Color and voltage of LEDs © Siemens Stiftung 2018 CC BY-SA 4.0 international

Color and voltage of LEDs


The operating voltage of LEDs depends on the color. This is an indication of discrete energy levels and the photon character of light.

English, Spanish (CREA), German
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What color an LED emits depends on the energy level of the charge transition from the non-conduction band to the conduction band. Depending on the basic material (Si, GaAs, GaN etc.) and doping, as well as the internal resistance every LED has a typical operating voltage (voltage = potential = energy difference). Although this is modified by the design (internal resistance, etc.), in the final analysis it is determined by the discrete energy level of the charge transition between non-conduction and conduction band.

Information and ideas:
The abstract principle of the quantization of energy in the form of photons is demonstrated clearly in an extremely simple experiment with four LEDs and a power supply unit. Red LEDs light up at a voltage from about 1.5 volts, yellow from about 1.9 volts, green from about 2.3 volts and blue from about 3.3 volts.
Instructions for building a variable LED color mixer can be found in the experimentation instructions “Experiments – energy quantization with LEDs" on the media portal of the Siemens Stiftung.
There are no other media directly related to this file.
Physics; Technology
Grade 5 to 6; Grade 7 to 9; Grade 10 to 13
Middle/high school
Color Theory; Light; Semiconductor; Wave (physics); Color formation; Electroluminescence; Light generation; Light-emitting diode (LED); Wave (physics)
Siemens Stiftung Media Portal
MediaHouse GmbH
© Siemens Stiftung 2018
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