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Re: gEDA-user: Re: ideal op amps in gschem

H.S. wrote: 
Dan McMahill wrote:

H.S. wrote:


This might be a dumb question, how do I implement an ideal op amp in
gschem. I have to op-amps listed in analog section of components. Both
have five connections, of which two are of power supply. Could any one
explain how to use these or give a URL link that explains this?

I am using geda 20050820-1 on Debian Etch.

Thanks,
->HS



It is not clear what you are trying to achieve here.  Are you trying to
just have the typical 3 terminal op-amp one sees in books to draw some



Yes, this is the one I am trying to achieve. I am actually TAing a basic
electric circuits course and wanted to actually run simulations on small
schematics (HP or LP filters, voltage follower, differential amplifier,
etc.). So for these, I just a 3 terminal ideal amplifier. However, there
are some topics in the course in which I would need to actually specify
the input impedance, output impedance and gain explicitly to show how to
work with practical op amps. The idea is actually show the students the
curves relating output to the input.

I am only a beginner in using ngspice and geda. I can work with the
basic elemens (R,C,L and V/I sources) but haven't tried implementing op
amps yet. So all help is appreciated.

For very simple stuff it might not hurt to just introduce students to a netlist driven simulation. Sounds like what you're doing is simple enough that a netlist won't get out of hand and, speaking as one who makes heavy use of simulators professionally, you can never get away from needing to understand a netlist. Just yesterday in fact I spent some time looking at a netlist to understand what a GUI set up tool was really doing.

You might also take a look at gnucap. Its pretty easy to use, reads spice netlists, and can do things spice doesn't do.

If you do want to use gschem, you can just create a schematic for an ideal op-amp which consists of a high gain (you can pick how high is high enough) vcvs. The spice library for geda has a vcvs. Then I'd copy one of the op-amp symbols, open it up and remove the power pins to make a 3 terminal one.

-Dan