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Subject: Re: Constant current source with low voltage drop
Date: Sun, 29 Sep 2002 00:13:35 +0100
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> markp wrote:
> > Hi All,
> > I need a constant current circuit adjustable from 0 to 150mA powered
> > 5V supply. This is to drive LEDs of an LCD backlight. The spec says a
> > 4.4V drop @ 150mA (2 LEDs in series?) so I've got to do this with a
> > of 0.6V voltage drop. Any suggestions?
> > Thanks!
> > Mark.
"Uwe Zimmermann" wrote in message
> what about a resistor and a potentiometer in series. 150mA max at .6V
> drop means 4ohms minimum resistance. Put that in series to a 0..500ohm
> potentiometer and you will get approximately 1mA..150mA range. The
> voltage drop of a diode is almost independend of the current within a
> certain range of operating conditions.
The max drop is quoted at 4.4V, but the min drop isn't, so this might
produce too much current I think.
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