At 11:02 AM 8/18/97 +0200, you wrote:
>> Thanks for the reply, Bob.
>> I guess you are saying that it is up to the actual user of the components to
>> measure their characteristics. For me, there is only one problem with this,
>> I am at this point only an electronics hobbist. I am studying to become an
>> electrical engineer. I don't have the money to buy the test equipment needed
>
>NO. By using apropiate design you can make the circuit
>quite independant of transistor characteristics.
>
>The only really important things is dissipation, minimum
>gain and frequency (The last being almost neglible in audio
>these days). Feedback can take care of *almost* everything else.
>

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)

By the way, to Bob who asked if I was using spice, I am not. I have been an
electronics hobbyist ever since I was about 6! (Of course, not really
seriously until I was about 10). I have tried for a long time to learn about
transistor and IC analog design. I have made a lot of progress, but the fact
that the textbooks I have been using talk a great deal about H params. and I
cannot find them on most datasheets has been I stumbling block to me until I
thought to ask it on the PICLIST.

Thanks again,
Sean
KA3YXM