[time-nuts] Homebrew Rubidium oscillator, jitter and other tales :-)

Magnus Danielson magnus at rubidium.dyndns.org
Sat Aug 7 17:48:26 UTC 2010

On 08/07/2010 07:31 PM, Richard (Rick) Karlquist wrote:
> ulmann at 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.


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