Eaglesp3 Help

Tutorial 4: Defining new spice3 model files


From the eagle control panel, again double click onto the "dc" schematic symbol.

You may have asked how does spice3 knows about modelling the "DIODE". Spice3 knows about the physics of a diode. But the right parameters have to come from outside. In Eaglesp3 the information comes from the name value. Just change it like the resistor value to 1n4148 and press F12. Spice3 will complain that it is

  unable to find definition of model 1n4148 - default assumed.

To fix this, there must be a diode model file called 1n4148.mod residing in your model library directory, eg. /home/yourname/eagleworkdir/spice3lib/1n4148.mod. This is the same for the DIODE model DIODE.mod which came with this distribution and contains only one line (note that the filename must match the model name, besides upper/lowercase):

  .MODEL diode D(IS=1e-13).

If you like, you can define the new model file "1n4148.mod" with your favorite texteditor. It should contain one line:

   .MODEL 1N4148 D(IS=0.1P RS=16 CJO=2P TT=12N BV=100 IBV=0.1P)

Put it in your spice3 library directory and start the simulation again. The error message should have gone away.

Quite another case is the transistor model handling, eg. a NPN transistor. In this case, the environment expects to find a complete subcircuit ".SUBCKT" definition, not only a .MODEL statement. Have a look into the NPN.mod file (you know already where to find it, don't you):

  .SUBCKT NPN C B E     # start subcircuit NPN definition
  .MODEL NPN NPN (IS=1E-14 BF=100)  # define transistor model NPN
  Q1 C B E NPN  # insert the part NPN
  .ENDS        # end subcircuit definition

Further model handling details are described in the elementary device reference pages.

You may download a lot of models from semiconductor manufacturers websites and use it in this environment (may be after a few modifications).

This manual deals only with the model handling of the environment.  To understand more about the spice3 models itself, you will have to consult the spice3 manual, or any textbook about the subject.


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