Adjustable Low Current Power Source. Need schematic.

[Rory Starkweather]

I need to build a low voltage (Maybe 3.3 VDC) Low current source to test/calibrate some D'arsonvalle milliameters. It needs to be able to provide a stable output current of between 0 and 100 mA.

Does anyone have a circuit, or a link?

 

[Arouse1973]

How about this one?
http://cds.linear.com/docs/en/datasheet/3092fb.pdf
Adam

 

[MrBretten]

The LM317 is a dirt cheap, widely used voltage/current regulator. The datasheet has lots of regulation circuits you can tweak to your needs: http://www.ti.com/lit/ds/symlink/lm117.pdf check out page 21; just adjust the potentiometers to your needs

 

[Arouse1973]

The LM317 is a dirt cheap, widely used voltage/current regulator. The datasheet has lots of regulation circuits you can tweak to your needs: http://www.ti.com/lit/ds/symlink/lm117.pdf check out page 21; just adjust the potentiometers to your needs

Yes but the control for current comes from the series resistor which carries load current This is ok for a battery charger but for calibration is it good enough, no I dont think so.
Adam

 

[Bluejets]

Then one needs a solid reference to calibrate the calibrator.

 

[Arouse1973]

Then one needs a solid reference to calibrate the calibrator.

Yes it called a calibrated multimeter.
Adam

 

[MrBretten]

Adam, you're probably right. Still, it's a pretty badass circuit

 

[Arouse1973]

Adam, you're probably right. Still, it's a pretty badass circuit

Yes I have used this circuit many times, you right it makes a good general purpose current source. But the resistor that controls the output current should not be in the current loop. Thats just my opinion. But others seem to think otherwise, why am I not supprised
Cheers Adam

 

[Rory Starkweather]

How about this one?
http://cds.linear.com/docs/en/datasheet/3092fb.pdf
Adam

Purrfect. TY

 

[Rory Starkweather]

The LM317 is a dirt cheap, widely used voltage/current regulator. The datasheet has lots of regulation circuits you can tweak to your needs: http://www.ti.com/lit/ds/symlink/lm117.pdf check out page 21; just adjust the potentiometers to your needs

I've been looking at the LM317 as well, but it is a linear regulator with all the efficiencies I've seen that go along with that.

The LT3902 might be a little more expensive, but it only requires 2 external parts.