Re: gEDA-user: Spice Question

[Shahab Sanjari <sanjari@xxxxxxxxxxxxxxxxxxx>]

Most of the opamp models available on the internet are in spice2 format.
Spice3 offers more flexibility for definition of non linear dependent 
sources than the POLY statement in spice2. I don't know any tool that can do
the conversion but you can do it manually.

F1 9 98 POLY(1) VA3 0 0 0 1.0985E7

The above line means you have a current controlled current source connected
with positive node 9 and negative node 98. The polynomial dimension is one, so you could
even omit it from the above line because it is the default.
The controlling current flows through the voltage source "VA3".
you have 4 polynomial coefficients:

P0 = 0
P1 = 0
P2 = 0
P3 = 1.0985E7

this means your final polynomial is:

I = 0 + 0 * I(VA3) + 0 * (I(VA3)^2) + 1.0985E7 * (I(VA3)^3)

which is simply:

I = 1.0985E7 * (I(VA3)^3)

the final line becomes:

B1 9 98 I = 1.0985E7 * (I(VA3)^3)


you can read more in the SPICE3 users manual for example from the appendix C of:

http://newton.ex.ac.uk/teaching/CDHW/Electronics2/userguide/

hope this helps.

regards,
Shahab.


On 22:54 Fri 12 Aug     , User Tomdean wrote:
> 
> Sorry for the somwhat off subject question.
> 
> I am trying to convert some opamp models to spice3 format.  I believe
> they are in spice2 format because of the poly() statement.
> 
> The models in question are for the lf353.  The statements are:
> 
> *
> ***********COMMON MODE EFFECT***********
> *
> I2 99 50 1.7MA
> *^Quiescent supply current
> EOS 7 1 POLY(1) 16 49 5E-3 1
> 
> Where EOS can be replaced by
> BOS 7 1 V=5e-3+v(16,49)
> 
> Now, the problem.
> *
> **************SECOND STAGE**************
> *
> EH 99 98 99 49 1
> F1 9 98 POLY(1) VA3 0 0 0 1.0985E7
> 
> What is the syntax to replace F1.  Playing with the lm741, I found
>    F6 50 99 POLY(1) V6 450U 1
> which may be replaced by
>    B6 50 99 I=450e-6+I(V6)
> 
> How do I replace the 
> 
>    F1 9 98 POLY(1) VA3 0 0 0 1.0985E7
> 
> >From poly(1), I think the last term,1.0985E7  is an initial value.
> What is the polynomial?
>     
> How do I convert this to a spice3 nonlinear source, like
> 
> B1 9 98 I=???????
> 
> tomdean

-- 

Shahab Sanjari  (sanjariathrzdottu-darmstadtdotde)