bjt and mosfet current dependence

s depend on collector and drain currents and voltages? How much will the ef= fective resistance of these devices change depending on the current that fl= ows through them?

effective resistance of the device. I'm needing to know how the resistance= will change given different operating conditions.

resistance

y alone. That is, I'm looking for a formula R(Ib,Vce) for an ideal bjt and = mosfet. It would also be very useful to have the formula depend on non-idea= l characteristics of these devices to increase the accuracy.

Search on Ebers-Moll and Gummel-Poon.

This should really have been posted to sci.electronics.basics

Here we bitch about the deficiencies in the Gummel-Poon model as embodied i= n the (free) LTSpice circuit simulation program, which comes with built-in = models for most widely used transistors and FETs, and advice on how to get = the manufacturers' Spice models for other parts and plug them into LTSpice.

--=20 Bill Sloman, Nijmegen

Funny, though you seem perhaps to have some knowledge, I have not seen you in any spice discussions of late.

It's a while since I complained here - on January 14 - about not being able to get LTSpice to simulate squegging in Peter Baxandall's Class D oscillator with a big feed inductor. The thread ended up with 32 posts, none of them all that helpful.

Presumably I could do it with a VBIC - Vertical Bipolar Inter Company - model of a bipolar transistor, which LTSpice does support, but the VBIC parameters seem to be known only to manufacturers and people with the gear to measure then directly.