Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Bill Sloman Newsgroups: sci.electronics.design Subject: Re: fast discrete PHEMT one-shot Date: Sat, 18 May 2024 15:58:09 +1000 Organization: A noiseless patient Spider Lines: 92 Message-ID: References: <48na4j10neo6bru36kllgm3447dclcrfgg@4ax.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Date: Sat, 18 May 2024 07:58:24 +0200 (CEST) Injection-Info: dont-email.me; posting-host="8c9b35e36545cc12300428201b91ce18"; logging-data="2799031"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18GB82zHw2lLXaUi4EH6R6Ij57tGSeAIRc=" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:cxM6qM/IIETDf/7COTM8dqoEK+I= Content-Language: en-US In-Reply-To: Bytes: 4815 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 >> wrote: >> >>> John Larkin 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