On Sunday 07 December 2008, vsrk sarma wrote: > I am facing difficulties in including device/sub-circuit > models into gnucap simulation. > Specifically for transistors & analog ICs such as opamps. > It appears to me that application package does not have any > and we have to create. Am I right?
Models for specific devices are not included. You need to "Google for it", or make your own. > Is it possible to use available spice models? If so how to > make them compatible with gnucap. > how to ensure pin compatibility of imported model & my > circuit. Gnucap mostly accepts spice models. The reason I say "mostly" is that there is so much variation in Spice models. Is a model written for HSpice? PSpice? Each one is a little different. You need to try it. The one closest to gnucap is HSpice. The development snapshot has more features, so if you get a model that is not compatible with gnucap-0.35, it is likely it will work with the development snapshot. Pin compatibility is not an issue. Gnucap uses the same syntax and pin lists as Spice. If you are using J-Fets, you must use the development snapshot. > Apologies for very basic questions (I have not used Spice > earlier ) If you are just getting started, it is usually better to make your own models. You probably don't need the detail provided by the published models. You will benefit if you understand the models you use. For an op-amp, you can usually use a voltage controlled voltage source. For transistors, usually you can just add a ".model" statement, and specify "BF" (beta) and "IS" (saturation current). For MOSFETS you can usually specify "level=1" for the simplest model and specify "VTO" (threshold voltage) and "KP" (transconductance parameter). You need to know this to design your circuit anyway. Sometimes you need to experiment with the parameters. Here's a reference that might help with that: http://wiki.gnucap.org/dokuwiki/doku.php?id=gnucap:experimentally_finding_model_parameters Everything I said here applies equally to Spice. The models are the same. _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
