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Questions about CMFB for 2 stage op amp

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princerock

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Hello,

I'm designing a 2 stage diff op amp (folded cascode plus common source) and now I want to add cmfb to it. However I have the following quesitons before doing the design.

1. I have to add cmfb network for both stages, i.e. I need two cmfb networks, is this right?

2. DT vs. CT. Is implementation by sc circuit easier than its CT counterpart?

3. If I use sc to implement, how can I do simulation in cadence ic? It is said that I can use ideal circuits, what does this mean?

4. Can I add the cmfb without influencing the origianl op amp in terms of dc gain, GBW and phase margin?

Thank you for your help!
 

sunking

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1. both one or two are ok, it depond on you circuit structure.
2. it depond on you circuit structure. if the circuit have no clock, you have to choice CT
3. use idea circuits is OK. and you can use .pss .pac
4. of course
 

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