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Message started by analogue_guy on May 7th, 2009, 2:31pm

Title: Input impedance
Post by analogue_guy on May 7th, 2009, 2:31pm
Hi,

What kind of analysis and methodology are you using to simulate input impedance of non-linear circuitry?

Cheers,

--AG

Title: Re: Input impedance
Post by pancho_hideboo on May 8th, 2009, 11:35pm

analogue_guy wrote on May 7th, 2009, 2:31pm:
What kind of analysis and methodology are you using to simulate input impedance of non-linear circuitry?
It depends on your definition of an input impedance for non-linear circuitry.

Title: Re: Input impedance
Post by analogue_guy on May 11th, 2009, 12:26pm
Hi,

Basically let us say I have a circuit which input impedance varies with the input current and I would like to have the dependence of the input impedance of the input current.

How am I doing now? I basically apply an ipwl source and I sweep the current from 0 to the maximum level of interest and at some certain points I run ac simulations, collecting the data and from these data I calculate back the parallel RC equivalents.

i was interested in, if there is a better or easier way to do that?
or you can see any problem with that methodology

regards

Title: Re: Input impedance
Post by cmos.analogvala on May 11th, 2009, 7:24pm
I think this is the method. Two more things you can add in the existing simulation setup are 1) parametric simulations and 2) save expression in ADE if you are using cadence/Spectre. 1) Make dc value of your input current design variable. Vary that in parametric. 2) Use calculator to give you  Rin at some frequency and save the expression. The simulator will give you the plot of Rin vs parameter value.

CA

Title: Re: Input impedance
Post by analogue_guy on May 13th, 2009, 7:46am

cmos.analogvala wrote on May 11th, 2009, 7:24pm:
I think this is the method. Two more things you can add in the existing simulation setup are 1) parametric simulations and 2) save expression in ADE if you are using cadence/Spectre. 1) Make dc value of your input current design variable. Vary that in parametric. 2) Use calculator to give you  Rin at some frequency and save the expression. The simulator will give you the plot of Rin vs parameter value.

CA


Hi,

Thanks for your advices, it seems together with  DC sweep maybe I could use the captab option to extract the capacitance.

Cheers

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