Experiment 8 - Other Colored LEDs

Are there differences in characteristics between different colored LEDs?

To investigate this, use the yellow, green and blue LED and measure the forward voltage.

You will be surprised how great the differences are. Typical values for the forward voltage are... red: 2.0 Volt yellow: 2.1 Volt green: 2.2 Volt blue: 3.0 Volt

Circuit diagram voltage measurement of the colored LEDs.

Circuit measuring the forward voltage of a yellow LED. (Enlarge)

Circuit measuring the forward voltage of a green LED. (Enlarge)

Circuit measuring the forward voltage of a blue LED. (Enlarge)

Your actual measured values ​​may differ greatly from this. The forward voltage drop is determined by the used semiconductor material and this information you find only from data sheets.

                                                                                                                                                                                                                                                                                                                                                                                                                                                  

Color		ULED	Materials
infrared		< 1.9 V	GaAs, AlGaAs
red		1,6 - 2.0 V	AlGaAs, GaAsP, AlGaInP, GaP
yellow		2.1 - 2.2 V	GaAsP, AlGaInP, GaP
green		1.9 - 4.0 V	InGaN, GaN, GaP, AlGaInP, AlGaP
blue		2.5 - 3.7 V	ZnSe, InGaN, SiC

Forward voltages and materials used by common LEDs (Source: Wikipedia).