LM334s are made to sink or source a certain amount of current that is set with 1 resistor.

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Diagram:

Video below demonstrates how to use the LM334 on a breadboard.





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Video

Quick LM334 three terminal adjustable constant current source circuit schematic to breadboard build



Main points:

Resistance is used to set the amount of current that flows through the LM334 as long as there is enough voltage to power everything connected in series with it. All series components pass the same current, so that becomes the current through them as well.

Datasheet says that 0.064V (64mV) is set across the resistor from pin R to V- pin in order to set the current. It seems like the ones I’ve used actually set 0.068V (68mV) across the resistor based on the current that I have been getting.

Exact current still varies a bit with temperature. Covered in more detail on the component’s datasheet.

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