On Thu, 30 Dec 2010 00:27:56 +1300, "RussellMc" said:
> Be aware that if you want complete cutoff of a channel using
> transmission gate type technology, then having a hard output clamp can
> be a very good idea.
> Depends on what you think "off" should really mean.
>=20
> This can be a low cost FET to ground, or a back to back pair if output
> is bipolar (with a little magic gate drive), or probably a
> transmission gate would suffice.
>=20
> I had an ultrasonic signal in the tens of volts range driving a loop
> (inductive power transfer) and wanted to signal at mW level over the
> same circuit  with inductive power transfer  off. The clamp FET gave
> me the "rather large" amount of overall attenuation required.

2SK30A JFET is very good for that, I have used lots of them. No need to
do back-to-back. It's very 1980's and I was glad to see there are some
chips that do what I want.

Thanks, Bob

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