rickman wrote:
On 11/3/2014 3:08 AM, Rob wrote:
George Cornelius wrote:
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.

I'm sure this guy (who is coming back on this subject regularly) is
not going to consider that low-power. The inverter was driven into
the area between switching to '1' and to '0' by using a feedback
resistor, and so both output fets are conducting and drawing current
from Vcc to Gnd.

If you I am "the guy", whether or not this is low power enough depends
on the power. My understanding is that when operated in the linear mode
significant current can flow in a CMOS device. So likely this isn't low
enough power, no.

I'm very curious about how they do it in the commercial chips. I have
seen block diagrams and they show an amplifier as the first part of the
chip. Maybe the design really isn't all that low power. Rather than
running at low power all the time, they just limit the duty cycle of the
receiver. "Atomic" clocks don't need to monitor the signal except for a
few minutes each day.

I have several battery-powered "atomic clocks" and all of them enable
the receiver only for a few minutes, either every hour or twice a day
depending on the particular design. The receiver I have connected to
my computer is of course enabled all the time.

Many years ago I worked on a "shop-shelf tag" system that used a low
frequency receiver in a single-chip design, and it also had a power
saving mechanism. The tags (powered by single lithium cell like those
used as a BIOS backup battery) were usually in a sleep mode only driving
the LCD, and once every so many seconds they briefly enabled the receiver.
To run an update, the controller sent a wakeup signal that lasted long
enough to get the attention of all tags, then it sent the updates
addressed to each tag, and finally an end-of-transmission signal that
put everything back into sleep mode. The lithium cell lasted several
years, I think.