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Re: Spice models of laser diodes?

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I'm all for pushing the envelope, there's no hide at stake here. :)
It sure looks like it will work. It's 'competing' with systems that can do
100 or 200 KHz at best generally, and none of these devices are needed to go
further. They work alongside laser systems incapable of more that 10 K, often
as not.

The main point is to see what's possible, and to establish the safe operating
area so when I really want to use this thing I can have a very good idea how
to make it right, at more reasonable figures. And I'll know it will draw a
very clean line, which is what the people most likely to use it would want it
to do.

But I still want a good laser diode electrical model.. :)

Re: Spice models of laser diodes?
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You can only try that on a breadboard, not SPICE. And then you find out
that it can do 250kHz but after switching to a different manufacturer's
LM317 ... *POOF*


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I'd rather prefer a nice bottle of Chateau d'Yquem :-)

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: Spice models of laser diodes?

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Sure, but again, that's part of the appeal of making widgets that all use a
single device or small number of parts. Means such adjustments don't have to
be made that often. And again, this is as much as exercise in establishing
safe operating areas, as much as anything else...
 
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Does it talk? (Python joke :)

Re: Spice models of laser diodes?
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For a one-off prototype you could be ok.


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No, but it can make you talk :-)

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: Spice models of laser diodes?

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Or any number of one-offs. That's actually the idea. Where labour is the
biggest obstacle (lack of automation, and a desire to do as much of it here
as possible), it pays to make a few widgets for a small demand, as one-offs,
and test them individually too. And an LM317 is very convenient, a lot of
function hiding behind three pins, and enough heft to do serious work of its
own. It's a very attractive device and saves a LOT of board layout work.


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Careful what you wish for! >:) I have a hair trigger as this thread shows..

Re: Spice models of laser diodes?

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The higher-voltage ones ARE pin diodes. They can make excellent drift
step-recovery diodes and impact avalanche diodes. Need 1000 volts in
100 picoseconds?

John



Re: Spice models of laser diodes?
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Do you have some examples and pics? That would be interesting, I have
use the 1N4007 as a RF PIN diode but never as SRD.

One of my next projects needs the opposite, briefly and automatically
disconnecting an RF amp from a several kV pulse path so it doesn't go up
in smoke. The kind of stuff where people often say "you can't do that".
I love it when a project like this comes along.

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: Spice models of laser diodes?

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Google "Grehkov diode". He's a Russian guy who discovered the DSRD and
impact avalanche effects in cheap power diodes.

Also look for papers and patents by Thomas E. McEwan.

We did one water-cooled DSRD pulser that makes -2KV pulses, about 2 ns
wide, at 500 KHz. We forward-bias a secret diode at +48 volts for
about 80 ns, to let the current build up to 50 amps or so, then
reverse-bias it from a 400 volt supply and wait for it to snap.

Here's the pulser head...

http://www.highlandtechnology.com/DSS/T220DS.html

with the serious parts bolted to a gold-plated copper block. A
water-flow cold plate gets bolted to the bottom.

I can show you innards privately. The HV, high power PIN diode turned
out to be unusual.

John



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Thanks, I will check that out.


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That would be nice. My "Reply to" address is valid as is and lands in my
biz inbox. But only if you feel comfortable doing that.

Was this the project from several years ago that started with the FR804?
Take a look at this puppy, fresh out of the gate:

http://www.nxp.com/acrobat_download/datasheets/BYV29FX-600_1.pdf

In the project coming up I need a lot more volts though (10kV range) and
it has to be small.

--
Regards, Joerg

http://www.analogconsultants.com /

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Re: Spice models of laser diodes?

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Yes. We did wind up with a reel of FR804's that snap nicely, maybe
decent PIN diode material, but we went to a bigger part in the end,
higher voltage and more power dissipation.

It was fun, but we only sold a few.

 
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You should probably use real RF power PIN diodes, like
Skyworks/Microsemi/Aeroflex. They have doping profiles that give
absurdly long recovery times, so it takes very little DC to control a
lot of RF. I used exotica because I needed a huge amount of power
dissipation capability when we were running at 500 KHz.

John



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