material1 / different / Chung-Yu Wu - Analog Circuit Design

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8 - 1

CHUNG-YU WU

Chapter 8 Advanced Design Techniques and Recent

Design Examples of CMOS OP AMPs

§8-1 Advanced Design Techniques of CMOS OP AMPs

§8-1.1 Improved PSRR and frequency compensation

8 - 2

CHUNG-YU WU

*Tracking RC compensation

Conceptual circuits :

The requires Rc is Rc = 1 / gm2 [1 + (Cd + CL ) / Cc] » 1 / gm 2[(Cc + C L ) / CC ] Thus LHP zero=LHP pole P2

and P3 becomes the second pole.

The stability considerations,

allows a smaller gm2 and larger C L

* RdsA » Rc indep of temperature, process , and supply variations. =>Tracking design to make sure that z=P2

=>No pole-zero doublet problem!

8 - 3

+VDD

-VSS

*M17,Cc : Tracking RC compensation.

*M9,M11:Sharing the separate n-well.

*VBIAS is not strictly independent of VDD and VSS.

§8-1.2 Improved frequency compensation technique.

Ref.: IEEE JSSC ,vol.sc-18, pp 629-633, Dec.1983

Grounded gate cascode compensation

+VDD