[sdiy] XOR ringmod

[jhaible at debitel.net]

> If the logic 
> levels are considered "N" and "-N", then the XOR ring mod does work 
> just like an analog one given the same input states of N and -N 
> (using rectangular waveforms).  If need be, CMOS logic can actually 
> work with such states as voltages if powered by a bipolar supply.


Right. And that puzzling effect of a full signal coming thru
with just one input signal is covered here as well:
The "quiet" input isn't really at zero, but at its maximum
negative voltage; so you're multiplying your single input
signal with a DC voltage. Or in frequency domain, you get
f_in + 0Hz and f_in - 0Hz.

The EXOR is like a true RM (analogue multiplier) with a comparator
at each input. 

JH.

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