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Sensor circuit

I was just looking over the circuits that have been stolen from the
design manual.  Our sensor circuit uses the full wave rectifier from
page 146, fig. 6.73, right?  The two diodes in that circuit will remove
any signal from between -0.7 and +0.7 volts.  At first I thought this
was a bad thing and was going to suggest a simple super-diode.  However,
the actual effect of the diodes will be to limit noise from our circuit.
What this means in practice is that you can stick an even larger resistor
onto the peak rectifier and it should still never end-up amplifying
noise!  I think we should try using some bigger (perhaps much bigger)
resistors in the rectifier.

[I seem to remember the peak rectifier getting digital input, but I
 can't remember you adding a digitizer anywhere in the circuit...
 Arg.  This must be my imagination?]

I also thought of yet another way to make the short-range sensor's
range still shorter by inverting its input signal, but after some
consideration, I think just connecting after only three stages (or after
four stages since even just bypassing the full wave rectifier may decrease
its range significantly) is still better.  As you noted, we may not
even want to decrease its range --- just so long as the circuit is
constructed that this is an option.

I'd like to have a chat with you over the weekend sometime.

Signature withheld by request of author.