Browse Definitions:

light-emitting diode (LED)

Also see laser diode.

A light-emitting diode (LED) is a semiconductor device that emits visible light when an electric current passes through it. The light is not particularly bright, but in most LEDs it is monochromatic, occurring at a single wavelength. The output from an LED can range from red (at a wavelength of approximately 700 nanometers) to blue-violet (about 400 nanometers). Some LEDs emit infrared (IR) energy (830 nanometers or longer); such a device is known as an infrared-emitting diode (IRED).

An LED or IRED consists of two elements of processed material called P-type semiconductors and N-type semiconductors. These two elements are placed in direct contact, forming a region called the P-N junction. In this respect, the LED or IRED resembles most other diode types, but there are important differences. The LED or IRED has a transparent package, allowing visible or IR energy to pass through. Also, the LED or IRED has a large PN-junction area whose shape is tailored to the application.

Benefits of LEDs and IREDs, compared with incandescent and fluorescent illuminating devices, include:

  • Low power requirement: Most types can be operated with battery power supplies.

  • High efficiency: Most of the power supplied to an LED or IRED is converted into radiation in the desired form, with minimal heat production.

  • Long life: When properly installed, an LED or IRED can function for decades.

Typical applications include:

  • Indicator lights: These can be two-state (i.e., on/off), bar-graph, or alphabetic-numeric readouts.

  • LCD panel backlighting: Specialized white LEDs are used in flat-panel computer displays.

  • Fiber optic data transmission: Ease of modulation allows wide communications bandwidth with minimal noise, resulting in high speed and accuracy.

  • Remote control: Most home-entertainment "remotes" use IREDs to transmit data to the main unit.

  • Optoisolator: Stages in an electronic system can be connected together without unwanted interaction.

This was last updated in September 2005

Join the conversation


Send me notifications when other members comment.

By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy

Please create a username to comment.

hi nyc
Q: Now LED lights are recommended for most office lighting as downlighter. Are those LED light are the same as defined here in electronics ? gk
If a dimmable switch is used with LED's does their life expectancy extend beyond the specification or does it matter.
LEDs for house lighting is one of the great tech innovation of the last 10 years (I would argue beating the iPhone!) as it LEDs turn 50% of energy into light comapred to 4% of energy with incandescent bulbs!
Very good! It's helpful information. I'm really happy to know.


File Extensions and File Formats

Powered by:


  • risk map (risk heat map)

    A risk map, also known as a risk heat map, is a data visualization tool for communicating specific risks an organization faces. A...

  • internal audit (IA)

    An internal audit (IA) is an organizational initiative to monitor and analyze its own business operations in order to determine ...

  • pure risk (absolute risk)

    Pure risk, also called absolute risk, is a category of threat that is beyond human control and has only one possible outcome if ...


  • federated identity management (FIM)

    Federated identity management (FIM) is an arrangement that can be made among multiple enterprises to let subscribers use the same...

  • cross-site scripting (XSS)

    Cross-site scripting (XSS) is a type of injection security attack in which an attacker injects data, such as a malicious script, ...

  • firewall

    In computing, a firewall is software or firmware that enforces a set of rules about what data packets will be allowed to enter or...




  • all-flash array (AFA)

    An all-flash array (AFA), also known as a solid-state storage disk system, is an external storage array that uses only flash ...

  • volume manager

    A volume manager is software within an operating system (OS) that controls capacity allocation for storage arrays.

  • external storage device

    An external storage device, also referred to as auxiliary storage and secondary storage, is a device that contains all the ...


  • hybrid hard disk drive (HDD)

    A hybrid hard disk drive is an electromechanical spinning hard disk that contains some amount of NAND Flash memory.