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Stability analysis for two stage CMOS Op Amp in Spectre (Read 794 times)

RobertZ Community Member Offline the art of analog Posts: 55 San Diego, CA	Re: Stability analysis for two stage CMOS Op Amp in Spectre Reply #15 - Jun 19^th, 2009, 12:03am Frank Wiedmann wrote on Jun 18^th, 2009, 11:48pm: Yes, I think this is right. but how can you tell there are two RHP poles in open loop gain from his bode plot? Thanks, Robert
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RobertZ Community Member Offline the art of analog Posts: 55 San Diego, CA	Re: Stability analysis for two stage CMOS Op Amp in Spectre Reply #16 - Jun 19^th, 2009, 12:07am Frank, btw, can you take a look at my another post: http://www.designers-guide.org/Forum/YaBB.pl?num=1245305413 maybe you have some clue. Thanks, Robert
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Frank Wiedmann

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Munich, Germany

Re: Stability analysis for two stage CMOS Op Amp in Spectre
Reply #17 - Jun 19^th, 2009, 4:37am

RobertZ wrote on Jun 19^th, 2009, 12:03am:

but how can you tell there are two RHP poles in open loop gain from his bode plot?

Thanks,
Robert

Assume that you have an open loop gain function T(s)=A/[(s-p1)*(s-p2)] with two RHP poles at p1=2π*10³ 1/s and p2=2π*10⁶ 1/s. Do a Bode plot of this function for s=j2πf. What do you get?

« Last Edit: Jun 19^th, 2009, 5:40am by Frank Wiedmann »

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RobertZ Community Member Offline the art of analog Posts: 55 San Diego, CA	Re: Stability analysis for two stage CMOS Op Amp in Spectre Reply #18 - Jun 19^th, 2009, 9:55am you are right. there are 2 poles in RHP, other thatn that, there is a LHP zero, which is close to the 2nd pole, and a RHP zero after unitiy gain bandwidth.
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