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EE 330 Lect 30 Fall 2011

# EE 330 Lect 30 Fall 2011 - EE 330 Lecture 30 Basic...

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EE 330 Lecture 30 Basic amplifier architectures

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How does g m vary with I DQ ? DQ OX m I L W C 2 μ g = ( 29 T GSQ OX m V V L W μ C g - = EBQ DQ T GSQ DQ m V 2I V V 2I g = - = Varies with the square root of I DQ Varies linearly with I DQ Doesn’t vary with I DQ Review from Last Time
Examples Compare the small-signal equivalent circuits of these two structures R 1 V IN V OUT R 1 V IN V OUT R B Since Thevenin equivalent circuit in red circle is V IN , both circuits have same voltage gain Review from Last Time

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Examples R 1 =2K Q 1 V OUT V CC =12V V IN (t) R B =500K C=1uF Several different biasing circuits can be used Biasing Circuit Review from Last Time
Examples Determine V OUTQ , A V , R IN Review from Last Time

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Examples Determine V OUT and V OUT (t) if V IN =.002sin(400t) Review from Last Time
Examples Determine the SS voltage gain β =100 R 1 V IN V OUT R B ss equivalent circuit Have seen this circuit before but will repeat for review purposes ss equivalent circuit m BE 1 g R OUT = - V V BE IN = V V V 1 m A R g = - CQ 1 V t I R A - V This basic amplifier structure is widely used and repeated analysis serves no useful purpose 177 V 2.3mA 2K A - 26mV - Review from Last Time

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Examples Determine the R IN β =100 R 1 V IN V OUT R B ss equivalent circuit IN in IN R = V i // in R B R r π = Usually R B >>r π // in R B R r r π π = CQ in t I R β V r π = Review from Last Time
Examples Determine V OUT and V OUT (t) if V IN =.002sin(400t) OUT OUTQ V IN V V +A V 7.4 .002 sin(400 ) OUT V -177 V t 7.4 .35 sin(400 ) OUT V - V t Review from Last Time

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Amplifier input impedance, output impedance and gain are usually of interest Why? y 11 y 11 V 2 y 21 V 1 y 12 V 2 V 1 Amplifiers can be modeled as a two-port Amplifier usually unilateral (signal propagates in only one direction: wlog y 12 =0) Thevenin equivalent output port often more standard Review from Last Time
Amplifier input impedance, output impedance and gain are usually of interest Examples: Assume amplifiers are unilateral       L IN OUT V IN L OUT S IN R R V = A V R +R R +R    OUT L IN VAMP V IN L OUT S IN V R R A = = A V R +R R +R Can get gain without recondsidering details about components internal to the Amplifier Why? Review from Last Time

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Amplifier input impedance, output impedance and gain are usually of interest Examples: Assume amplifiers are unilateral Can get gain without recondsidering details about components internal to the Amplifier Why?                   IN3 L IN2 IN1 OUT V3 V2 V1 IN L OUT3 OUT2 IN3 OUT1 IN2 S IN1 R R R R V = A A A V R +R R +R R +R R +R                   OUT IN3 L IN2 IN1 VAMP V3 V2 V1 IN L OUT3 OUT2 IN3 OUT1 IN2 S IN1 V R R R R A = = A
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