[Help-gnucap] Current source dependent on more voltages?

[Per Bull Holmen]

Hey

I'm a fairly experienced programmer, but TOTAL novice
regarding electronics, and not especially seasoned at
maths (yet pick up new subjects quickly). I want to
start a hobby project building a valve amplifier - and
need a simulator to simulate simple circuits. PSpice
and Spice valve models are plentyful on the net, but I
can't figure out how to turn them into gnucap models
(I've given up on PSPice/LTSpice/ngspice because of
bugs, evaluation limitations etc.). Norman Koren
calculates the current flowing from anode to cathode
in a vacuum tube like this (I have just replaced all
the constant parameters with a kN to show you the main
structure):

Ia = Vs/k1 * log( 1+exp( k1*((1/k2)+Vg/Vs) ) )^k3 *
2/k 4 * atan( Va/k5 )

Ia = current anode-cathode
Vs = screen voltage
Vg = grid voltage
Va = anode voltage

Here's the original:
http://www.normankoren.com/Audio/Tubemodspice_article.html

The point is that this current source is dependent on
three voltages. At first I thought I might try to use
the model compiler. But the docs don't answer the
question (at least to me): Can the evaluations in such
a model be dependent on more than one voltage? I'd
assume, for such a model, one would make an equation
that would calculate the current based on a vector of
voltages, and then let it calculate a vector of
partial derivatives of it? I would like to know if
this is doable before I start trying, cause I've spent
sooo long now trying to find a good simulator, been
frustrated several times and don't want to spend more
hours trying to program something that won't work...
:)

BTW, I'm using gnucap 0.35 cause it seems to be the
last stable release.



-- 

Mvh
Per Bull Holmen

"People demand freedom of speech as a compensation for the freedom of thought 
which they seldom use" - Søren Kierkegaard


      
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