Re: The bi-polar transistor at RF

From: Paul Burridge (pb_at_notthisbit.osiris1.co.uk)
Date: 07/23/04 

Date: Fri, 23 Jul 2004 22:54:12 +0100

On Fri, 23 Jul 2004 11:40:56 -0700, Roy Lewallen <w7el@eznec.com>
wrote:

>Depends on the accuracy you're looking for and the range of operation. A
>simple transistor model, such as one made from data *** parameters,
>will work surprisingly well for many purposes. But it's a linear model,
>good only for a very limited range of operating conditions. In a real
>transistor, Ccb (for example) varies strongly with Vcb. A complete SPICE
>model accounts for this, along with several tens of other factors
>ignored by simpler models. If you're operating the transistor with a
>small signal and at voltages, currents, and frequency near those on the
>data ***, a simple data *** model can often be good enough.
>
>One of my most treasured texts is _Modeling The Bipolar Transistor_, by
>Ian Getreu, published by Tektronix in 1976 (Tek P/N 062-2841-00). It's
>long out of print, but it might show up on eBay or elsewhere from time
>to time and I highly recommend it to anyone seriously interested in
>transistor modeling.

Thanks, Roy. It's a pity Kevin (for whom I apologise) lacks the depth
of knowledge that so many advanced "build-it-yourself" radio amateurs
have acquired over many years of hands-on experimentation.
I'll certainly try to get hold of a copy of this book. It sounds just
the ticket for my purposes.
Your reply throws up another interesting question: which model
parameters are essential for adequate modeling of the BJT up into UHF,
and which, by their omission, call the model's reliability at beyond
such high frequencies into question?
Thanks,

p. 

-- 
"What is now proved was once only imagin'd." - William Blake, 1793.