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3DB bandwidth expression

Hi All,

I am trying to evaluate a function using the expression editor but am getting an error. This is for bandwidth of differential output divided by the differential input as shown below.

bandwidth(((VF("/vop") - VF("/von")) / (VF("/vip") - VF("/vin"))) 3 "low")

Will be helpful if someone can point the issue with using this expression to compute the 3db bandwidth. I have tried this expression both using AC & Tran analysis but nothing evaluates.

I am also need to use this expression in the MC analysis.

I am using IC618

Regards

Parents

Andrew Beckett over 3 years ago

Nothing obviously wrong with it. For me I just tried with a differential opamp example with:

bandwidth(((VF("/OUTN") - VF("/OUTP")) / (VF("/inn") - VF("/inp"))) 3 "low")

and it worked perfectly. Of course, it will only work with AC analysis (it makes no sense for transient analysis, because VF reads the results from ac analysis).

You say you are getting an error. It might help to tell us what the actual error is?

Andrew
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Andrew Beckett over 3 years ago

Nothing obviously wrong with it. For me I just tried with a differential opamp example with:

bandwidth(((VF("/OUTN") - VF("/OUTP")) / (VF("/inn") - VF("/inp"))) 3 "low")

and it worked perfectly. Of course, it will only work with AC analysis (it makes no sense for transient analysis, because VF reads the results from ac analysis).

You say you are getting an error. It might help to tell us what the actual error is?

Andrew
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sidm over 3 years ago in reply to Andrew Beckett

thank you very much for the reply Andrew, here the Spectre version is 18.1

I am seeing an error like the following in the CIW though I think when i plot the expression using the calculator it is getting plotted.
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Andrew Beckett over 3 years ago in reply to sidm

That's nothing to do with the expression you've shown above as it has VT() calls in it, and it seems to have VT("=") in it - so that's coming from somewhere else.

Andrew
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