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unable to plot dB20

Charanraj Mohan

Hi,

I am doing a common mode voltage AC analysis of a 2 stage OPAMP. When I plot the AC phase and magnitude, i get the following error.

Unable to plot expression <dB20((VF("/out") / VF("/in1")))>

because it does not evaluate to an object that can be plotted, like a waveform or

parametric wave. See the Visualization & Analysis Tool documentation for information

about the types of objects that can be plotted in Visualization & Analysis Tool. Only

the expressions that evaluate to those objects can be plotted.

*Warning* Wave11 is not a waveform object that can be displayed and

will be DELETED automatically.

name: "dB20(VF(\"/out\")/VF(\"/in1\"))"

I also get this error in red color in the beginning -

*Error* Evaluating expression (dB20((VF("/out") / VF("/in1"))))

*Error* ("eval" 0 t nil ("*Error* eval: unbound variable" gridResol))

But I am getting the phase plot and it is reasonably ok. How to overcome this error ? I click the output and the one of the inputs.

thanks in advance.

Parents

  • This might just be because of the extra unnecessary parentheses you have in the expression. SKILL has a problem if you use more than one set of matching parentheses as it confuses the parser (which can handle C-like and LISP-like expressions). So try changing to:

    dB20(VF("/out") / VF("/in1"))

    and see if that helps. I am (of course) assuming you've saved the signals involved in the expression - judging by the fact that you can plot the phase (you didn't give the expression for that) I would imagine you've done that.

    Regards,

    Andrew.

Reply

  • This might just be because of the extra unnecessary parentheses you have in the expression. SKILL has a problem if you use more than one set of matching parentheses as it confuses the parser (which can handle C-like and LISP-like expressions). So try changing to:

    dB20(VF("/out") / VF("/in1"))

    and see if that helps. I am (of course) assuming you've saved the signals involved in the expression - judging by the fact that you can plot the phase (you didn't give the expression for that) I would imagine you've done that.

    Regards,

    Andrew.

Children
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