just found this
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martin
Current sources 101
Apr 01, 2007
6 Replies
Have you found part 2?
Hi John, think that comes out next month
martin
I must admit I use the simple R and LED, and hadn't thought about it that much. But I've never seen the emiitter to ground R before (I'm assuming a pnp).
and, yes, maybe a part 2....
martin
For the simple LED or 2-diode type sources, a major error is the voltage divider formed by the bias resistor and the dynamic impedance of the led or diodes. A resistor from the transistor emitter to ground can cancel this error. Or drive the led/diodes with a very simple, ground-referenced current source. Or bypass the hell out of them.
He doesn't show using an opamp to close the loop around a transistor or fet, which gives better dynamic and temperature performance; maybe in part 2?
John
are you
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?
martin
Well, I just invented it!
John
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