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ymin() returns unexpected error for a waveform family

ZoltanT

Hi Everyone,

I can not get the minimum value of a waveform family. I would expect that ymin returns a waveform where the Y values are minimum y values of the waveforms in the waveform family and the X values are the leaf values of the family. ymin returns with the error below for a family. I am able to plot the waveform family. ymin() work well for a different waveform family created by IS() function from a parametric DC sweep.

expression evaluation failed: Expression evaluates to nil
expression evaluation failed: ymin(-IF("/VD/PLUS"))

I created a simple procedure to check whether something is wrong with processing the family with a function, and it worked well. See code below. I am clueless how to debug the issue and generate the waveform, what I wanted to see, and which would help me make better decisions in the circuit design.

procedure( example(x)
   x+1
)
example(-ID("/VD/PLUS"))

Clearly there is something I do not notice or do not understand about using the function. Could you tell me how to debug it further and help me understand what's going on? Why is one waveform family accepted, but the other not.

Regards,
Zoltan

Edit: I use icadv 12.2-64b.500.7

Parents

  • Hi Zoltan,

    The issue is probably because IF returns the results from an AC analysis, which means that the results are a complex current (from this you can find the magnitude and phase, or real and imaginary parts). The ymin function cannot find the minimum complex value (what would that mean, for a start?).

    So I suspect you just need to do:

    ymin(-mag(IF("/VD/PLUS")))

    Regards,

    Andrew.

  • in reply to Andrew Beckett

    I would have bet, that I have checked it.. This was the problem. Thanks.

    To answer your rhetorical question I do not find it illogical to assume that the magnitude is used in every calculations just as the magnitude is plotted for a complex waveform. It seems to me rather intuitive to return the smallest Y-axis value of a plot for the ymax() function. Anyway, I see the logic behind it. I just wish that the error message would have given a more useful message.

  • in reply to ZoltanT

    I completely agree with you. There's an enhancement CCR asking for mag to be applied when using these functions with complex data - CCR 1636329.

    This has come up so many times that I ended up writing an article a while back about why it returns nil: ymin and ymax sometimes return nil. Why?

    Andrew.

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