29 Sep
2005
29 Sep
'05
7:30 a.m.
On Wed, 28 Sep 2005, Jeff Walther wrote:
Google for something called a quick-switch, It is basically a single
NMOS transistor transmission gate. Pericom ( and others) make them.
Peter Wallace
Date: Tue, 27
Sep 2005 07:54:24 -0700
From: Eric J Korpela <korpela at ssl.berkeley.edu>
Subject: Re: Tristate Buffer Output if Input is High-Z?
On 9/26/05, Jeff Walther <trag at io.com>
wrote:
Thanks to everyone for all the replies.
It sounds like the tristate buffers don't do exactly what I would like,
although I think I can make it work with more logic in front of the control
line for the buffer.
However, doing a bit more research, it looks like what I really need is a
Transmission Gate. The important difference is that a transmission gate
will pass the input regardless of its state, so L passes L, H passes H and Z
passes as Z. The disadvantage is that if you have a noisy signal, the TG
doesn't clean it up at all the way a TB will.
The catch is that I cannot find one listed anywhere as a part that one can
actually buy. Are transmission gates purchasable parts? Or are they just
something they discussed in my VLSI textbook?
If a tristate buffer is enabled by its control line, but the input to
the buffer is at high-Z is there a typical output?
If there is it probably varies between parts. If you need a defined output
for tristated inputs you should pull the inputs up or down.