25_Lecutre

25_Lecutre - EE 114 Lecture 25 R Dutton B Murmann 1...

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Unformatted text preview: EE 114 Lecture 25 R. Dutton, B. Murmann 1 EE114 (HO #29) Lecture 25 OTA Feedback Circuits (Part III) R. Dutton, B. Murmann Stanford University R. Dutton, B. Murmann 2 Poor Mans OTA Circuit With Cascodes Objective: increase low frequency loop gain precision EE114 (HO #29) V DD V xm V xp V o V BN I TAIL /2 I TAIL C s C f v o v i Magic battery biasing Magic battery biasing EE 114 Lecture 25 R. Dutton, B. Murmann 3 AC Equivalent Model Cascodes help increase low frequency loop gain roughly by the intrinsic device gain ~100 in the EE114 technology EE114 (HO #29) v i v o C L C f C s G m =g m /2 C gdn C gs /2 2r on R op Z c R on C x x s f f C C C C + + = ! ( ) ( ) ( ) op on r int v op on o r int v on on m on on m on on r int v op op mp op op mp op op r r a R R R a r r g r r ' g r R a r r g r r g r R 2 2 2 2 1 1 ! = " ! " ! " + = " ! " ! + = o m R G T ! = R. Dutton, B. Murmann 4 Impact of C gdn Z c ~ 1/g m if R op < r on But this is not the case here Using the result from lecture 10 EE114 (HO #29) v i v o C L C f C s G m =g m /2 C gdn C gs /2 2r on R op Z c R on C x s frequencie high at 1 DC near 1 1 1 ' g Z r r ' g R Z r sC R ' g Z m c op on m op c on Ltot op m c !...
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This note was uploaded on 11/02/2011 for the course EE 114 taught by Professor Murmann during the Fall '08 term at Stanford.

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25_Lecutre - EE 114 Lecture 25 R Dutton B Murmann 1...

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