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Date: Mon, 17 Nov 2014 12:56:35 +0300
From: Vladimir Zhbanov <vzhbanov AT gmail DOT com>
To: geda-help AT delorie DOT com
Subject: Re: [geda-help] newbie: automatic way to find a model
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On Thu, Oct 30, 2014 at 12:05:15AM +1100, Jack Andrews wrote:
>    Hi,
>    My interest is
>     - bread-boarding some hardware ideas
>     - saving time messing with hardware by using simulation
>    So I ended up looking at [ng]spice and gschem
>    This is my first day and I'm quite pleased with my progress - all
>    credit due to gEDA.
>    I drew up the start of a current mirror in gschem and
>    $ gnetlist -v -g spice-sdb current-mirror   #see current mirror in
>    shell script below
>    and the body of the output was:
>    B2 5 7 0V
>    R4 1 unconnected_pin-1 7 5K
>    B1 7 6 12V
>    Q1 2 2 6 unknown
>    Q2 4 2 6 unknown
>    R3 3 5 5K
>    R2 4 3 10K
>    R1 2 1 10K
>    .end
>    In my schematic, I specified Q{1,2} as 2N2222 - but to run ngspice, I
>    seem to need to find the model for 2N2222.  I'm sure the question has
>    been asked before:
>      . is there an automated way to find the model for 2N2222?
Probably spicelib could help you. Please read [1] and search for the
link there.

>    If this is currently done manually, I'd like to contribute some work.
>    (I'm in software by day).
>    Also, note the R4 VARIABLE_RESISTOR is being used as a variable
>    resistor (not a potentiometer) so there is a floating node.  What is
>    the best way of drawing what I want?  And then, how do I get spice to
>    vary the resistor in 33 steps?  Maybe use a VCR
>    voltage-controlled-resistor and vary the voltage control?  Starting to
>    get vague now...
I think you ought to read the "Parameter sweep" section in the ngspice
manual. For your resistor you can make a subschematic with two resistors
in it.

HTH,
  Vladimir

[1] http://wiki.geda-project.org/geda:ngspice_and_gschem