11 - Differential Amplifiers Example: OpAmp ECSE 334...

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1 ECSE334 – Introduction to Microelectronics ECSE 334 Introduction to Microelectronics Roni Khazaka Lecture #11 ECSE334 – Introduction to Microelectronics 2 Khazaka - 2008 Differential Amplifiers Example: OpAmp Amplifies differential signal v D + - + - ( ) + = v v A v d o ECSE334 – Introduction to Microelectronics 3 Khazaka - 2008 Differential Amplifiers Practically: v CM + - + - ( ) 0 = = + v v A v d o Example: OpAmp Ideally , rejects common mode input CM CM o v A v = ECSE334 – Introduction to Microelectronics 4 Khazaka - 2008 Differential Amplifiers Note: v CM + - + - 2 D v 2 D v + - - + 2 D CM v v v = 2 D CM v v v + = + D d o v A v = ( ) + = v v A v d o Usually the input consists of both a common mode component and a differential mode component 2 + + = v v v CM In practice: CM CM D d o v A v A v + = ECSE334 – Introduction to Microelectronics 5 Khazaka - 2008 Differential vs. Single Ended Signaling Source Receiver Noise / Interference Signal Signal + Noise Single Ended Signaling ECSE334 – Introduction to Microelectronics 6 Khazaka - 2008 Differential vs. Single Ended Signaling Source Receiver Noise / Interference Common Mode Signal Signal + Noise Differential Signaling + - Common Mode Signal Diff. Sig. Interference affects each line equally Î Differential mode signal unaffected! Signal + Noise
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2 ECSE334 – Introduction to Microelectronics 7 Khazaka - 2008 MOS Differential Pair v + Q 2 R D v D1 v S Q 1 R D v D2 V DD -V SS I v o -+ v - + - v o v + v - + - ECSE334 – Introduction to Microelectronics 8 Khazaka - 2008 MOS Differential Pair: Common Mode Operation Q 2 R D v D1 v S Q 1 R D V DD -V SS I i D1 i D2 v o v CM + - v D2 From Symmetry: D DD D D R I V v v 2 2 1 = = 2 2 1 I i i D D = = 0 1 2 = = D D o v v v ECSE334 – Introduction to Microelectronics 9 Khazaka - 2008 MOS Differential Pair: Input Common Mode Range Q 2 R D v D1 v S Q 1 R D V DD -V SS I i D1 i D2 v o v CM + - v D2 For proper operation as an amplifier Q1 and Q2 must be in saturation mode. () 2 2 1 2 1 2 t GS n D D V v L W k I i i = = = D DD D D R I V v v 2 2 1 = = 2 OV n V L W k I = ECSE334 – Introduction to Microelectronics 10 Khazaka - 2008 MOS Differential Pair: Input Common Mode Range Q 2 R D v D1 v S Q 1 R D V DD -V SS I i D1 i D2 v o v CM + - v D2 D DD D D R I V v v 2 2 1 = = 2 OV n V L W k I = t GS OV V v V = L W k I V n OV = t n t OV GS V L W k I V V v + = + = ECSE334 – Introduction to Microelectronics 11 Khazaka - 2008 Power Supply Budget V DD -V SS 2 1 G G v v = D DD D D R I V
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This note was uploaded on 01/27/2011 for the course ECSE 334 taught by Professor Anashamoui during the Spring '10 term at McGill.

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11 - Differential Amplifiers Example: OpAmp ECSE 334...

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