Switched capacitor CMFB

[cjupiter]

switched capacitor cmfb

Im designing a switched capacitor sigma delta A/D converter so i thought it would be appropriate to use a switched capacitor CMFB circuit in my fully diff. folded cascode opamp.

I pretty much got the opamp circuit right except now i want to turn it into a subcircuit in SPICE. Since the CMFB circuit runs with non-overlapping clocks, would i just set a couple of input pins for the clocks in the subcircuit of the opamp. Or do i separate the CMFB circuit from the folded cascode op amp.

I was just wondering what would be the appropriate technique when implementing a fully diff amp with SC CMFB. If anyone could give me a little more insight on opamps with SC CMFB circuits that would be great. I have the texts by "Allen and Holberg" "Ravazi" and "Johns and Martin" and they got a bit on SC CMFB but not enough.

Cheers

 

[bastos4321]

I usually include the CMFB inside the ampop and enter the two clock phases as inputs.

bastos

 

[santhoshv78]

U can also test CMFB in stand alone mode..
Give the proper bias voltage as input and expect the same value at the output pin..

 

[nxing]

you can run PSS and PAC analysis to simulate opamp with SC-CMFB.

Good Luck