[AMRadio] infinite impedance detector vs diode


Jim Tonne tonne at comcast.net
Thu Sep 4 20:17:44 EDT 2008


John:

I am under the impression that the high input impedance 
of that AM demodulator is perhaps its most important
point.  The fact that it seems to buffer the output load
from the detection action seems nice to me.

I think it could be made temperature-stable rather
easily by adding a diode in series with that 6200 ohm
resistor from the base to ground.  Then change the
resistor.  Base idles about .67 volts above ground so as
to just barely turn on the transistor.

Oh yes - the URL for those that may have missed it:
http://tonnesoftware.com/appnotes/demodulator/diodedemod.html

Yes, it would be possible to do the same kind of look-see
on a product detector.  All it takes is time!  I have some 
other stuff that needs attention right now;  wheels are
squeaking.

- Jim Tonne   WB6BLD   TonneSoftware.com




 


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