On Nov 10, 2010, at 4:09 PM, [email protected] wrote: > Hi Gang, > > I've been playing with ngspice and gnucap and have gotten good results with > the Non-Linerar Dependent Sources eg ASRC Bxxxx devices in ngspice. I mostly > use those with VC-Switches to make full wave bridges, SCRs, Triacs, etc...
Why not use the semiconductor models for semiconductor devices? Make full wave bridges from diodes, SCR's from cross-coupled transistors, etc. A great deal of effort has gone into accurately modeling semiconductor physics in these simulators: why not exploit it? A Google search for "spice scr model" turns up quite a few subcircuit models of this sort. If you can't find exactly the model you need, it's probably better to tweak one of these than make one up. > Though I see that they are not supported in gnucap. I guess the alternative > is to use POLYs. I've looked around and except for a short description in the > gnucap manual I haven't found a comprehensive howto on how to use them. A common way to go from data sheets to model parameters is to model test circuits and then tweak the parameters until there's a decent resemblance. > I sapose you would want a curve fitting program to help you generate the > coeficents like grace, or simfit, or you could use the fit function in > gnucap. However this isn't supported in ngspice, so you couldn't use that > model in both. You can configure ngspice to support POLY. See http://www.brorson.com/gEDA/SPICE/x496.html. > > Are POLYs really that much better at solving convergence problems to be worth > the extra trouble? Is there a good into or howto on how to use them? There is a vast literature on the subject of constructing polynomial approximations to functions. Google for "polynomial approximation". You'll never be able to digest it all. > Are negitive coeficents even legal? Sure, why not? John Doty Noqsi Aerospace, Ltd. http://www.noqsi.com/ [email protected] _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
