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I am using ltspice and I would like to simulate integrated full custom circuits for educational purpose.

I found the NMOS4 and PMOS4 models but there are not enough since there are too ideal there is i.e. no Early Effect.

Are there any possibilities to get a free spice model which includes the basic effects of the FETs and in which I can modify width and length like in the NMOS4 and PMOS4 models?

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If you're just looking for a rough model, then there are two sources of IC models that are free and readily available. The first is ASU's Predictive Technology Models, which allow you to download models that should be representative of a particular process node. These models let you go way down in feature size (e.g. 7nm), but they are predictions of what that process node looks like. The newer models use BSIM4, and I'm not sure if that is supported with LTSpice. The other is the post-run SPICE measured date provided by MOSIS on some processes. This will give you measured parameters for an actual IC run, but it is only available on some of their older(est) processes.

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  • \$\begingroup\$ Ok it looks like this mosfets models are not suitable to modify the width. I want to simulate mainly current mirrors, gain stages and differential amplifiers. So I need to be able to change the geometry on the fly \$\endgroup\$
    – TM90
    Commented Sep 26, 2014 at 14:07
  • \$\begingroup\$ @TM90 You may need to do some research to figure out how to use LTSpice to adjust device parameters, because these are scaleable models. \$\endgroup\$
    – W5VO
    Commented Sep 26, 2014 at 14:14
  • \$\begingroup\$ Ok it works I just had to .include the ptm model. \$\endgroup\$
    – TM90
    Commented Sep 26, 2014 at 17:16

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