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Thread: OK to operate at the absolute max rating?
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face picon face BY : email (remove spam text)(Olin Lathrop)



Tomás Ó hÉilidhe wrote:
> Sorry I should have been more specific. Of course I can achieve what I
> describe above by just getting two FET's, one NPN and one PNP,

I'm guessing you keep your NPN and PNP FETs in the same drawer as those jars
of positive electrons and negative resistors?

{Quote hidden}

So forget about trying to drive two-lead bicolor LEDs with apposing diodes
of the two colors.  Common anode or common cathode is easier to drive and
fits nicely with a column and row arrangement multiplexing arrangement.  The
other advantage is the duty cycle can be much higher, thereby requiring
lower on current for the same apparent brightness.  For N total LEDs, the
duty cycle can approach 1/SQRT(N), whereas with a single LED drive at a time
it can't exceed 1/N.

So have you done your homework yet to see how bright a LED looks at 20mA for
1/50 of the time?


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