On 10/29/2014 3:06 PM, Lostgallifreyan wrote:
rickman wrote in :

Actually even single ended digital inputs don't have much hysteresis
unless they are designed for that.

Well, as a proportion if they only go high above soem fairly close approach
to V+, then low when close to 0V, then the dead band could be wide, the aim
was to eliminate false states so they ARE usually designed for it. I take
your point on very low volt systems, if the actual difference is small even
though proportionally it may not be.

Anyway, now I know that the supply is so small, your suggestion of discrete
transistors is almost certainly the way to go, unless there is enough similar
demand out there to have cause an off-shelf part to be made.

Normally I'd just look at how others are solving similar problems, so I guess
the question I can ask is: what is the signficant difference in this case
that prevents the nearest off-shelf answer from working?

What off the shelf answer? I have not seen any all digital receivers
for any frequency. I think it may only be practical for this case and
I"m not sure of that. lol

This signal is very unique in that it has a very low data rate. This
allows integration in the digital domain over a large number of samples.
Theoretically the signal would be detectable with a negative SNR.
There are actually a number of issues I need to solve to get a prototype
working. The big one is being able to get a large enough signal that
even statistically it is noticeable at the receiver input.

--

Rick