Revisit of OP AMP Design

Revisited OP AMP design in a current project to design a single-ended OP amp with low power and narrow bandwidth. Below is a few tips summarized from the design:

1. Open loop is always stable.

2. Maximum loop gain, loop gain, and gain margin.
   Loop gain T=F*A,wk:corresponding to phase margin; F=0 for open loop, F=1 for a unity gain source follower (the worst case for stability);
Maximum loop gain, corresponding to 180 phase; phase margin =0;
gain margin = maximum loop gain - loop gain

3. Current mirror
    cascoded current mirror to improve current source impedance

4. high gain is achieved with telescopic or folded cascode topology;

5. Common mode feed back makes no sense for single-ended output

6. Input offset voltage,CMRR and PSRR to simulate with mismatch

7. Compensation of Op-amp: to move the location of poles.