LED Forward Voltages

Forward voltage rises with photon energy, so blue and white LEDs need roughly twice the headroom of a red one — a 3.3 V rail cannot reliably drive a blue LED with a series resistor.

Colour	Wavelength (nm)	Typical Vf (V)	Typical If (mA)
Infrared	850–940	1.2 – 1.6	20 – 100
Red	620–645	1.8 – 2.2	20
Amber	600–612	1.9 – 2.2	20
Yellow	585–595	2.0 – 2.4	20
Green (std)	565–570	2.0 – 2.4	20
Green (pure/InGaN)	520–535	3.0 – 3.6	20
Blue	460–475	2.8 – 3.6	20
White	broadband	2.8 – 3.6	20 – 350
UV	390–410	3.1 – 4.4	20

Vf varies by part, bin and current — always use the datasheet value. Size the resistor with the LED Series Resistor tool.

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