On Wednesday 09 July 2008, Johannes Bauer wrote: > Now I wanted to use a diode, for example. However I have to > specify a model as a value - now one really silly question > is: How do I find out what models are available for diodes? I > tried some standard values like 1N4001 and 1N914 none of > which were recognized.
If you need to ask that question, you probably can get by with just guessing. Just make a model statement taking the defaults: .model 1n4001 d If you need a little more accuracy than that, adjust the parameter IS to get the expected forward voltage. As you get more advanced, you can look on the web for specific models. Google for "1n4001 spice model" and see what you find. It should ultimately lead you to something of the form: .model 1N4001 D (and a bunch of name-value pairs) You could just use that, but if you want that kind of detail you should look at several to see how much they vary. Usually, most Spice models work with gnucap, but it cannot be guraranteed. There are so many devices, from so many vendors, that it is impossible to keep track of them all. > Is there also a way to use operational amplifiers? I'd guess > that would be the "U: Logic Device" family in analog mode, > but again - the problem with knowing which models are > supported. Tried the LM324, but no luck again. No .. the "U" is not an op-amp. Op-amps are more complex devices, so you need to decide what kind of model you want. If you need to ask, you can probably get by with a very simple model. Use a voltage controlled voltage source (VCVS, type E). Eop (out1 0 in+ in-) 10000 If you need to model clipping, use the "tanh" behavioral modeling function to specify open loop gain and clip voltage. Eop (out1 0 in+ in1) tanh(10000, 12) If you need something a little better, make a subckt with two controlled sources and a dominant pole. If you don't know how to do this, the VCVS is probably all you need. If you need better, google for a spice model. (or in the future .. Verilog-A model) .. Op-amp models are usually subcircuits, designed for a particular variant of Spice. Some work, some don't. The only way to know is to try it. These models have lots more detail. If you are just beginning, you are better off without it. _______________________________________________ Help-gnucap mailing list [email protected] http://lists.gnu.org/mailman/listinfo/help-gnucap
