Leakage current and LEDs

[Diver300]

This is just comment, there is no question to be answered, but further comments are welcome.

I was working with an LED (uk.farnell.com/1716701) on stripboard, and lighting the LED at extremely low duty cycles, just while testing. I was finding that the LED was glowing a bit when it was supposed to be off.

I soon realised that the brightness depended on how I was holding the board. The LED was lighting visibly with the leakage current through my fingers. I tested another one and it is clearly visible at 2 µA.

It's standard practice to put a resistor from base to emitter of a transistor to make sure that it doesn't turn on from leakage current. A 10 kΩ resistor in parallel fixed the problem, and I'll include one in future where there could be confussion.

 

[Diver300]

More LED fun

I took 2 more of those LEDs (uk.farnell.com/1716701) and connected them in parallel, anode to anode, but to nothing else.

When I held one under a bright light source, a few mm away from one of these uk.farnell.com/1761159 driven at about 140 mA, the LED that was in the dark glowed.

The voltage and current are about 1.6 V and 10 µA

The short circuit current of the illuminated LED was about 30 µA and the open circuit voltage is about 1.6 V

The readings are rather variable as they depend a lot on how well lined up the white LED and the LED used as a solar cell are.

 

[ronsimpson]

I have used LEDs to meause light. 1V at 10uA