Date: Monday, January 25, 1999 11:07 AM
Subject: RE: [TRLog] Need help with Keying/PTT/Paddle interface
>
>> Good point - the darlington adds one diode drop to
>> the Vce saturation voltage! Exactly how low do the
>> modern transceivers need to go anyway? One would think
>> that pulling them down to 1 volt would do the trick.
I don't think a darlington adds a drop to Vce, it would add one diode drop
to Vbe. In a darlington, two base-emitter junctions are in series but there
is nothing in series with the "main" collector-emitter junction.
If you're pulling voltage down low enough for a TTL logic zero, or if you're
turning off a transistor, you need to go a lot lower than 1 volt. Maybe a
couple of tenths ...
73,
Nick, WA5BDU
--
FAQ on WWW: http://www.contesting.com/trlogfaq.html
Submissions: trlog@contesting.com
Administrative requests: trlog-REQUEST@contesting.com
Problems: owner-trlog@contesting.com
Feature Wishlist: http://web.jzap.com/n6tr/trwish.html
|