>
>Thanks to all who replied on this topic. I always knew that feedback could
>alter gain and input impedance, but I never knew that this was true to the
>extent that it made the actual parameters almost irrelevant. I have seen
>many transistor amplifier schematics (everything from audio to RF small
>signal to RF power) and many do not use feedback (especially the power amps,
>but I guess that the designer just makes sure that the drive would not push
>the amp too far.
>
>Also, can feedback alter output impedance? How much do input and output
>impedance vary among various transistors (in the same basic configuration,
>i.e. CE,CB, or CC)
>
Sean;

I have been following this thread from the beginning, and haven't spoken
until now, because what they have been telling you has been accurate.

I graduated in 1976 with a BSEET degree from Va. Tech. EET (Electrical
Engineering Technology) is Electrical Engineering with more focus on
practical application as opposed to theory. I have a textbook which I (and
everybody else I know who used it) believe is one of the best books ever
written on this subject. It covers the details of designing with most
discrete semiconductors (bipolar transistors, FETs, diodes, etc) from a
practical standpoint. It gives the formulas necessary to do an accurate
design, with explanations of what is going on, but without the detailed
theory that is not really nessary to do the design. It explains things in a
simple, easy to understand way. In the case of the information you
specifically requested, they have a table that shows equations for
calculating voltage and current gain, input and output impedance for all
three transistor amplifier configurations.

Try to find it if you can find a used bookstore that has technical books.
BTW If anyone out there knows of such a place, please let me know. The book
is called Applied Electronics" by J.F Pierce and TJ Paulus. It is no longer
in print ( I tried to get another copy of it) and was published by Bell &
Howell. If you have access to a fax machine, I will fax that table to you.
Please, don't everybody on the Piclist ask me to fax it to you.  The ISDN
number of the book, BTW, is 0-675-09139-x. The Library of Congress catalog
card number is
77-184058

Hope this helps!

TTFN :-)