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From: Winfield Hill
Subject: Re: Explosions in electronics.
Date: 2 Oct 2002 06:19:09 -0700
Organization: Rowland Institute
X-Newsreader: Direct Read News 2.98
Chuck Simmons wrote...
> Saw that. Very interesting. I once built a device that pulsed small
> LEDs to about 3 amps but the pulse duration was maybe 0.5 nsec and
> the repetition rate so low that the LED seemed hardly to light. The
> goal was a fast rise time light pulse and the switch was a transistor
> operated in avalanche mode. The LEDs tended to be more reliable than
> the transistors in this kind of circuit.
> That brings up a question. Does anyone use transistors in avalanche
> mode today?
To me that brings up a different question, how did you get the LEDs
to illuminate and extinguish so fast? I have tried a variety of
visible-light LEDs with 1 to 2ns-long high-current pulses, and found
that I couldn't get the light to respond as fast as the current, in
fact having a time constant of more like 10ns. My short ns current
pulses simply resulted in weak longish 10ns light-output pulses.
To get 10ns instead of 20ns, I had to reverse the current direction
after the first few ns. I tried currents of 0.25 to 10A.
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