How to measure settling time of a differential opamp using spectreRF?

[Count]

Hi, I have a fully differential opamp using a switched capacitor CMFB.
I am able to perform a DCOP and AC analysis using PSS and PAC analysis
respectively. But I have a problem with the simulator to find out the
settling time of the opamp. My testbench for the settling time
analysis is the same as Figure 1 of
http://www.dessent.net/resume/ee240-dessent.pdf .
The problem I have with the traditional transient analysis is that the
CMFB has not settled down to the periodic DCOP. I tried running a PSS
first followed by the traditional transient analysis but the simulator
can't seem to work as the way as I want. Please suggest some ways.
Thanks a bunch!

 

[CFoley1064]

Hi, I have a fully differential opamp using a switched capacitor CMFB.

I am able to perform a DCOP and AC analysis using PSS and PAC analysis
respectively. But I have a problem with the simulator to find out the
settling time of the opamp. My testbench for the settling time
analysis is the same as Figure 1 of
http://www.dessent.net/resume/ee240-dessent.pdf .
The problem I have with the traditional transient analysis is that the
CMFB has not settled down to the periodic DCOP. I tried running a PSS
first followed by the traditional transient analysis but the simulator
can't seem to work as the way as I want. Please suggest some ways.
Thanks a bunch!

What's your simulation doing with DC input bias currents? Or are you using an
"ideal" op amp? Could that be part of your problem?

Good luck.
Chris