Question

(b) If the op-amp is realized by the circuit shown in Fig. 4( find the low-frequency gain and estimate the dominant pole pi as a function of the appropriate small-signal parameters and capacitor values. The unity-gain buffer has very high input resistance and very low output resistance. Assume that the voltage gain of the 2nd stage is very large and make any appro priate approximations. Then find the expression for the unity-gain frequency assuming that it is well within the 1-pole roll-off region of the open-loop magnitude frequency response. oui out Vin 9k ww Ce+Cd unity-gain buffer k M2 M2 Fig. 4(a) Fig. 4(b)

Answer 1

Sol Sgnce) If The ofa mp is realiz ed by The Cicuit Shoun in fiqceny gcuin fist ue find -be Tow fcm The Circuit Stage gain fiist Second stage ain = -gm2 (Yoy l Yos ) =- AZ A hird Stage gaum A, AL A3 gmy (904 11 Yos 7Gm, C10, Yau is aHonction of The Estimate he domindte Pole P Param etey and Capacito Valuy SmalSigna appyoPriate Draw he Given CirCuit Diag yam M3 ,1os Voot MI MI Unih Jain Buller tl 2- M2

-Gom -ihe aVe Circute The equivalont CiYCut is hp nd Slase my frist Slage Simplity Nou The above Civcoit by using miller Theerer is my =7 we write The Capaeitor Valu from The Ccoi NNow CtACty So, C2 7 C fYom the Crvcoi 'Yo Yo) Jm CYou os - 2CCet y). in PWe Get Substitule -the above gm You Yos ) (ctgdu)CYo, l Vo Dominat Rle P,s estimat ed

NOw W find.The Uni-gain fietueney ExPre ssion for -^ Tm This we assumeIhat t is Jell orthn the 1- Pole Yole-oft gegion of The Open loop magnitude frequency Yeponga A = Oni ain Band uidth Ther охор (Х m 3 = A ACee tgdyR AIAr Knouo 9m (Yo1 Yo) -1 SO 9m Ye YoA Unit gam Bad oidth - AC gdy) R )- Yo i llYo So Uni Cai width - 9m, Fs Uni Gain Banodth 1ente uni eain Bandoidth expredicn i's determined