Al, thanks so much, that's immensely helpful! 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 >t o 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
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