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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: another fast one-shot
Date: Thu, 13 Jun 2024 16:03:04 +1000
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On 13/06/2024 4:11 am, john larkin wrote:
> On Wed, 12 Jun 2024 17:22:49 -0000 (UTC), Cursitor Doom
> <cd999666@notformail.com> wrote:
> 
>> On Wed, 12 Jun 2024 09:33:17 -0700, john larkin wrote:
>>
>>> Here's another idea for a fast one-shot. This is the just-apply-money
>>> version and should get close to 1 ns pulse width and should easily
>>> trigger at 150 MHz.
>>>
>>> https://www.dropbox.com/scl/fi/1okfo8964bw5m53mjmxs6/
>> Pecl_One_Shot_1.jpg?rlkey=dwus6qjyqsynl2rv6uje2xxtj&raw=1
>>>
>>> I can use the other half of the dual comparator elsewhere. This one has
>>> programmable hysteresis too.
>>
>> Exposing my contemptworthy ignorance here no doubt, but what exactly is it
>> that is fast about this design, John? And what would its application be?
> 
> It would have a leading-edge prop delay of 350 ps, a minimum pulse
> width just over 1 ns, and would easily trigger at 150 MHz. Integrated
> one-shots, xxx123 types, are always terrible, even the obsolete ECL
> ones.
> 
> It would be a programmable delay in a number of possible products,
> including some optical modulators. Just playing right now.
> 
> More dollars could certainly do something faster, but as long as
> customers connect boxes with cables, faster isn't worth a lot. Light
> just moves too slow.
> 
> Any suggestions for a faster one-shot?

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It's just a two transistor emitter-coupled monostable, but with the two 
transistors as BFR92's run at 10mA,  it produces 1nsec pulse without fuss.

Finding the broad-band PNPs to let you translate the output pulse to a 
useful voltage level is tricky. Phil Hobbs has told us that there is a 
least one still in production and available.

-- 
Bill Sloman, Sydney

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