On Thursday 15 May 2008, Mark Lorenz wrote: > >You've not added a diode model. Thus a simple diode model is > > used. > > Where can I find some instructions on obtaining and adding > new models?
As you probably already figured out, you need "model" statement to parameterize the diode ... D2 (a k) 1n4004 Now you need a model statement ... .model 1n4004 d (a whole bunch of parameters) You could do a web search for a detailed model, but usually you can just do some experimenting.. If you are at the stage where you are asking about this, the detail will only confuse you, most likely of the worst kind of confusion, where you don't realize it. Most of the time, the only parameter you need for a diode is saturation current, which of course isn't in the data sheet. ok .. so how do I figure that out?? Well ... Look at the specs, or measure it. Let's say we found that the forward voltage at 1 amp is .7 volts. Use the simulator to build a test circuit .. I1 (0 1) dc 1 D1 (1 0) my_diode You need a model statement .. .model my_diode d (is=something) but I don't know what the value of something is. With gnucap .. try this....... gnucap> build >i1 (0 1) dc 1 >d1 (1 0) my_diode >.model my_diode d is=something > ******** blank line to exit build mode gnucap> probe op v(1) parameter something has no value gnucap> op # v(1) 27. 0.83376 **** using default IS gnucap> param something=1u gnucap> op # v(1) 27. 0.35733 gnucap> param something=1n gnucap> op # v(1) 27. 0.53599 gnucap> param something=1p gnucap> op # v(1) 27. 0.71465 gnucap> param something=2p gnucap> op # v(1) 27. 0.69673 gnucap> param something=1.5p gnucap> op # v(1) 27. 0.70417 gnucap> param something=1.8p gnucap> op # v(1) 27. 0.69945 gnucap> param something=1.7p gnucap> op # v(1) 27. 0.70093 gnucap> param something=1.75p gnucap> op # v(1) 27. 0.70018 gnucap> exit There .. close enough ,,, Now use the value 1.75p for IS. Here's your model statement: .model my_diode d is=1.75p _______________________________________________ geda-user mailing list [email protected] http://www.seul.org/cgi-bin/mailman/listinfo/geda-user
