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Simulators >> Circuit Simulators >> how to simulate fully differential amp with switch cap CMFB?
https://designers-guide.org/forum/YaBB.pl?num=1228274843

Message started by alicia8283 on Dec 2^nd, 2008, 7:27pm

Title: how to simulate fully differential amp with switch cap CMFB?
Post by alicia8283 on Dec 2^nd, 2008, 7:27pm

hi all,

i tried to simulate a fully differential amp which use switch cap as CMFB currently but i face trouble as the CMFB is timing dependant. i tried to connect the test circuit with ideal Balun as describe in "a test bench in differential circuits " which find in this forum but it seems have trouble. How should i test the differential amp with this switch cap?
thanks a lot.

Title: Re: how to simulate fully differential amp with switch cap CMFB?
Post by jbdavid on Dec 18^th, 2008, 8:25pm

I would make a State average model of the switch cap circuit, and use that for the small signal analysies.
jbd

Title: Re: how to simulate fully differential amp with switch cap CMFB?
Post by alicia8283 on Dec 18^th, 2008, 11:57pm

hi,

thanks a lot for your reply. Could you elaborate further on the method you mention?

Title: Re: how to simulate fully differential amp with switch cap CMFB?
Post by Ken Kundert on Dec 19^th, 2008, 8:23am

He is just suggesting that you replace the SC resistors with real resistors. This of course is approximate. Another approach is to use SpectreRF, as described in http://www.designers-guide.org/Analysis/sc-filters.pdf

-Ken

Title: Re: how to simulate fully differential amp with switch cap CMFB?
Post by alicia8283 on Dec 22^nd, 2008, 11:28pm

hi guys,

thanks a lot for the replies. As my company do not have the license for spectreRF :'( , so i unable to run the way according to the attachment.
Any other method? could you please specify more detail about the approximation method?

Thanks a lot