On 10/30/2014 01:27 PM, rickman wrote:
On 10/30/2014 1:02 PM, Lostgallifreyan wrote:
rickman wrote in :

Before integration comes demodulation. How would you demodulate and
integrate in the analog domain on a 100 uW power budget? The signal is
PSK. But that is not the real reason. My goal is to show it is
possible to do this entirely in the digital domain.


Low Vf diode in feedback loop of op-amp? I'm curious though, it's an
interesting thought, doing it all in digital equipment, but why? The main
drive behind me 'off-shelf' remark is that I suspect the best answer already
exists in many forms. I'm curious about what makes a need to keep searching.
I'm not denying it, far from it, there's usually more than one good way to
do something, I'm just not sure what the differentiating factor is in this
case.

I don't know about "best" but you can buy a time code receiver chip that
spits out a demodulated signal to be decoded by an MCU. At that point
the data rate is pretty low so an MCU can run at very low power levels,
likely dominated by the quiescent current.

When you suggest an op amp, we already covered that ground and they aren't
low power enough. I'm curious how they amplify the signal in the receiver
chip with the whole circuit drawing a very low power level.

Motorola's app notes on the old 4000 series CMOS included
various analog circuits, including use of a CMOS inverter
as an amplifier. I'm enough of a packrat that I keep those
things.

4000 series may not be useful in your case, but the circuits
or variants of them may apply in newer CMOS implementations.

'Course calling it all digital may be just a game if your
input stage is a digital circuit biased to operate in an
analog mode.

George