The Designer's Guide Community Forum

The Designer's Guide Community Forum
https://designers-guide.org/forum/YaBB.pl
Design >> Analog Design >> Pole zero plot
https://designers-guide.org/forum/YaBB.pl?num=1159169118

Message started by hande.vinayak on Sep 25^th, 2006, 12:25am

Title: Pole zero plot
Post by hande.vinayak on 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.
:-[

Title: Re: Pole zero plot
Post by packiaraj on 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.

Title: Re: Pole zero plot
Post by hande.vinayak on 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.

Title: Re: Pole zero plot
Post by semitao on Sep 27^th, 2006, 6:16pm

Hi,
Does anyone have any tutorial about spectre PZ & STB analysis?

best regards.

Title: Re: Pole zero plot
Post by Ken Kundert on Sep 27^th, 2006, 7:26pm

Background on STB: http://www.thekunderts.net/ken/docs/c%26d2001-01.pdf.

-Ken

Title: Re: Pole zero plot
Post by Andrew Beckett on 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.

Title: Re: Pole zero plot
Post by hchanda on 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

Title: Re: Pole zero plot
Post by Ken Kundert on Nov 2^nd, 2006, 7:52pm

The paper has been moved to http://www.kenkundert.com/docs/cd2001-01.pdf.