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From: Winfield Hill
Subject: Re: Solar Cell Voltage Booster?
Date: 17 Dec 2002 04:34:26 -0800
Organization: Rowland Institute
X-Newsreader: Direct Read News 4.20
> Well Now. Exuse me ... I'll answer my own question here.
> Well Tony you could try a simple push pull transformer based
> inverter design. Obviously silicon transistors are out of
> the question so you would have to use germanium with there
> lower 0.2 - 0.3 VBE voltage. ...
Silicon transistors and MOSFETs have no problem switching low
voltages, capable of stepping up even 10 to 20mV if need be.
The issue with low supply voltages is operating the control
circuit and driving the transistor bases or the FET gates.
A common approach allowing you to use conventional circuitry
is to operate the power stepup circuit from its output. Now
the problem, of course, is how to get it started. A small
starting battery is a simple solution. If that's distastful,
this is a still a much simplified problem, because it's a
low-current requirement, and poor efficiency is OK.
A two-stage starting circuit can also be used. Let me give
you a few interesting data points to whet your appetite: the
required Vbe voltage for a 2n4401 npn transistor operating
at 0.1uA is about 350mV, and for a 2n4403 pnp about 400mV,
well under your cell's 0.5V. You see my drift here?
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