On Thursday 04 September 2008, Gary L. Roach wrote: > I have just read through Stewart Brorsan's Circuit simulation > using gEDA and SPICE -- HOWTO. I am really confused about how > one is supposed to add parameters to components. Strings of > hieroglyphics after the model parameter doesn't help. Is > there any concise treatise that explains all of the spice > parameters and their uses.
I thnk what you are asking about is how to specify model parameters and the like. In my experience, usually I need to manually edit the generated netlist. Also, I never put simulation commands in the schematic. Instead I run the simulator interactively or make a separate script. In the schematic, you need a "value" attribute, which is passed to the simulator as is, without checking. As to figuring out the "strings of hieroglyphics", you need to understand the parameters of the individual models you are using. There are hundreds of these models, all with different parameters. These models come from a variety of sources, each separately documented. Some of these documents are hundreds of pages long. By "models" here, I refer to the code describing the equations and their parameters, not the ".model" (dot-model) statements used by spice and its derivatives. Mostly, the parameters are supplied by the fab. If you are doing simple circuits, it is best to use the simple models, and supply just a few parameters that you can determine, such as beta of transistors. Then leave the rest to their default values. Unfortunately, teachers often don't teach it this way. They tell you to just use overly complex models, which don't necessarily match to anything. Some commercial demo simulators come with parameters for common parts, often bogus or not representative of the spread of real devices. The teachers tell you to use them without any understanding of what they are about, or what to do when what is there doesn't match what you need. They are doing a lot of damage. Sometimes I think they are as clueless as you are. I know I didn't answer your question. There is too much there. Hopefully, I gave you some background that may help understand why there is a problem. If you can be more specific, perhaps I can really answer it. _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
