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From: Phil Hobbs <pcdhSpamMeSenseless@electrooptical.net>
Newsgroups: sci.electronics.design
Subject: Re: 50 ohm termination
Date: Tue, 18 Mar 2025 22:46:55 -0000 (UTC)
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Toaster <toaster@dne3.net> wrote:
> On Mon, 17 Mar 2025 19:17:13 -0700
> john larkin <jlArbor.com> wrote:
> 
>> On Mon, 17 Mar 2025 19:50:17 -0400, Toaster <toaster@dne3.net> wrote:
>> 
>>> Thank you for the advice. In my case I have a 10Mhz signal with very
>>> sharp transitions (500ps, 5V) and wanted to make sure I did things
>>> properly.
>> 
>> Interesting. What's generating the 5v signal? Lots of AC and Tiny
>> Logic chips are that fast, but might strain to drive 50 ohms. We use
>> several tiny triple buffers in parallel sometimes.
>> 
>> Regular thick-film surface-mount resistors are fine as terminators at
>> 500 ps.
>> 
>> LVDS line receivers are great at the receive end.
>> 
>> 
> 
> I used a THS3111CD. Split up my project into a timing and driver board,
> so i have some 50 ohm BNC cables between and wanted to be extra safe
> about reflections at these higher frequencies.
> 
> 

Hmm. 5V in 500 ps is pretty good going for a part with 1300 V/us slew. ;)

Cheers 

Phil Hobbs 

-- 
Dr Philip C D Hobbs  Principal Consultant  ElectroOptical Innovations LLC /
Hobbs ElectroOptics  Optics, Electro-optics, Photonics, Analog Electronics