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From: Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Newsgroups: sci.electronics.design
Subject: Re: fast discrete PHEMT one-shot
Date: Thu, 16 May 2024 00:00:56 -0000 (UTC)
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Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net> 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