Reece - 2012-06-07

Hi folk. New QUCS user here.

I'd like to model some component-level logic circuits. These are made up of two types of N-channel MOSFETs with a handful of resistors and capacitors tossed in. I'm having trouble creating working models of the two MOSFETs: the BSS83 from NXP, and the FDV301N from Fairchild. I found a Level 3 SPICE model for the BSS83 that doesn't seem to work with QUCS, and nothing at all for the FDV301N.

Just to forestall flames saying "do your own homework", I'm not a college student. I'm a software engineer by profession, and an electronics hobbyist. I'm happy to do research (that's part of the fun), but I need some guidance.

I have both datasheets and actual components. I found some equations that model MOSFETs, and by adjusting some of the parameters missing from the datasheets I can get Gnuplot to generate curves that look a lot like those in the datasheets. But when I try the same parameters in QUCS I get nasty discontinuities around the transition from linear to saturation formulas.

Would some kind soul like to help me out?