I recently bought a gas water heater and made a point of getting one that didn't require external electrical power to operate.
To my astonishment, it nonetheless came with what behaves like a digital controller, complete with a green LED status light that must require close to 3 volts to turn on.
The electronics are operated from a standard Honeywell thermopile generator producing 750 mV open circuit with a 3 ohm source impedance. I expected to find an explanation of how it's done via a quick Web search, but have so far come up with nothing very informative: Only that one can get MOSFET transistors "programmed", evidently by something like charge trapping, to have arbitrary gate threshold voltage, down to zero. That seems rather exotic for a water heater 8-)
Can somebody point me to an application note explaining how this is done?
Thanks for reading,
bob prohaska