LTSpice – How to Define a SPICE Model Based on an Existing Model

ltspicespice

I downloaded a BSIM3 model which contains a lot of parameters. Its definition is like this:

.MODEL CMOSN NMOS ...

Now I want to define a model based on this BSIM3 model which just adds W, L parameters.
I add this directive and modify the symbol model name.

.model MOSW CMOSN L=0.25u W=0.375u

enter image description here

When I run, I get the error message:

m2:Can't find definition of model "mosw"

The error log tells me:

Unknown model type "cmosn" -- ignored

It seems that this way not works. So how to define a SPICE model based an existed model?

Best Answer

The manual for NGSpice gives the minimal model for a MOSFET as follows:

.MODEL MOSN NMOS level=number version=number.number.number

The word NMOS is a device keyword, indicating the name of a kind of device that Spice knows about. (It is not the name of a "base" model. Level defines the mathematical model. See manual section 11.2)

You can give parameters in the instance or in another model.

So you take your

.MODEL CMOSN NMOS ...all the params...

and make

.model MOSW NMOS L=0.25u W=0.375u ...all the params...
Related Topic