[Author Prev][Author Next][Thread Prev][Thread Next][Author Index][Thread Index]

Re: gEDA-user: new to gEDA, diode trouble

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


_______________________________________________
geda-user mailing list
geda-user@xxxxxxxxxxxxxx
http://www.seul.org/cgi-bin/mailman/listinfo/geda-user