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pltmk
05-27-2006, 03:23 AM
Hi·in the " whats a micro controller" book it shows how to control· current with a digitaL pot and an·npn· how could i do the same thing with a pnp? could i use the same digital pot?

Chris Savage
05-27-2006, 04:26 AM
In theory you could...Just remember the PNP will work the opposite of the NPN in that it will be a LOW going voltage that will turn on the PNP.· LOW in relation to its·emitter voltage.· If the base is at the same voltage as the emitter the transistor is OFF.· As the emitter voltage decreases in relation the transistor turns on.· Although transistors are current driven as switches it makes more sense to think of thehigh or low voltage turning it on.· But before I confuse you try reading this link.

http://www.kpsec.freeuk.com/trancirc.htm

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Chris Savage
Parallax Tech Support
csavage@parallax.com (mailto:csavage@parallax.com)


Post Edited (Chris Savage (Parallax)) : 5/26/2006 10:05:28 PM GMT