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Design >> Analog Design >> simulation opa question
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Message started by chungmnig on Jun 20^th, 2006, 8:38pm

Title: simulation opa question
Post by chungmnig on Jun 20^th, 2006, 8:38pm

Hi~~
when we design a SC-CMFB based opa often use PSS & PAC to analysis it gain & phase Margin.
But when i take off the CMFB the phase Margin is smaller .

My question is : when we use SC-CMFB ,the simulation is only care PAC & PSS , can neglect ac analysis ?
thanks~~~!!!

Title: Re: simulation opa question
Post by ywguo on Jun 21^st, 2006, 6:11pm

Chungmnig,

How do you keep it to operate at right DC poing if you take off the CMFB?

BG
Yawei

Title: Re: simulation opa question
Post by chungmnig on Jun 21^st, 2006, 10:32pm

ywguo wrote on Jun 21^st, 2006, 6:11pm:

Chungmnig,

How do you keep it to operate at right DC poing if you take off the CMFB?

BG
Yawei

i take off CMFB and directly connect vcmfb to the opa node.

Title: Re: simulation opa question
Post by ywguo on Jun 22^nd, 2006, 10:04pm

Chungmnig,

The opa must not work if you put it in an open-loop when it is of high gain, although you try to connect vcmfb to opa node directly.

Best regards,
Yawei