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Simulators >> Circuit Simulators >> Terminal Flip for reverse mode
https://designers-guide.org/forum/YaBB.pl?num=1417424228

Message started by Gabor on Dec 1^st, 2014, 12:57am

Title: Terminal Flip for reverse mode
Post by Gabor on Dec 1^st, 2014, 12:57am

Hello,

in some Papers I have read, that in Cadence, the simulator is simply doing a terminal flip for transistors when V_ds becomes negative, thus only right sided differentiation of I_ds is done for higher orders. Where can I find authoritative information about this behavior?

Thank you

Title: Re: Terminal Flip for reverse mode
Post by Geoffrey_Coram on Jan 5^th, 2015, 1:10pm

You can look at the BSIM3/4 source code at UC Berkeley; you'll see that the equations are only defined for Vds >= 0 (and for NMOS), and the appropriate swapping is done in the other cases.

But I don't know what you mean by "only right sided differentiation." The derivatives are computed symbolically -- it's not that one needs the value at a negative Vds in order to compute a numerical derivative.

Title: Re: Terminal Flip for reverse mode
Post by Gabor on Mar 9^th, 2015, 2:49am

Thank you very much for your answer.

Yes, exactly that is what I am looking for: the appropriate swapping in the other cases. Where is it done? Directly in the Simulator? I could not find an literature.

(With right-sided Differentiation I mean, that the symbolic differetntiation is done before the "swapping" and without 0, since no value exists there after the second derivative)

Thank you.

Title: Re: Terminal Flip for reverse mode
Post by Frank Wiedmann on Mar 9^th, 2015, 8:18am

You might want to take a look at http://www.designers-guide.org/Forum/YaBB.pl?num=1359061621.

Title: Re: Terminal Flip for reverse mode
Post by Gabor on Mar 10^th, 2015, 12:37am

Dear Frank,

thank you for the hint.

I actually understand the mechanism of the IM3 failure existent by threshold voltage based models. I am also aware of the effect of switches. I am working on a Workaround, and I would like to find a proper source to decently do the referencing for some derivations for publication.

Yet, although the situation is actually clear and Logical, I can only find hearsay about the "terminal flip" or "swap", no referencable written literature that says where and how exactly it is done. Thus, yet, I can only refer to it as "it is gererally known".

Title: Re: Terminal Flip for reverse mode
Post by Frank Wiedmann on Mar 10^th, 2015, 1:48am

How about http://www.researchgate.net/publication/3075044_Validation_of_MOSFET_model_SourceDrain_Symmetry ?