Electronics-I Lecture 27

Electronics-I Lecture 27 - Lecture 27 Electronics I 1...

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Unformatted text preview: Lecture 27 Electronics I 1 Biasing using Collector-to-Base feedback resistor • Biasing for CE amplifiers • V CC = I E R C + I B R B + V BE • • I E insensitive to β if R C >> R B /( β +1) • R B determines the allowable swing at C V CB = I B R B = R B I E / ( β +1) 1 R R V V I B C BE CC E + β +- = Lecture 27 Electronics I 2 Biasing using a current source • R E is replaced by a constant current source • I is independent of values β and R B R B can be increased to provide high input resistance Bias stability is not affected Lecture 27 Electronics I 3 Biasing using a current source • Q 1 & Q 2 are matched pairs • Q 1 connected as a diode • Assuming high β neglecting base currents • I REF = [V CC – V BE – (– V EE )]/R Identical transistors have same V BE so I = I REF • Current I remains constant if Q2 remains in active region • Possible if collector voltage V > – V EE + V BE • Also known as Current Mirror Lecture 27...
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This note was uploaded on 12/12/2010 for the course EE 1 taught by Professor Shahidanwar during the Spring '10 term at NUCES.

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Electronics-I Lecture 27 - Lecture 27 Electronics I 1...

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