Re: gEDA-user: Why the current is negative(of ngspice)?

[Dan McMahill <dan@xxxxxxxxxxxx>]

Yang Hawk wrote:
>  have a question about why my current flow is negative:
> my circuit net list here:
> diode
> vs    1    0    dc    1v
> d1    1    0    dnorm
> .dc    vs    -0.8v    0.7v    0.004v
> .model    dnorm    d(is=1e-14)
> .probe
> .end
> 
> and in ngspice, I execute,
> plot i(vs)
> 
> the plot graph is shown that the current is negative
> 
> I find the answer from ngspice/spice3f5 user's manual:
> I(VXXXXXXX)
> 
> specifies the current flowing in the independent voltage source named 
> VXXXXXXX. Positive current flows from the positive node, through the 
> source, to the negative node. For the ac analysis, the corresponding 
> replacements for the letter I may be made in the same way as described 
> for voltage outputs.
> 
> 
> so, no doubt, the current is negative. But why the spice is so designed?
 >

why not?

> and How could I check current between any two nodes?

I'm assuming you mean "how could I check current in any branch".  You 
can insert a zero volt DC voltage source in any branch and monitor the 
current through it.


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