Understanding LED (Light Emitting Diode) and its Working Principle

LEDs (Light Emitting Diode) is an electronic component that can emit monochromatic light when a forward voltage is applied. LED is a family of diodes made of semiconductor materials. The colors of the light emitted by an LED depend on the type of semiconductor material it uses. LEDs can also emit infrared rays that are invisible to the eye as we often encounter on TV Remote Control or Remote Control other electronic devices.

The shape of the LED is similar to a small bulb (light bulb) and can be easily attached to various electronic devices. Unlike incandescent lamps, LEDs do not require burning the filament so they do not generate heat to produce light. Therefore, the current LED (Light Emitting Diode) which is small in shape has been widely used as a lamp in LCD TVs instead of tube lamps.

LED Shapes and Symbols (Light Emitting Diode)

LED Shapes and Symbols (Light Emitting Diode)

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How LEDs Work (Light Emitting Diode)

As said earlier, LEDs are a family of Diodes made of Semiconductors. The way it works is almost the same as a diode which has two poles, namely the positive pole (P) and the negative pole (N). The LED will only emit light when a forward voltage (forward bias) is applied from the anode to the cathode.

LEDs consist of a semiconductor chip doped to create a P and N junction. What is meant by the doping process in semiconductors is the process of adding impurities to a pure semiconductor so as to produce the desired electrical characteristics. When the LED is powered by a forward voltage or forward bias, i.e. from the anode (P) to the cathode (K), the excess electrons in the N-type material will move to an area with an excess of holes, which is a positively charged region (P-type material). When an electron meets a hole, it releases a photon and emits monochromatic light (one color).

An LED or Light Emitting Diode that emits light when a forward voltage is applied can also be classified as a Transducer that can convert Electrical Energy into Light Energy.

How to Find the Polarity of the LED

To determine the polarity of the anode (+) and cathode (-) terminals on the LED. We can see it physically based on the picture above. The characteristics of the Anode Terminal on LEDs are the longer legs and also the smaller Lead Frame. While the characteristics of the Cathode Terminal are shorter legs with a large Lead Frame and are located on the flat side.

LED (Light Emitting Diode) colors

Currently, LEDs have various colors, including red, yellow, blue, white, green, orange and infrared. The color diversity of the LEDs depends on the wavelength and the semiconductor compounds used. The following is a table of semiconductor compounds used to produce color variations in LEDs:

Semiconductor Material Wavelength Color
Gallium Arsenide (GaAs) 850-940nm Infrared
Gallium Arsenide Phosphide (GaAsP) 630-660nm Red
Gallium Arsenide Phosphide (GaAsP) 605-620nm Orange
Gallium Arsenide Phosphide Nitride (GaAsP:N) 585-595nm Yellow
Aluminum Gallium Phosphide (AlGaP) 550-570nm Green
Silicon Carbide (SiC) 430-505nm Blue
Gallium Indium Nitride (GaInN) 450nm White

Forward Biased Voltage Each Color LED (Light Emitting Diode) requires a forward voltage (Forward Bias) to turn it on. The forward voltage for the LED is relatively low so it requires a resistor to limit the current and voltage so as not to damage the LED in question. Forward Voltage is usually denoted by the sign VF.

Color Forward Voltage @20mA
Infrared 1.2V
Red 1.8V
Orange 2.0V
Yellow 2.2V
Green 3.5V
Blue 3.6V
White 4.0V


Uses of LEDs in Daily Life

LED technology has various advantages, such as it does not generate heat, is durable, does not contain hazardous materials such as mercury, and saves electricity and its small size is becoming increasingly popular in the field of lighting technology. Various products that require light also adopt this Light Emitting Diode (LED) technology. The following are some of the applications of LEDs in everyday life.

  1. Home Lighting Lampu
  2. Street Lighting
  3. Billboard (Advertising)
  4. Backlight LCD (TV, Mobile Display, Monitor)
  5. Interior and Exterior Decoration Lights
  6. Indicator Light
  7. Infrared Transmitter on Remote Control (TV, AC, AV Player)

That’s the definition of LED and how it works, hopefully it’s useful.

Source : https://teknikelektronika.com/