EE 330 Lect 36 Spring 2011

EE 330 Lect 36 Spring 2011 - EE 330 Lecture 36 High-Gain...

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EE 330 Lecture 36 High-Gain Amplifiers Digital Circuit Design Hierarchical Design Synthesis Basic Gate Operation
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High-gain amplifier V IN V OUT Q 1 V DD V EE I B V IN V OUT Q 1 m V 0 -g A g g m V BE V BE i B g π g 0 V IN V OUT CQ AF V t CQ AF t -I V A- V I /V V  8000 AF V t V 200V V 25mV   This gain is very large ! Review from Last Time
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Current Sources/Mirrors Q 0 V CC R Q 1 A E0 A E1 I 1 I 0 I 1 Multiple Outputs Possible Can be built at sourcing or sinking currents Also useful as a current amplifier MOS counterparts work very well and are not plagued by base current Review from Last Time
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High-gain amplifier V IN V OUT Q 1 V DD V EE I B 8000 V A How can we build the ideal current source? What is the small-signal model of an actual current source? Review from Last Time
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Basic Current Sources and Sinks V XX I X I X XX t V V X S E I = J A e I X V CC R CC X V -0.6V I R I X Basic Bipolar Current Sinks Basic Bipolar Current Sources I X V CC V YY I X V CC I X V CC I X V CC R Very practical methods for biasing the BJTs can be used Current Mirrors often used for generating sourcing and sinking currents Review from Last Time
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Basic Current Sources and Sinks Small-signal Model of BJT Current Sinks and Sources V XX I X g m V BE V BE i B g π g 0 g 0 Small-signal model of all other BJT Sinks and Sources are the same Review from Last Time
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High-gain amplifier V IN V OUT Q 1 V DD V EE I B m V 0 -g A g V IN V OUT Q 1 V EE V CC V YY m1 V 01 -g A 2g Nonideal current source decreased the gain by a factor of 2 But the voltage gain is still quite large Can the gain be made even larger? Review from Last Time
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High-gain amplifier Can the gain be made even larger? The Cascode Configuration Q 1 Q 2 V XX M 1 M 2 V XX M 1 M 2 V YY Q 1 Q 2 V YY Discuss
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The Cascode Amplifier (consider npn BJT version) Q 1 Q 2 V XX V IN V SS V OUT I B V CC Actually a cascade of a CE stage followed by a CB stage but usually viewed as a “single-stage” structure Cascode structure is widely used Discuss
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The Cascode Amplifier (consider npn BJT version) Q 1 Q 2 V XX V IN V SS V OUT I B V CC Q 1 Q 2 V IN V OUT
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The Cascode Amplifier (consider npn BJT version) Q 1 Q 2 V XX V IN V SS V OUT I B V CC Q 1 Q 2 V IN V OUT Q 1 Q 2 V 1 V X I X Instead of just determining the voltage gain, we will obtain the two-port model for the cascode amplifier
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Review of Two-Port Networks V 1 V 2 I 1 I 2 R IN R OUT A V V 1 A VR V 2 Two Port (Thevenin) V 1 V 2 I 1 I 2 g 22 g 21 V 2 g 12 V 1 g 11 Two Port (Norton) Two alternative two-port networks 1 11 1 21 2 2 21 1 22 2 I = g V + g V 1 in 1 VR 2 2 OUT 2 V 1 V = R I + A V V = R I + A V
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Review of Two-Port Networks V 1 V 2 I 1 I 2 R IN R OUT A V V 1 A VR V 2 Two Port (Thevenin) V 1 V 2 I 1 I 2 g 22 g 21 V 2 g 12 V 1 g 11 Two Port (Norton) Relationship between Thevenin and Norton two-port parameters 1 11 1 21 2 2 21 1 22 2 I = g V + g V 1 in 1 VR 2 2 OUT 2 V 1 V = R I + A V V = R I + A V IN 11 1 R= g 21 VR 11 g A =- g OUT 22 1 g 12 VR 22 g A =- g
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Review of Two-Port Networks V 1 V 2 I 1 I 2 g 22 g 21 V 2 g 12 V 1 g 11
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EE 330 Lect 36 Spring 2011 - EE 330 Lecture 36 High-Gain...

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