On Monday 18 April 2005 10:46 pm, MSWaters wrote: > * I have derived an opamp model on which Ng-Spice can perform > an AC analysis. The model is based on the Maxim LMX358 model. > I haven't been able to find an opamp model on which GNU-Cap > can successfully perform an AC analysis. So far I've tried > models from National and Maxim.
It works for me. Even that LM358 model you supply works for me, after a simple change. That model looks strange to me. The real netlist would be simpler. It is amazing how much work some people will do to hide the real circuit. Here's a couple things to watch out for ,,,, In the old days, all Spice files reserved the first line for a comment, so the first line is ignored. Gnucap honors this, and drops the first line. For your LM358 model, I had to add a blank first line. If this isn't the way it is supposed to be, let me know. It is easy to change. All I need to do is take out that line of code that skips the first line. You may have forgot the "op" command. You must do an "op" analysis before doing an "ac" analysis, unless you want to simulate it with the power off. Actually, you can do anything first and Gnucap will use whatever it was at last as the operating point. This behavior is different from Spice, but is of great value in simulating nonlinear circuits in AC. Actually, for serious analog work, I have trouble making Spice do what I want.
