Re: Driving tri-state LED matrix

Tomás Ó hÉilidhe wrote:
"MK" <nos...@xxxxxxxxxx> wrote:

In your circuit a big current will flow from VCC through the
emitter and out of the base of the first (leftmost) PNP
transistor, into the base and out of the emitter of the NPN
transistor. The second PNP transistor will turn on, the first
two transistors will be destroyed.

See this is exactly what I was thinking... but miraculously this
worked perfectly in my college project. Even if my board mixed up
the collector with the emitter for one of the transistors, it still
doesn't explain why both transistors weren't always turned on... ?!

Transistors work with emitter/collector exchanged. Their
efficiency, Vcc, etc. are sharply curtailed. They are not
characterized for such operation.

--
[mail]: Chuck F (cbfalconer at maineline dot net)
[page]: <http://cbfalconer.home.att.net>
Try the download section.

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