 5V C B E I I R = + = μ = E R 99k = To determine R 1 and R 2 we have the following relationships: th 1 2 R R R 100k = = , ( 29 E 1 1 CC BE R 1 R R V V V 20 0.7 5 V R I I - - - - = = , and ( 29 E 1 1 BE R 2 R B R V V 0.7 5 V R I I I 0.5 A + + = = - - μ Since 1 2 R 2 R × , R 2 can not be larger than 150 k

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## This note was uploaded on 01/20/2010 for the course ECE 255 taught by Professor Staff during the Spring '08 term at Purdue University-West Lafayette.

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Sol4 - ECE 255 ELECTRONIC ANALYSIS AND DESIGN Homework 4...

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