From: john/lori (lgnjh_at_earthlink.net)
Date: 2007-04-21 13:39:29
Daniel O'Shea wrote:
> I apologise, I wasn't intending to open up such a can of worms! As I
> stated in my original post, I have a variable voltage of 0 to 5V (no
> microcontroller involved) that I want to translate in to a variable
> current using a transistor. And so, I am lead back to my original
> question - what kind of transistor and what value would work best to
> provide a variable current which duplicates the potentiometer's variable
> current? and do I need any extra components besides just a transistor?
> thanks!
>
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>
After thinking about it a bit, here's what I came up with.
I'm not optimistic about it's behavior, (non linearities and
such).
I didn't go so far as to breadboard it or even simulate it,
it's just some doodling.
No doubt it would have to be tweaked.
I was figuring for 2N3906, 2N3904 but I doubt it's critical
(any roughly similar transistors would probably do).
Note there's an inversion, a higher voltage in would
give a lower reading.
+5V
|
+---------+
| |
3.8K 390 ohms
| |
| +----+
| V |
0-5V | |/pnp |
IN o--13K--+--| |
| |\ |/npn
| +--|
| |\
| V
18K +---o POT
|
_|_
/// gnd
bogax
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