Re: gEDA-user: Problem with 2N3906 model in gnucap

[al davis <ad151@xxxxxxxxxxxxxxxx>]

On Tuesday 05 February 2008, Robert Butts wrote:
> I downloaded the model from fairchild's website.  I'm
> simulating this very simple circuit in gnucap and am getting
> the following error:
>
> -------------------------------------------------------------
> DUAL AMP CIRCUIT
> ... f                Ne=1.536 Ikf=.3287 Nk=.9957 Xtb=1.5 Var
>                                         ^ ? what's this?

(the arrow points to "Nk") ...  
The "PNP" (BJT) model does not accept the parameter "Nk".

based on a comment .....
>>created using Parts version 6.0 on 11/19/01 at 16:43
>>* Parts is a MicroSim product
That tells me that the model is specifically for PSpice, and not 
designed for any other simulator.

I checked the plugins (for the development version) and none of 
them support the Nk parameter either, which tells me that 
NGspice doesn't support it.  (The NGspice models can be used 
with gnucap as plugins).

My recommendation is to remove that parameter and try again.

In general, if a device model uses a parameter that is not 
supported, you can usually get satisfactory results by omitting 
that parameter.

I assume you are aware that those model parameters need to be 
taken with a bit of suspicion.  For example, the NPN gives 
a "Bf" value (forward beta) of 416.4.   For real transistors 
this parameter varies widely.  Any number from 200 to 500 would 
be believable, and they do vary this much in production.  Other 
parameters vary like this too.  I just picked this one because 
the beta of a transistor is well understood.

> print ac v(2) v(computerMic)
>                 ^ ? no match

(the arrow points to "computerMic")

There is no "computerMic" in your netlist.


I see some other errors too ...

You ask for an AC analysis but don't have any AC sources.  
The "SIN" source is for transient analysis.  You need to give 
an AC value.

You don't have a power supply.  I see nodes "Vcc" and "-Vcc", 
but those are just node names.  You need sources.

You asked for an AC analysis without a preceding "op" analysis.  
This corresponds to asking for an analysis with the power off.

Starting a node name with "-" is not recommended.  Sometimes it 
leads to surprises.  It is also not a good idea to have a node 
name the same as an element name.  Again, strictly it is legal, 
but sometimes leads to surprises.


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