Interpretiing data from Cadence stability analysis

[jdp721]

Hi.

For the following inverting amplifier config using fully diff folded cascode opamp:



should the loop gain found using STB analysis (CMDM = -1) equal to [ (open-loop gain of opamp) * (beta) ] ?
- or is the loop gain not so easy to be calculated? - because, my simulation result is not matching with such calculation!

(here, I used beta = feedback factor = 1/11, and the open loop gain was found from open loop simulation)

A reply in this regard will be very helpful :roll:

 

[dick_freebird]

I had enough trouble from the stb analysis (coming up
with absurd operating points and giving way-bogus loop
gain) that I gave up on it and went back to old school
methods. You just can't trust it to work each and every
time, like you need to ever get through your Monte Carlo
compliance analysis.