I'm using a model of the CD4007 that a friend sent me. here it is: .model CD4007 NMOS( Level=1 Gamma= 0 Xj=0 Tox=1200n Phi=.6 Rs=0 Kp=111u Vto=2.0 Lambda=0.01 Rd=0 Cbd=2.0p Cbs=2.0p Pb=.8 Cgso=0.1p Cgdo=0.1p Is=16.64p N=1) LT Spice says it doesn't recognize Xj. So I looked it up. It is metallurgical junction depth. I'm not sure why LTSpice doesn't recognize the parameter, maybe my friend copied the model from PSpice, which uses different names for the parameters or something. Anyway, I haven't had much luck trying to find out what LTSpice calls the mystery parameter. Anybody have words of wisdom, or maybe a better .model file for that mosfet? I am looking for the n-mosfet in that chip. And by the way, I asked my buddy why the model says Kp instead of Kn and he said LTSpice can calculate Kn from Kp. Bottom line, I'm not sure this is such a great model to be using.