Re: [ng-spice-devel] a useful device
On Thu, 22 Feb 2001, mcmahill@mtl.mit.edu wrote:
> you know what would be useful to have? A voltage source like
> device which you could specify to only be present for an operating
> point analysis. The application is where you want to have
> something connected to get a circuit biased correctly and then
> vanish during an AC analysis. I often times just use a very large
> inductor, but it might be nice to actually have a device for this.
ACS has that, close enough to do what you want.
As you know, Spice lets you give AC, DC, tran values for sources.
So, you can give a DC value, and it becomes like a short for AC.
What you want is for it to become an open for AC, not a short. In
ACS, all passive components can have separate AC, DC, etc.. values,
so use a resistor. Give it a low value for DC and a high value for
AC.
R123 (1 2) dc 1 ac 1g
Another thing that ACS lets you do is to run a transient analysis to
a point, then stop it and do an AC analysis there. I have used this
in analyzing audio amps in the frequency domain at various points on
the waveform.
al.
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