L18 lecture full

L18 lecture full - Offset Cancellation Overview Techniques...

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EECS 240 Lecture 18: Offset Cancellation B. Boser 1 Offset Cancellation Overview Techniques: – Correlated double sampling (CDS) – Chopper stabilization Reject offset and 1/f noise Alphabet soup – CDS: autozeroing, ping-pong opamp, self-calibrating opamp – Chopping: synchronous detection, dynamic element matching Reference – Ch. Enz and G. C. Temes, “Circuit Techniques for Reducing the Effects of Op-Amp Imperfections,” Proc. IEEE, Nov. 1996, pp. 1584-1614.
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EECS 240 Lecture 18: Offset Cancellation B. Boser 2 Output Offset Cancellation Output still corrupted by switch charge injection Æ bottom plate sampling Requires () in C os in out os C AV V V V A V AV V = = = : 2 Phase : 1 Phase DD os V AV <
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EECS 240 Lecture 18: Offset Cancellation B. Boser 3 Multistage Implementation R. Poujois and J. Borel, "A low drift fully integrated MOSFET operational amplifier," IEEE Journal of Solid-State Circuits, vol. 13, pp. 499 - 503, August 1978.
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EECS 240 Lecture 18: Offset Cancellation B. Boser 4 Results μV 5 < os V σ Differential implementation also uses chopper stabilization.
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EECS 240 Lecture 18: Offset Cancellation B. Boser 5 Input Offset Cancellation () 1 1 : (b) Phase 1 : (a) Phase , + = + = + = + = = = A V V A V V A V V V V A V A A V V V V V A V os res os os in o c os in o os o c o os o
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EECS 240 Lecture 18: Offset Cancellation B. Boser 6 Multistage Cancellation Open switches left to right Residual offset from S 1 … S N-1 (charge injection?) cancelled by final stage Capacitive coupling reduces gain Application: comparators
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EECS 240 Lecture 18: Offset Cancellation B. Boser 7 Offset Compensated SC Gain Stage S1 S2 C1 S1 C2 S2 S1 S2 V i V o V os V C1 V C2
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EECS 240 Lecture 18: Offset Cancellation B. Boser 8 SC Gain Stage: Φ 1 Assuming infinite open-loop gain. S1 C1 S1 C2 S1 S2 V i V o V os V C1 V C2 () os i C C tot os C os i C V C C V C V C V C Q V V V V V 2 1 1 2 2 1 1 2 1 1 + = + = = = Φ
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EECS 240 Lecture 18: Offset Cancellation B. Boser 9 SC Gain Stage: Φ 2 () i o tot tot os i tot os o tot os o C os C V C C V Q Q V C C V C Q V C C V C Q V V V V V 2 1 2 1 1 2
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This note was uploaded on 08/01/2008 for the course EECS 240 taught by Professor Boser during the Spring '04 term at Berkeley.

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L18 lecture full - Offset Cancellation Overview Techniques...

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