TTL homebrew CPUs
cclist at sydex.com
Tue Jul 10 01:28:25 CDT 2007
On 9 Jul 2007 at 23:23, woodelf wrote:
> But with a ka-zillion tunnel diodes you can build the fastest
> computer ever. Well that was what all the hype was about in the
> early 60's.
> Did anyone ever use Junction Fets in computer logic?
I doubt it--the transition seemed to be from bipolar to MOS in
integrated circuits. JFETs in digital logic seem to have been
I've still got my GE tunnel diode (and SCR and Rectifier) manual.
Lots of interesting circuits, but nothing that could have been
constructed using other semiconductors at the time. There are some
logic circuits in the book, however.
Negistors, it turns out, are pretty easy to build. There's a web
site that describes how to make simple ones using a sheet of
galvanized steel. "Accidental" negistors by way of point-junction
devices have probably been reported since the 1920s or earlier.
Another 2-terminal semiconductor that I like is the diac. Can be
used for relaxation oscillators, but up until a few years ago, I had
one hooked in series with the line going to my answering machine.
The moment the line is picked up at a phone anywhere within the
house, the answering machine is electrically disconnected and doesn't
interfere with the call. Also useful for building simple relaxation
oscillators--and, of course, triggering triacs.
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