[sdiy] Sample and holds

[Magnus Danielson]

From: "Paul Maddox" <Paul.Maddox at wavesynth.com>
Subject: [sdiy] Sample and holds
Date: Wed, 6 Jun 2001 21:15:10 +0100

> Dear all,
> 
> Im after a quick sample and hold,
> I need to aquire and sample in about 340nS (yes I did type NANOSECONDS)
> and hold for about 25 uS before drooping any..
> Im guessing a normal FET (4066,4067,4051) type of S&H probably wont be quick
> enough..
> any suggestions?

Well... looking in my 1982 RCA CMOS catalogue suggests the 4066 to be
in that neighborhood allright. Ratings hints towards "on" times downto
20-30 ns so keeping it "on" for 340 ns should as such not be a
problem, rather a fairly good thing. It is however a "dirty" solution
and you could do better. If you want good stuff check out Analog
Devices, Burr-Brown and Harris amongst others. I think Maxim and
Linear Technology is also into similar fields. Hmm... check out
National too...

For me 340 ns sounds rather long, but if you are going to do it DIY on
a shoe-string budget, that is another thing. For some of the stuff I
do 10 ns is a minor lifetime.

> I also need a one of 4 mux that will react well within this time (50nS
> 'ish), I guess Im going to be pushing a 4051
> to run this fast, though this isnt as major an issue as the S&H...

Read your datasheets carefully, these components might do your work
well. However, regardless of what you use, be carefully with
decoupling and routing. You should preferably be running at least
4-layer stuff.

What are you doing anyway?

Cheers,
Magnus