Question
Download Solution PDF________ makes LEDs radiate red or yellow light.
Answer (Detailed Solution Below)
Detailed Solution
Download Solution PDFLED (light-emitting diode):
The LED (light-emitting diode) is a PN junction device that emits light when a current passes through it in the forward direction.
Materials used:
Semiconductor materials used for the manufacture of LED are gallium arsenide phosphide (GaAsP) which emits red or yellow light or gallium arsenide (GaAs) which gives green or red-light emission.
|
Semiconductor material |
Wavelength |
Colour |
|
GaAs |
850 – 940 nm |
Infra-red |
|
GaAsP |
630 – 660 nm |
Red |
|
GaAsP |
605 – 620 nm |
Amber |
|
GaAsP:N |
585 – 595 nm |
Yellow |
|
AlGaAs |
550 – 570 nm |
Green |
|
SiC |
430 – 505 nm |
Blue |
|
GaInN |
450 nm |
White |
Applications:
LEDs are used extensively in segmental and dot matrix displays of numeric and alphanumeric characteristics. Several LEDs are used in series to form one segment while a single LED may be used as a decimal point.
Advantages:
Size: LEDs are miniature in size and they can be stacked together to form numeric and alphanumeric displays in the high-density matrix.
Efficiency: LEDs have high efficiency as emitters of electromagnetic radiation.
Power consumption: They require moderate power for their operation. A typical voltage drop of 1.2 V and a current of 20 mA is required for full brightness. Therefore, LEDs are useful where miniaturization of DC power is important.
Available colors: LEDs are available in different colors like red.
Operating temperature:LEDs are rugged and can, therefore, withstand shocks and vibrations. They can be operated over a wide range of temperature 0 to 70°.
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