LED - Light Emitting Diode
PN junction using gallium arsenide or gallium phosphide releases photons or light energy when electric energy is applied across it. PN-diode having such a properly is called as Light Emitting Diode (LED).
- When forward bias applied across the gallium arsenide/phosphide PN junction, the electrons from N type injected into P type through PN junction.
- These free electron from N type recombine with majority holes is P type.
- The light energy will be released, due to recombination of electrons and holes.
- This is due to the light emissive nature of gallium arsenide/phosphide.
- The intensity of light is proportional to the applied forward bias.
LCD: Liquid Crystal Display
The Liquid Crystal display consists of a thin layer of normally transparent liquid crystal material between two electrodes.
When an electric field is applied (15V to 60V), the material becomes turbulent, reflecting and scattering ambient light.
LED vs LCD:
|LEDs Consume more power than LCDs.||LCD Consumes very less power.|
|Due to high power requirement, LED requires external interface circuits (called as LED Driver Circuit) when driven from ICs.||LCD can be driven directly from IC chips. Driver Circuits are not required.|
|The brightness level is very good for LEDs||LCDs have moderate brightness level.|
|Commercially available LEDs have operating temperature range of -40 to 85 degree celcius.||comparatively less temperature limit. The temperature range is limited to -20 to 60 degree celcius.|
|Life time is around 1,00,000 hours||Due to chemical degradation the life time is 50,000 hours.|
|LEDs have wide viewing angle.|
The viewing angle is 150 degree
|The viewing angle for LCD is 100 degree|
|Operating voltage range is 1.5V to 5VDC.||Operating voltage range is 3 to 20 VDC.|