Re: another fast one-shot

On Fri, 14 Jun 2024 19:02:11 +0100, piglet <erichpwagner@hotmail.com>
wrote:

On 13/06/2024 07:03, Bill Sloman wrote:

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.
 

>
It is a pity it relies on an input pulse shorter than the output - at
those speeds it would nicer to have a step input somehow?
>
piglet

It's really a slow diffamp, not a one-shot. It will make a nice clean
1 second output, given a 1 second trigger input.