At high temperatures the circuits with the additional diodes in series
with the base will have problems with transistor leakage currents when
all inputs are low.
The person who created that page doesnt know how to design reliable
circuits.
A base to emitter shunt resistor is one way of avoiding this problem.
Bruce
Stanley Reynolds wrote:
Knowledge of history doesn't = having lived it :-)
http://www.play-hookey.com/digital/electronics/dtl_gates.html
3 to 1 is not all that odd if you have 5 to 1 and 2 to 1 ratios as the page
above indicates.
Stanley
----- Original Message ----
From: Bob Camp<[email protected]>
To: Discussion of precise time and frequency measurement<[email protected]>
Sent: Fri, January 8, 2010 8:10:34 PM
Subject: Re: [time-nuts] Digital Clock kit - no Integrated circuits!
Hi
It seems like the diode to resistor ratio is a bit off in that design.
In order to go into further detail, I would have to admit to starting out in
the pre-integrated circuit logic era ....
Bob
On Jan 8, 2010, at 8:07 PM, Tom Clifton wrote:
http://transistorclock.com/ has a very interesting (though a bit expensive) kit for
sale. A 10" x 11" circuit board sporting nearly 200 transistors and 600 diodes
to drive six seven-segment displays. Suitable for framing... As delivered runs on 60hz
but there is a note about conversion to 50hz mains. You can buy a bare board, just the
components or a full kit.
You must see it to believe it!
Tom
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