14 - BJT Diff. Pair with Active Load VCC ECSE 334...

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1 ECSE334 – Introduction to Microelectronics ECSE 334 Introduction to Microelectronics Roni Khazaka Lecture #14 ECSE334 – Introduction to Microelectronics 2 Khazaka - 2008 BJT Diff. Pair with Active Load v + Q 2 v c1 v E Q 1 v o V CC I v - v B1 v B2 -V EE Q 3 Q 4 ECSE334 – Introduction to Microelectronics 3 Khazaka - 2008 Short Circuit Transconductance v + Q 2 v c1 v E Q 1 V CC I v - -V EE Q 3 Q 4 2 id v + 2 id v i o id o m v i G = ECSE334 – Introduction to Microelectronics 4 Khazaka - 2008 Short Circuit Transconductance g m1 v π 1 v 1 + - v b1 g m2 v 2 v 2 + - v b2 i c1 r 1 r 2 3 3 || o e r r 4 e r i o g m4 v 4 v 4 + - 0 2 id v + 2 id v 4 o r r 4 1 o r 2 o r 0 ECSE334 – Introduction to Microelectronics 5 Khazaka - 2008 Short Circuit Transconductance () 2 || || || 2 3 1 4 1 3 3 1 4 id e m o o e id m v r g r r r r v g v = 2 2 3 1 4 2 4 4 2 2 id e m m id m m m o v r g g v g v g v g i + = = 2 3 1 4 2 id e m m m o v r g g g i + = m m m m g g g g = = = 4 2 1 1 = α e m r g id m o v g i = m m g G = ECSE334 – Introduction to Microelectronics 6 Khazaka - 2008 Systematic Input Offset Voltage v + Q 2 Q 1 V CC I v - -V EE Q 3 Q 4 Due to Base Current in Current Mirror 2 I 2 I 2 I 2 I p I β 2 1 2 + I Δ p I I I 2 1 2 2 + = Δ + = Δ p p I I 2 1 2 2 p I I Δ
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2 ECSE334 – Introduction to Microelectronics 7 Khazaka - 2008 Systematic Input Offset Voltage v + Q 2 v c1 v E Q 1 V CC I v - -V EE Q 3 Q 4 2 2 OS id V v + = + 0 T m id o m V I g v i G 2 α = = = 2 2 OS id V v = T p m OS V I I G i V 2 β = Δ = p T OS V V 2 = ECSE334 – Introduction to Microelectronics 8 Khazaka - 2008 Wilson Current Mirror v + Q 2 Q 1 V CC I v - -V EE Q 3 Q 4 Wilson Current Mirror lessens the effect of current mirror base voltage Q 5 1 o R 2 o R Has added advantage of higher R o1 Æ increase gain ( ) 2 1 || o o m d R R G A = Need to make R o2 Æ also large in order to take full advantage Æ Folded Cascode ECSE334 – Introduction to Microelectronics 9 Khazaka - 2008 Wilson Current Mirror with Folded Cascode v + Q 2 Q 1 V CC I v - -V EE Q 3 Q 4 V BIAS 1 o R 2 o R Q 5 Q 7 Q 6 II -V EE o v 4 4 1 o o r R 2 5 5 2 o o r R ( ) 2 1 || o o m d R R g A = ECSE334 – Introduction to Microelectronics 10 Khazaka - 2008 Multi-Stage Amplifier Example Differential Amplifier
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14 - BJT Diff. Pair with Active Load VCC ECSE 334...

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