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NNTP-Posting-Date: Wed, 19 Mar 2025 14:41:15 +0000
From: john larkin <jlArbor.com>
Newsgroups: sci.electronics.design
Subject: Re: 50 ohm termination
Date: Wed, 19 Mar 2025 07:41:10 -0700
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On Wed, 19 Mar 2025 06:23:25 -0400, Toaster <toaster@dne3.net> wrote:

>On Tue, 18 Mar 2025 19:01:51 -0700
>john larkin <jlArbor.com> wrote:
>
>> On Tue, 18 Mar 2025 18:59:44 -0400, Toaster <toaster@dne3.net> wrote:
>> 
>> >On Tue, 18 Mar 2025 16:02:45 -0700
>> >john larkin <jl@glen--canyon.com> wrote:
>> >
>> >> On Tue, 18 Mar 2025 18:29:42 -0400, 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.
>> >> 
>> >> Is the signal some analog thing, or a 10 MHz clock? The THS is an
>> >> opamp, but they can make good cable drivers too, even for clocks.
>> >> 
>> >> Lately I'm enamored of BUF602, a unity-gain 1 GHz beast.
>> >> 
>> >
>> >I had a really hard time finding a good line driver. I might look
>> >into this chip.
>> >
>> >Thank you!
>> 
>> Is your signal analog or digital?
>> 
>
>digital

I use Tiny Logic triple buffers as line drivers, with all three
sections in parallel, and then sometimes two or three chips.

NL37WZ16US costs 10 cents.

https://www.dropbox.com/scl/fi/gw7wetgtovqc04as2gxol/NL37WZ16_5V_Pulse.JPG?rlkey=2eqbyhds8l1myrzfjsrqwn5b3&raw=1

That US8 package is nasty to solder or probe.