From: Mike Monett
X-Mailer: Mozilla 2.02 (Win16; I)
Subject: Re: Prof Searle's 100MHz 30dB 1968-era 3-trannie amplifier
References: <3E2358BE.email@example.com> <3E2A0C89.7FAB@sneakemail.com> <3E2A4E8D.78BE@sneakemail.com>
Date: Tue, 21 Jan 2003 07:47:55 -0500
NNTP-Posting-Date: Tue, 21 Jan 2003 07:47:22 EST
Organization: Bell Sympatico
Winfield Hill wrote:
> Mike Monett wrote...
> > Now I'd like to see how it really should be done!
> Nah, your circuit the looks like the winner. But I'll show you my
> 2n918 circuit if you show me yours. :>)
> - Win
OK, I put mine up. Can we take a peek at yours? I'd like to see what
supply voltage you used, and how you got rid of the bypass.
This circuit is deceptively simple. But due to the voltage stackup, you
gotta have a plan, or you end up with problems like mine has. What's your
plan, and how did you distribute the voltage between the two gain stages?
The other gotcha is you are restricted to a fairly narrow range of
collector resistance to maintain bandwidth. But this leads to dissipation
problems in the transistors.
Another problem is to meet design goals with 1960's era transistors. The
30dB gain figure was only a recollection. The statement "flat to 100MHz"
dos not tell us where the -3dB point was. Perhaps with modern tools, we
can get a fairly good idea of what it might be.
So the circuit is not as simple as it looks. I showed the wrong way to do
it. What's the right way?