In current market, Infrared LED main wavelength are 850nm and 940nm. There are also some other wavelength , like 740nm, 810nm, and far infrared wavelength 1050nm, 1250nm. But these infrared wavelengths are seldom used on electronics, the common infrared wavelength used on electronics are 850nm and 940nm. Do you know the differences between IR 850nm and 940nm ?

1. 850nm and 940nm both are Infrared lights, and unit is “nm”, they are the lights emitted from chips, but different wavelength.

2. Generally, at the same forward current , the higher wavelength, the lower forward voltage it will be. For example, current=20mA, the forward voltage of 850nm IR LED is 1.35-1.55v; but forward voltage of 940nm is 1.10-1.25v..  Of course, forward voltage is different at different working current.

3. When 850nm IR LED is working, you can see there’s a small “red dot”in the chip, but 940nm IR LED light not such a visible “red dot”when it’s working. Some customers use black casing LED to cover up the “red dot”if they don’t want to see that it , but it’s still can be seen if you look at it carefully.

4. The radiation intensity of 850nm is two or three times of 940nm, the higher radiation intensity, the higher brightness.

5. When test 850nm IR LED and 940nm IR LED, you can drive 850nm IR LED by a 1.5v battery to judge it light up or not, but for 940nm, you need to use mobile phone or camera to judge it light up or not.

6. At the same forward current, forward voltage of 940nm is lower than 850nm, the power dissipation is also lower. So, if use the same size chip for 850nm and 940nm 3mm through-hole LED, the chip of 940nm can bear bigger forward current than 850nm chip.

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