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Date:	Mon, 29 Oct 2012 23:12:12 +0400
From:	Vladimir Zhbanov <vzhbanov AT gmail DOT com>
To:	geda-help AT delorie DOT com
Subject:	Re: [geda-help] Another new user question on ngspice- how to export
	plots, and using current
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On Sat, Oct 27, 2012 at 07:51:55PM -0700, keitho AT strucktower DOT com wrote:
> Hi all-
> 
> I'm using ngspice on Linux/Debian. I guess the graphing/plots are done
> using X11 by default? I haven't figured out how to export my graphs to
> PNG's so that I can send them in emails to folks helping me learn. Is
> there a way to do that, or do you recommend using a different program for
> graphing the plots that provides that feature?

I'd suggest you to try out gnuplot or pyxplot.

> 
> Second question: in general, I'm confused about the way ngspice handles
> current. Just as an example, here's a trivial netlist of a circuit using a
> current source to drive the base:
> 
> common-emitter amplifier
> i1 0 1 dc
> q1 2 1 0 mod1
> r 3 2 5000
> v1 3 0 dc 15
> .model mod1 npn
> .control
> dc i1 0 50u 2u
> run
> plot v(2)
> .endc
> .end
> 
> Here's the output of display:
> 
> ngspice 2 -> display
> Here are the vectors currently active:
> 
> Title: common-emitter amplifier
> Name: dc1 (DC transfer characteristic)
> Date: Sat Oct 27 22:39:55  2012
> 
>     V(1)                : voltage, real, 26 long
>     V(2)                : voltage, real, 26 long
>     V(3)                : voltage, real, 26 long
>     i-sweep             : voltage, real, 26 long [default scale]
>     v1#branch           : current, real, 26 long
> 
> 
> The graph of this is the correct shape, but I'm confused about why it is
> sweeping voltage rather than current. Can someone explain what's going on
> here, or point to a tutorial that would help?

Looks like a bug in ngspice. You'd better ask this in one of ngspice
mailing lists (you can find their addresses at
http://ngspice.sourceforge.net/faq.html). Or try to use gnucap and
compare results. There are some differences between the two programs in
the netlist format they're using. Be prepared.

-- 
http://vzhbanov.byethost33.com

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