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Simulators >> Circuit Simulators >> How to simulate fully differential opamp?
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Message started by holddreams on Oct 10^th, 2008, 4:00am

Title: How to simulate fully differential opamp?
Post by holddreams on Oct 10^th, 2008, 4:00am

Does anyone who has ever used balun to simulate fully differential opamp with SC CMFB?

For DC Gain analysis, how to build up the test bench?
EE240 has one slide like that(DC_Gain_Bias, as in the attachment1).
The SC CMFB is introduced in Ken Martin's book(cmfb,as in the attachment2).

Here comes my questions:
1)How to deal with the SC CMFB during AC analysis? That is, how to connect non-overlapping clock(ph1,ph2)?
2)How to deal with the Vbias in the attachment2?

Thanks.

Title: Re: How to simulate fully differential opamp?
Post by holddreams on Oct 10^th, 2008, 4:02am

The attachment 2.

Title: Re: How to simulate fully differential opamp?
Post by Ken Kundert on Oct 10^th, 2008, 3:38pm

SpectreRF's PAC analysis.

Title: Re: How to simulate fully differential opamp?
Post by holddreams on Oct 10^th, 2008, 8:53pm

Ken Kundert wrote on Oct 10^th, 2008, 3:38pm:

SpectreRF's PAC analysis.

Thanks.
Is there any other way without using PAC analysis?

Title: Re: How to simulate fully differential opamp?
Post by holddreams on Oct 29^th, 2008, 7:06am

I have write a verilogA module to replace the SC CMFB part and run the AC simulation, the results seems to be reasonable. :)

Title: Re: How to simulate fully differential opamp?
Post by subgold on Nov 12^th, 2008, 4:11am

holddreams wrote on Oct 10^th, 2008, 8:53pm:

Ken Kundert wrote on Oct 10^th, 2008, 3:38pm:

SpectreRF's PAC analysis.

Thanks.
Is there any other way without using PAC analysis?

transient simulation would do.

Title: Re: How to simulate fully differential opamp?
Post by Tlaloc on Nov 12^th, 2008, 8:29am

Whenever I want a simple AC, STB, or XF with the SC CMFB, I break the feedback from the SC CMFB and replace it with a continuous time CMFB model. This gives me a very fast way of verifying the differential signal path of the amp. Since I am normally making switched cap circuits anyway, I can verify the operation of the SC CMFB at a higher level where the time penalty of running a PXF or PSTB is already going to be spent.

Title: Re: How to simulate fully differential opamp?
Post by idesign on Feb 22^nd, 2009, 2:08am

holddreams, is it possible you post the verilog-A of SC CMFB? tahnks