Building a current source with LM234

Thread Starter

Lupon

Joined Jan 1, 2020
2
Hello everyone.

I want to build a current source for low currents, 1-5mA. I've searched for something easy and found the LM234. In his datasheet there are an application to build an independent temperature current source (pg 6). I've simulated in Pspice with this model for the LM334, and work. (see atached images)
Pspice sim circuit.png
Pspice sim result.png

So i've decided to try implement. (see atached images)
Circuit_low.png
VCC it's 5V.

But when i've mounted in a protoboard, don't work. If i change the load, current across the load (potentiometer) change. Anyone know what i misunderstanding?
 

Attachments

AlbertHall

Joined Jun 4, 2014
9,024
As you increase the load resistance you will eventually reach the point where there isn't enough voltage left for the current source to work properly.
What is the supply voltage?
 

Thread Starter

Lupon

Joined Jan 1, 2020
2
Resistance ranges from 0 to 2k. Voltage is 5,2 volts approx, taken from a ATX PSU. In addition i tried 5 volts from Arduino Uno. In both cases similar result.

There isn't linear zone. If i change resistance with potentiometer, change intensity. With very low values i get even more than 100mA. Attach a graph with some random values that i taken:
untitled.png
 
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