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checking stability for a two stage fully differential simple OTA on cadence (Read 3119 times)

ahmedhany_94 New Member Offline Posts: 2	checking stability for a two stage fully differential simple OTA on cadence Jan 05^th, 2017, 8:26am I made this circuit for a two stage fully differential OTA I want to check its stability in a unity feedback but i have a version of cadence without the diffstbprobe
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deba

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Re: checking stability for a two stage fully differential simple OTA on cadence
Reply #1 - Jan 6^th, 2017, 12:37am

You can apply a small step input and look for the number of rings or overshoot in your output. Or

you can break the loop using a large inductor and capacitor, if you want to look at the open loop gain in frequency domain. Take care of loading while breaking the loop.

Thanks

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Andrew Beckett

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Re: checking stability for a two stage fully differential simple OTA on cadence
Reply #2 - Jan 6^th, 2017, 1:58am

If using an older version, you could use the older cmdmprobe component instead. This assumes that the two loops are balanced and that there's no significant CM to DM leakage (or vice versa), but is probably sufficient in this case.

Or you could use a more recent version. diffstbprobe has after all been there since IC614 (a hotfix of IC614 at least).

Regards,

Andrew.

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Frank Wiedmann Community Fellow Offline Posts: 677 Munich, Germany	Re: checking stability for a two stage fully differential simple OTA on cadence Reply #3 - Jan 10^th, 2017, 12:31am You can also build your own diffstbprobe, see http://www.designers-guide.org/Forum/YaBB.pl?num=1190707743 (Reply #1) and https://community.cadence.com/cadence_technology_forums/f/33/t/27989 (my last reply).
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