Re: gEDA-user: Phase and Magnitude of Current

[Yamazaki R2 <yamazakir2@xxxxxxxxx>]

So what do big name simulation front ends do when probing current,
does the simulator modify the netlist by sticking in a bunch of 0V
voltage sources? It would be good to know the proper method since im
currently in the middle of writing a front in for ngspice/gnucap to
replace gspiceui.

On Fri, Apr 10, 2009 at 1:15 PM, John Doty <jpd@xxxxxxxxx> wrote:
>
> On Apr 10, 2009, at 1:07 PM, Yamazaki R2 wrote:
>
>> Sorry to randomly jump in here, but in ngspice, the only way to probe
>> current is to probe a 0V voltage source? Theres no other work arounds
>> for this?
>
> It's classic SPICE technique.
>
>> For example, if I had a very large hierachical design with
>> 10,000 transistors in it and I wanted to plot the drain current of one
>> particular transistor, I'd have to either edit the schematics and
>> break apart the net and insert a 0V voltage source or hack the
>> netlist?
>
> Hardly difficult. The most important thing any professional needs to
> learn is not to get stuck on a trivial impediment.
>
>> Isnt that a pretty important missing feautre? Gnucap lets you
>> probe device currents without hacking the schematics.
>
> Gnucap is a rapidly advancing work in progress. SPICE is
> conservative, stagnant, but still much more important. There's
> enormous knowledge and experience available for SPICE, little for
> gnucap. I expect gnucap will eventually surpass SPICE in all areas,
> but it isn't there yet.
>
>>
>> On Fri, Apr 10, 2009 at 11:33 AM, John Doty <jpd@xxxxxxxxx> wrote:
>>>
>>> On Apr 10, 2009, at 12:19 PM, awchang2@xxxxxxxxxxx wrote:
>>>
>>>> So spice won't actually calculate the current for me?
>>>
>>> In this particular case, you can also use Ohm's law to convert
>>> voltage to current through the resistors, and KCL to get the reactive
>>> currents versus time from your transient simulation. Of course, you
>>> could also just do it entirely by hand from the complex impedances at
>>> a given frequency. Spice is a little excessive here.
>>>
>>> Lots of ways to do this problem. You want to get good at this? Master
>>> them all..
>>>
>>> John Doty              Noqsi Aerospace, Ltd.
>>> http://www.noqsi.com/
>>> jpd@xxxxxxxxx
>>>
>>>
>>>
>>>
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>>
>>
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>
> John Doty              Noqsi Aerospace, Ltd.
> http://www.noqsi.com/
> jpd@xxxxxxxxx
>
>
>
>
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