Boost Dieing AA

Google-search for "joule thief".

-- Dave Platt AE6EO Friends of Jade Warrior home page:

That is not what I am looking for. Germanium transistor not silicon.

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Works the same either way.

Perhaps you're thinking specifically of an old Fred Nachbaur circuit which appeared in Electronics Now, I think ca. 1995? IIRC, it was a two-transistor chopper, which is just a two-headed joule thief.

LOL, we've been here before..

Can't find any hits online.

Tim

-- Deep Friar: a very philosophical monk. Website:

What's the point? There's no energy left in the chemistries I can think of at 0.3v.

I've made simple boost converters from silicon BJTs that work to ~550mV. Theoretically you could get lower than that--Si BJTs still work well below 600mV Vbe if i(c)'s super low enough. But, there's no point. The i^2r losses make it grossly inefficient, and the battery realities are that there's nothing there to harvest.

Win Hill's reports almost tempted me into making a, say, 10nA bootstrap stage, just for silliness. But, I got over it.

Search back in the archive for Jan's thread on BF862 millivolt oscillators.

Cheers

Phil Hobbs

Also:

- A Joule Thief circuit can be built with a germanium transistor, just as easily as with a silicon transistor. I expect it would work down to somewhat lower supply voltages.

- The Wikipedia article on "joule thief" (the first result returned by a simple Google search) cites a competing circuit which uses a depletion-mode JFET in place of a bipolar transistor. It was originally patented for use with extremely low-voltage sources, such as a thermoelectric generator or "PowerPile". The circuit can be seen at

and as the patent was filed in 1987 and issued in 1988 I believe it would have lapsed no later than 2007. Should be fair game to use this circuit in the U.S.