Modeling of BJT Ic vs Vce characteristics in Pspice

Yes there is, I think a controlled current source is 'G' but that may only be for voltage-controlled current sources.

SPICE transistor models are pretty obscure, but if I remember correctly the Early voltage* gets entered directly into the model, so you shouldn't have to dink with funky sources to model its effect.

• Do a web search if you don't understand what a BJT's Early voltage is.

Hello Viren,

Yes, there is. "F" is the current controlled current source.

Hope this helps,, Joerg

But "F" only allows a fixed "gain" to be set.

If you want a behavioral current source use "G" which has allowed expressions for some time now.

...Jim Thompson

Hello Jim,

Oops, must have misunderstood, I thought a fixed gain is what he wanted.

Anyway, this looks like one of those homework questions. If true, it would be a nasty homework, forcing students to model with current sources. I have seen transistors modeled this way only once and it was quite confusing. The regular model statements make more sense.

Regards, Joerg

Some 20 years ago now my oldest son and I wrote an executable (in Pascal) that would take IC and IB data versus VBE and VCE and find all the model DC parameters.

Nasty set of non-linear iteration.

...Jim Thompson

Hey, that sounds like a very useful program, how about posting it for the gang?

I'll try. It's probably been almost that long that I stopped using it, since the foundries started modeling devices themselves. But I vaguely recall seeing it somewhere... probably on the CD where I backed up all my 5¼" floppies ;-)

I probably also have the mathematical development somewhere on paper. An employee of mine at GenRad (Phoenix), John Spellman, did all the cranking.

...Jim Thompson

Much appreciated.

Just as expected, found it on my 5.25" floppy archive CD done in 2000.

Amazing how small stuff was back in the late '80's, early '90's ;-)

The modeling stuff is at...

This is Pascal, and I don't remember how it works... but it obviously runs in DOS.

Since my oldest son wrote it at age 18-19, while he was at U of A, it is extraordinarily well documented in-line with the code.

I haven't found Spellman's derivations yet. But think about it, if you plot IC and IB (log axis) versus VBE (linear), you will get straight lines until you hit crowding (IKF) or, on the low current end, recombination (NE, and associated terms, from whence the name of the program ;-)

...Jim Thompson

Great!

And wants a Hercules adapter, although perhaps most graphics cards provide that functionality? The program faults, with a "Turbo Graphix error #1", "font file missing in InitGraphic".

Jim, what about the Spanish-language mode in the program?

I didn't try running it... I'm still re-installing taxes on the new machine :-(

Is there really a "Spanish-language mode" there? I can't say that I'm surprised, Aaron speaks fluent Spanish and Portuguese... my Hispanic son-in-law doesn't ;-)

...Jim Thompson