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MIT6_012F09_lec19

MIT6_012F09_lec19 - 6.012 Microelectronic Devices and...

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6.012 - Microelectronic Devices and Circuits Lecture 19 - Differential Amplifier Stages - Outline Announcements Design Problem - coming out tomorrow; PS #10 looks at pieces; neglect the Early effect in large signal analyses Review - Single-transistor building block stages Common source: general purpose gain stage, workhorse Common gate: small R in , large R out , unity A i , same A as CS v Source follower: large R in , small R out , unity A v , same A i as CS Series and Shunt feedback: we'll see in special situations Differential Amplifier Stages - Large signal behavior General features: symmetry, inputs, outputs, biasing (Symmetry is the key!) Large signal transfer characteristic Difference- and common-mode signals Decomposing and reconstructing general signals Half-circuit incremental analysis techniques Linear equivalent half-circuits Difference- and common-mode analysis Example: analysis of source-coupled pair Clif Fonstad, 11/17/09 Lecture 19 - Slide 1

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I BIAS -V +V 1 2 3 I BIAS -V +V 1 2 3 Linear amplifier layouts: The practical ways of putting inputs to, and taking outputs from, transistors to form linear amplifiers There are 12 choices: three possible nodes to connect to the input, and for each one, two nodes from which to take an output, and two choices of what to do with the remaining node (ground it or connect it to something). Not all these choices work well, however. In fact only three do: Name Input Output Grounded Common source/emitter 1 2 3 Common gate/base 3 2 1 Common drain/collector 1 3 2 (Source/emitter follower) Source/emitter degeneration 1 2 none Clif Fonstad, 11/17/09 Lecture 19 - Slide 2
I BIAS V - V + v out + - v in + - C E C O I BIAS V - V + v out + - v IN + - C O C I Three MOSFET single-transistor amplifiers V + + I BIAS C O v in - + v out - V - SOURCE FOLLOWER Input: gate Output: source Common: drain Substrate: to source I BIAS V - V + v in + - C E C O v out + - COMMON SOURCE Input: gate Output: drain Common: source Substrate: to source I BIAS V - + v out + - v IN + - C O C I COMMON GATE Input: source; Output: drain Common: gate Substrate: to ground v out + - v in + - v out + - v in + - v out + - v in + - Clif Fonstad, 11/17/09 Lecture 19 - Slide 3

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Single-transistor amplifiers with feedback V + + v in + C O V + R F C O + v out v out + - - v in - - R F I BIAS I BIAS C E C E V - V - SERIES FEEDBACK PARALLEL FEEDBACK* v out + - v in + - R F Clif Fonstad, 11/17/09 v out + - v in + - R F * Also termed "source degeneracy" Lecture 19 - Slide 4
Summary of the single transistor stages (MOSFET) MOSFET Voltage gain, A v Current gain, A i Input resistance, R i Output resistance, R o Common source " g m g o + g l [ ] = " g m r l ' ( ) # # r o = 1 g o \$ % & ( ) Common gate * g m + g mb [ ] r l ' * 1 * 1 g m + g mb [ ] * r o 1 + g m + g mb + g o [ ] g t + , - . / 0 Source follower g m [ ] g m + g mb + g o + g l [ ] * 1 # # 1 g m + g o + g l [ ] * 1 g m Source degeneracy (series feedback) * " r l R F # # * r o Shunt feedback " g m " G F [ ] g o + G F [ ] * " g m R F " g l G F 1 G F 1 " A v [ ] r o || R F = 1 g o + G F [ ] \$ % & ( ) Power gain, A p = A v " A i Note: When v bs = 0 the g mb factors should be deleted.

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MIT6_012F09_lec19 - 6.012 Microelectronic Devices and...

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