lec25 - 6.012 - Microelectronic Devices and Circuits - Fall...

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6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 25-1 Lecture 25 - Frequency Response of Ampli±ers (III) Other Amplifier Stages December 8, 2005 Contents : 1. Frequency response of common-drain ampli±er 2. Cascode ampli±er Reading assignment: Howe and Sodini, Ch. 9, § 9.3.3; Ch. 10, §§ 10.5, 10.7 Announcement: Final exam: December 19, 1:30-4:30 PM, duPont; open book, calculator required; entire subject under examina- tion but emphasis on lectures #19-26.
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6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 25-2 Key questions Do all amplifer stages suffer From the Miller effect? Is there something unique about the common drain stage in terms oF Frequency response? Can we make a transconductance amplifer with a large bandwidth?
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6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 25-3 1. Frequency response of common-drain am- pli±er v s V GG v OUT V DD V SS i SUP R S R L signal source + - signal load Features: voltage gain ± 1 high input resistance low output resistance •⇒ good voltage buffer
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6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 25-4 High-frequency small-signal model: G B S D + v s + - v gs + - - v bs v bs =0 + - v gs + - v out g m v gs r o R L R S + - v out g m v gs r o //r oc //R L =R L ' r oc C gd C gs C sb g mb v bs C db C gs C gd C db + v s - R S A v,LF = g m R ± L 1+ g m R ± L 1
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6.012 - Microelectronic Devices and Circuits - Fall 2005 Lecture 25-5 Compute bandwidth by open-circuit time constant tech- nique: 1. shut-off all independent sources, 2. compute Thevenin resistance R Ti seen by each C i with all other C ’s open, 3. compute open-circuit time constant for C i as τ i = R C i 4. conservative estimate of bandwidth:
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This note was uploaded on 07/20/2009 for the course ELECTRICAL 6.012 taught by Professor Prof.jesúsdelalamo during the Fall '05 term at MIT.

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lec25 - 6.012 - Microelectronic Devices and Circuits - Fall...

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