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hande.vinayak Junior Member Offline Posts: 22 BOM	Pole zero plot Sep 25^th, 2006, 12:25am Hello to all, I am designing a Folded OTA,please can anybody tell me how to plot a pole zero plot for finding a stability? I am working on Cadence Analog Design Environment tool. Thanks.
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packiaraj

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Re: Pole zero plot
Reply #1 - Sep 25^th, 2006, 3:55am

Why do you want to see the PZ plot to determine the stability? I feel Spectre's STB analysis is far better than PZ analysis to simulate stability margins. PZ analysis will give only the location of Poles and Zeros (a lot of them actually!!!) and NOT the parameters Like Phase Margin and Gain Margin. PM and GM are the impotant stability parameters as they would tell you how far is your circuit from becoming unstable.

Thanks,
Packiaraj.V.

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hande.vinayak Junior Member Offline Posts: 22 BOM	Re: Pole zero plot Reply #2 - Sep 25^th, 2006, 10:47pm Thanks, But as I am new this field,I wanted to know that while moving into the 'STB' anlysis.What we have to write into 'Probe Instance'----Block?I wanted to check open loop gain and open loop stability. Thanks. Vinayak.
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semitao Junior Member Offline Posts: 20	Re: Pole zero plot Reply #3 - Sep 27^th, 2006, 6:16pm Hi, � �Does anyone have any tutorial about spectre PZ & STB analysis? best regards. �
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Ken Kundert Global Moderator Offline Posts: 2384 Silicon Valley	Re: Pole zero plot Reply #4 - Sep 27^th, 2006, 7:26pm Background on STB: http://www.thekunderts.net/ken/docs/c%26d2001-01.pdf. -Ken
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Andrew Beckett

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Re: Pole zero plot
Reply #5 - Oct 28^th, 2006, 7:22am

I sometimes use pz analysis to figure out if the circuit is unstable - because you can tell this without having to analyse specific loops - it will analyse the whole circuit.

However, if you want to get information about the amount of margin, then stb is the man for the job. In addition to the reference that Ken posted, I believe there is an application note on http://sourcelink.cadence.com . If you can't find it, file a service request, and your friendly Cadence application engineer can locate it for you.

Regards,

Andrw.

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hchanda

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Re: Pole zero plot
Reply #6 - Nov 2^nd, 2006, 6:01pm

Hi ken,
I am looking for the document that talks about the spectre stability analysis. I was seaching for it in the forum
and found the pointer to document mentioned by you (please see below)
Background on STB: http://www.thekunderts.net/ken/docs/c%26d2001-01.pdf .

But I am not able find any document at that pointer. Could you please provide the pointer to document?

Thanks,
Hc

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hc

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Ken Kundert Global Moderator Offline Posts: 2384 Silicon Valley	Re: Pole zero plot Reply #7 - Nov 2^nd, 2006, 7:52pm The paper has been moved to http://www.kenkundert.com/docs/cd2001-01.pdf.
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