virtuoso -problem while plotting current density with vgs sweep

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prabhjot_devgun

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Hi everyone,

I am trying to plot current density (Id/Weff) v/s Vgs i.e Vgs sweep, but unable to plot and get following error in CIW (IC616 virtuoso):-
expression evaluation failed: val is not legal.
expression evaluation failed: OPT("/M0","ids")/OPT("/M0","weff")
"("quotient" 0 t nil ("*Error* quotient: can't handle (srrWave:0x23af1020 / nil)"))"
Click to expand...

I tried to make expression in calculator using opt option and used ids/Weff. I have added the screenshot. Please help me to solve this problem.

Regards.
 
Last edited by a moderator:

Can't find a screenshot.

Seems weff can't be found. Are you sure that weff is a parameter which can be found in the parameter set of transistor M0 ? If not, you'd have to declare it explicitly as a parameter.
 
What if you substitute the -value- of Weff that you know
to be true, or that you can pick out of model / OP result
by a preceding calculator expression?
 
Thank you all of you for quick reply. sorry i forgot to attach screen shot. Actually i am working on gm/id method.



please point out where am i making mistake.

Regards.

- - - Updated - - -

Thank you for quick response. i need to plot id/(Weff) v/s gm/id OR id/(Weff/Leff) vs Vgs for this i used parametric sweep of Vgs. and tried to plot current density using calculator as shown in pic. please guide me how to plot it.



Regards.
 

@Dominik Przyborowski, thank you for your response. you are right , i made mistake. So please tell me how to do this plot. i use 6.16 version of virtuoso. I am totally confused.
 

In such cases, I usually use result browser tool. From it you can easily export parameters, for example I've tried to calculate your expression for transistor N3:

Code: 
pv("N3" "ids" ?result "dcOpInfo")/pv("N3" "w" ?result "instance")

But I'm not sure that "w" parameter returns Weff (anyway it's not width from parameters of transistor, in my case w = 2.4u, "w" parameter returns 2.16u).
 
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