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Date: 11/29/02 at 12:06 AM
Posted by: Edd
E-mail: eddw@attbi.com

In Reply to: Hello, I want a precisive current source. posted by Truong An Nguyen on 11/27/02 at 8:04 PM:

Chao Om:
If I read that right you want a regulated constant Current source...right ? Or are you
just wanting an adj power supply, I believe the former.
Go to this URL site for data on the LM317
3 term regulator...:
http://www.national.com/ads-cgi/viewer.pl/ds/LM/LM117.pdf
Go to page 14 on the data sheet, the second circuit down on the left is for a constant current source up to an amp. The 1.2 ohm series
current limiting resistor would need to be scaled up for less current ...viz... ~12 ohm for ~100ma or ~120 ohm for ~10 ma.The 2 watt rating is needed for the 1 amp range and a heat sink would be neeeded on the device for an amp output..This is considering the need of a fixed Con/Curr value. The top of the page circuit gives you the option of an adjustable voltage as well as the current limiting UP TO the adjusted value.
Edd

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