Path: ...!weretis.net!feeder8.news.weretis.net!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Phil Hobbs Newsgroups: sci.electronics.design Subject: Re: fast discrete PHEMT one-shot Date: Thu, 16 May 2024 00:00:56 -0000 (UTC) Organization: A noiseless patient Spider Lines: 37 Message-ID: References: <88dc3fcf-7731-cc95-3bb5-80d5cbd6edc9@electrooptical.net> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Injection-Date: Thu, 16 May 2024 02:00:56 +0200 (CEST) Injection-Info: dont-email.me; posting-host="2ac6ef4b2cfc04580f0335287eb003a2"; logging-data="1234935"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX181pgh46HUQqR1HAhiYXtd1" User-Agent: NewsTap/5.5 (iPhone/iPod Touch) Cancel-Lock: sha1:x+kIY+91vwXMi09BqVEcTdipJLw= sha1:ewTfMILuIJC5qtU02m0OsaS7gP0= Bytes: 2396 Phil Hobbs wrote: > On 2024-05-15 12:47, 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. >> > > With a low-resistance drain load like that, you don't care too much > about the low drain impedance of the pHEMT. The old Avago ones were > around 160 ohms iirc. The transconductance is high enough (400 millimho or > something ridiculous like that) that you get gobs of voltage gain even so. > > Really really crappy for followers though! > > Cheers > > Phil Hobbs > -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics