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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: fast discrete PHEMT one-shot
Date: Sat, 18 May 2024 15:58:09 +1000
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On 17/05/2024 12:40 am, Bill Sloman wrote:
> On 16/05/2024 11:15 am, John Larkin wrote:
>> On Wed, 15 May 2024 22:46:27 -0000 (UTC), piglet
>> <erichpwagner@hotmail.com> wrote:
>>
>>> John Larkin <jjSNIPlarkin@highNONOlandtechnology.com> wrote:
>>>>
>>>> https://www.dropbox.com/scl/fi/agatzclr8pvr5470g6mc4/Phemt_One_Shot_1.jpg?rlkey=cwnx0qd7ajgnh8otf627x5lku&raw=1
>>>>
>>>> Regular monostables are terribly slow. This one has low prop delay and
>>>> high rep-rate, if the sim is to be believed.
>>>>
>>>> SAV541 is mostly specified as an RF part, but it's a dynamite switch.
>>>>
>>>> I can post a link to the files if anybody wants to play with this. All
>>>> my values are first guesses, no math involved, and it works!
>>>>
>>>> My SAV541 Spice model is a revision of Phil Hobbs' original.
>>>> Mini-Circuits is adamant that they will never provide Spice models, a
>>>> typical RF-bigot attitude.
>>>>
>>>>
>>>
>>> Yay! Eccles-Jordan ride again.
>>
>> 1918!
>>
>> I think that was a bistable. I don't know when the monostable was > 
>> invented.
> 
> https://en.wikipedia.org/wiki/Multivibrator
> 
> has a two quotes from 1942 one from 1943 and two from 1949 which make it 
> clear that monostable had been invented by then. It sees it as a cut 
> down bistable, so Eccles-Jordan is probably a good name.
> 
> Since the first multivibrator circuit, the astable multivibrator 
> oscillator, was invented by Henri Abraham and Eugene Bloch during World 
> War I, it probably isn't the right name.
> 
> https://apps.dtic.mil/sti/tr/pdf/AD0410225.pdf
> 
> is a 1963 Ph.D. on the bistable circuit.
> 
>> People tend to roll eyes when I use one-shots in logic designs. I
>> can't see why.
> 
> You can't trigger a one-shot immediately after it has been triggered, 
> and the pulse width you get can be reduced if you re-trigger it too soon 
> after it has generated it's pulse, when it hasn't entirely recovered.
> 
> Using a properly terminated delay line to set the output pulse width 
> could reduce this uncertainty, but I've never done it.

Or rather when I did do it

Sloman, A.W. and Swords, M.D. "A fast and economical gated 
discriminator", Journal of Physics E: Scientific Instruments, 11, 
521-524 (1978).

I didn't do it to get a more stable delay but rather because I needed 
narrower pulses than I could get out of any monostable I could buy at 
the time. As the paper notes, the MC10198 could have delivered, but it 
wasn't available when I was putting the circuit together.

One of the delay lines I used - 350 mm of 50R coaxial cable, or 1.6nsec 
- would have been too short for even the MC10198 - but the rest (5nsec, 
10nsec, 20nsec and 100nsec were lumped constant thick film hybrids) 
could have been replaced.
> Ghiggino, K.P., Phillips, D., and Sloman, A.W. "Nanosecond pulse 
> stretcher",Journal of Physics E: Scientific Instruments, 12, 686-687 
> (1979).
> 
> just used two 5GHz wide-band transistors (BFT95) and was perfectly 
> horrible, but it did what Dave Phillips and Ken Ghiggino had wanted me 
> to give them, and Ken Ghiggino wrote it up rather badly, but I was able 
> to rework the short paper into a form that was publishable and looks 
> nice on Ken's CV.
> 
> The fact the laser pulses it was designed to detect arrived at a steady 
> 20MHz meant that it's worst defect didn't matter.

The 5GHz BFT95 was pretty new when I used it, and I got told about it by 
one of the microwave guys at EMI. The Sloman and Swords paper preceded 
the time I could get that kind of advice.

The 2n918 I did use in the 1978 paper was only good for 600MHz.

-- 
Bill Sloman, Sydney