Quote:
Originally Posted by Synchrodyne
I notice the H&H example current-driven demodulator had two diodes in a voltage-doubling mode.
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No they are not.
The deceptive part of the H&H circuit, I've mentioned this on another thread, is that it looks exactly like a voltage doubler but it isn't and it doesn't double voltage.
Notice the the very low value of resistor that these diodes ultimately load into. It is actually, for practical purposes, a "shorted out voltage doubler" the output resistor 100R load is doing the "shorting" and is actually acting as a current sense resistor on the output.
This is why it is not like any other type of rectifier-detector circuit you will see, because its operating principle is entirely different.
The diodes are current driven (not voltage driven) into a low R load. This is why not only is the linearity excellent but it goes to an extremely low input voltage levels. As I mentioned before, its the perfect solution to the problem of an RF volt meter, but it appears ill understood or overlooked.