Re: gEDA-user: Newbie wondering about simulation

[John Doty <jpd@xxxxxxxxx>]

On Oct 24, 2010, at 6:29 AM, Hannu Vuolasaho wrote:

>   Hello!
>   I'm newbie with simulaition and I thought I was able to defeat this
>   problem but its ghost still walks with me. The next design is too big
>   to be calculated reasonably with paper, pen and TI-85.
>   First the versions: gschem 1.6.1.20100214 ngspice-20 : Circuit level
>   simulation program
>   These are from Arch linux' AUR and packages.
>   In my second simulation ever I downloaded spice files from IRF. Then I
>   put one FET to my design and tried to simulate.
>   As I discovered the FET had to be X1 because it is subcircuit. Howevere
>   gnetlist -g spice-sdb generates it as MX1 which doesn't work. ngspice
>   says it can't find model.
>   So what I'm doing wrong? Changing manually to X1 makes the simulation
>   work but it isn't really the Solution.

The spice-sdb back end tries to figure out what the correct SPICE prefix is and "repair" it for you. You can turn this feature off with the --nomunge flag ("gnetlist -g spice-sdb --nomunge"), or you can change your device= attribute to something it doesn't recognize.

> I've copied below parts of sch
>   and net file.
>   I'm curious about the last line in net file. It says M1. Is it version
>   of model name of something or what? The ideal PMOSFET used in creating
>   the IRF FET which acts like real device?

It's a four terminal (drain, gate, source, substrate) internal FET. I presume the part you clipped has the package parasitics in it.

>   Thanks in adance
>   Hannu Vuolasaho
>   From sch file the FET is declared as:
>   C 49200 45800 1 0 0 pmos-3.sym
>   {
>   T 49800 46300 5 10 0 0 0 0 1
>   device=PMOS_TRANSISTOR
>   T 49900 46400 5 10 1 1 0 0 1
>   refdes=X1
>   T 49200 45800 5 10 0 1 0 0 1
>   file=./spice/irf7410.spi
>   T 49200 45800 5 10 1 1 0 0 1
>   value=irf7410
>   T 49200 45800 5 10 0 1 0 0 1
>   model-name=irf7410
>   }
>   and net file:
>   *********************************************************
>   * Spice file generated by gnetlist                      *
>   * spice-sdb version 4.28.2007 by SDB --                 *
>   * provides advanced spice netlisting capability.        *
>   * Documentation at http://www.brorson.com/gEDA/SPICE/   *
>   *********************************************************
>   *vvvvvvvv  Included SPICE model from ./spice/irf7410.spi vvvvvvvv
>   .SUBCKT irf7410 1 2 3
>   **************************************
>   *      Model Generated by MODPEX     *
>   *Copyright(c) Symmetry Design Systems*
>   *         All Rights Reserved        *
>   *    UNPUBLISHED LICENSED SOFTWARE   *
>   *   Contains Proprietary Information *
>   *      Which is The Property of      *
>   *     SYMMETRY OR ITS LICENSORS      *
>   *Commercial Use or Resale Restricted *
>   *   by Symmetry License Agreement    *
>   **************************************
>   * Model generated on Jan 27, 03
>   * MODEL FORMAT: SPICE3
>   * Symmetry POWER MOS Model (Version 1.0)
>   * External Node Designations
>   * Node 1 -> Drain
>   * Node 2 -> Gate
>   * Node 3 -> Source
>   M1 9 7 8 8 MM L=100u W=100u
>   .MODEL MM PMOS LEVEL=1 IS=1e-32
>   CLIP CLIP CLIP
>   *^^^^^^^^  End of included SPICE model from ./spice/irf7410.spi
>   ^^^^^^^^
>   *
>   *==============  Begin SPICE netlist of main design ============
>   R3 1 2 1k
>   MX1 n1 2 0 irf7410
>   V2 1 0 pulse 0 10 10n 10n 100n 500n 3u
>   V1 n0 0 pulse 0 10 10n 10n 100n 1u 2u
>   R1 n1 0 1k
>   C1 n0 n1 3.3nF
>   .end
> 
> 
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John Doty              Noqsi Aerospace, Ltd.
http://www.noqsi.com/
jpd@xxxxxxxxx




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