This is a Constant Current Source LED Driver, When the LED driver Upper-NPN is driven by a voltage thru 4.7K the LED lights up. Assume that the Lower-NPN at bottom is absent. The current via LED and NPN is limited by R. 20mA may be ok 15mA even better. Or LED blows even transistor goes.
source:http://schematics.blogspot.com/2007/02/constant-current-source-led-drive.html
Thank you.
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This entry was posted on Sunday, May 18th, 2008 at 9:00 am and is filed under LED Flasher, Lighting.
