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.

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.

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.


             Russell
--=20
http://www.piclist.com PIC/SX FAQ & list archive
View/change your membership options at
http://mailman.mit.edu/mailman/listinfo/piclist
.