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Author Topic: Low Threshold Diode  (Read 8803 times)

Offline joegatt

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Low Threshold Diode
« on: February 23, 2007, 10:34:14 PM »
Picture this... you have devised a way to build yourself an array of tiny wind turbines using small off-the-shelf motors. If the output from the motors is pulsed DC, it can be smoothed and combined together. If the output is a.c. at a mere 2V or less, there is a problem.

The outputs cannot be easily synchronised, unless the rotors can be mechanically linked together. The obvious solution is to rectify the output from each alternator, but most diodes have a forward threshold of 0.7V. With Germanium this drops to 0.3V but may still be too high.

A workaround one can try, is to use a transformer to step-up the voltage before rectifying.  The impedance would need to be carefully matched, but this setup will always introduce some inefficiency.

A depletion MOSFET can be wired up as a diode with virtually no forward threshold simply by shorting the gate to the source. I tried this successfully using a BUZ31 and tested it on my homebuilt alternator.

However with lower voltages or shorter pulses, one might need to use a MESFET as suggested in US patent number 6097247. I was wondering if anyone here had experiences with this, or other ideas for combining the outputs.