On 08/07/2010 07:31 PM, Richard (Rick) Karlquist wrote:
ulm...@vaxman.de wrote:
blinked. This problem was eventually solved by driving the LED with a
discrete
transistor instead of a free 74AC14 gate and decoupling this driver
with an
RC-combination.
CMOS logic gates have a totem pole output that is famous for "overlap"
where both transistors on briefly turned on at the same time, resulting
in large current spike from the power supply. It would be interesting
to see if this was the problem, or whether it was the "antenna"
connected to the output.
Also depends on the load. If you have enough capacitive load, current
switch-over occurs when both transistors is driving. But with a load
such as a LED, I would suspect it would be too big current load to be
handled that way.
Separate transistor is much better.
Cheers,
Magnus
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