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lecture20annotat - 6.012 Microelectronic Devices and...

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6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 20-1 Lecture 20 - Transistor Amplifiers (II) Other Amplifier Stages November 17, 2005 Contents : 1. Common-source amplifier ( cont. ) 2. Common-drain amplifier 3. Common-gate amplifier Reading assignment: Howe and Sodini, Ch. 8, §§ 8.7-8.9
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6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 20-2 Key questions What other amplifier stages can one build with a sin- gle MOSFET and a current source? What is the uniqueness of these other stages?
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6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 20-3 1. Common-source amplifier with current-source supply V DD v s V GG v OUT i SUP i D R S R L signal source + - signal load V SS Loadline view: load line i SUP =I D V GG -V SS =V DD -V SS I SUP V GG -V SS V GG -V SS =V T 0 V SS V DD V OUT
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6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 20-4 Current source characterized by high output resistance: r oc . Then, unloaded voltage gain of common-source stage: | A vo | = g m ( r o //r oc ) significantly higher than amplifier with resistive supply. Can implement current source supply by means of p- channel MOSFET: V DD V B v s V GG v OUT i D i SUP R S signal source + - V SS
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± ± ± 6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 20-5 Relationship between circuit figures of merit and device parameters Remember: ± W g m = ² 2 µ n C ox I D L 1 L r o ± λ n I D I D Then: Circuit Parameters Device | A vo | R in R out Parameters g m ( r o //r oc ) r o //r oc I SU P W µ n C ox L - - - - - - adjustments are made to V GG so none of the other parameters change CS amp with current supply source is good voltage am- plifier ( R in high and | A v | high), but R out high too voltage gain degraded if R L ² r o //r oc .
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6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 20-6 Common-source amplifier is acceptable voltage amplifier (want high R in , high A vo ,low R out ): v s v in + + R out R S A vo v in R in R L v out + + ... but excellent transconductance
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lecture20annotat - 6.012 Microelectronic Devices and...

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