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Transmitters Light emitting diode (LED) in electronics a semiconductor device that emits infrared or visible light when charged with an electric current. Visible LEDs are used in many electronic devices as indicator lamps, in automobiles as rear-window and brake lights, and on billboards and signs as alphanumeric displays or even full-color posters. Infrared LEDs are employed in autofocus cameras and television remote controls and also as light sources in fiber-optic telecommunication systems.
The familiar light bulb gives off light through incandescence, a phenomenon in which the heating of a wire filament by an electric current causes the wire to emit photons, the basic energy packets of light. LEDs operate by electroluminescence, a phenomenon in which the emission of photons is caused by electronic excitation of a material. The material used most often in LEDs is gallium arsenide, though there are many variations on this basic compound, such as aluminum gallium arsenide or aluminum gallium indium phosphide. These compounds are members of the so-called III-V group of semiconductors—that is, compounds made of elements listed in columns III and V of the periodic table. By varying the precise composition of the semiconductor, the wavelength (and therefore the color) of the emitted light can be changed. LED emission is generally in the visible part of the spectrum (i.e., with wavelengths from 0.4 to 0.7 micrometer) or in the near infrared (with wavelengths between 0.7 and 2.0 micrometers). The brightness of the light observed from an LED depends on the power emitted by the LED and on the relative sensitivity of the eye at the emitted wavelength. Maximum sensitivity occurs at 0.555 micrometer, which is in the yellow-orange and green region. The applied voltage in most LEDs is quite low, in the region of 2.0 volts; the current depends on the application and ranges from a few mill amperes to several hundred-mill amperes.
The term diode refers to the twin-terminal
The familiar light bulb gives off light through incandescence, a phenomenon in which the heating of a wire filament by an electric current causes the wire to emit photons, the basic energy packets of light. LEDs operate by electroluminescence, a phenomenon in which the emission of photons is caused by electronic excitation of a material. The material used most often in LEDs is gallium arsenide, though there are many variations on this basic compound, such as aluminum gallium arsenide or aluminum gallium indium phosphide. These compounds are members of the so-called III-V group of semiconductors—that is, compounds made of elements listed in columns III and V of the periodic table. By varying the precise composition of the semiconductor, the wavelength (and therefore the color) of the emitted light can be changed. LED emission is generally in the visible part of the spectrum (i.e., with wavelengths from 0.4 to 0.7 micrometer) or in the near infrared (with wavelengths between 0.7 and 2.0 micrometers). The brightness of the light observed from an LED depends on the power emitted by the LED and on the relative sensitivity of the eye at the emitted wavelength. Maximum sensitivity occurs at 0.555 micrometer, which is in the yellow-orange and green region. The applied voltage in most LEDs is quite low, in the region of 2.0 volts; the current depends on the application and ranges from a few mill amperes to several hundred-mill amperes.
The term diode refers to the twin-terminal