Light Emitting Diode

Light emitting diodes are none other than the highest widely used standard source of light in electrical equipment. For instance, they are extensively made for use in devices for showing what is the time or different types of data on displays. In this post, the main focus would be on learning a lot about LED.

What is a LED?

A light releasing diode is none other than an electric component that would emit light when the current of electricity would be passing through it.

Light Emitting Diode Symbol

The figure demonstrates the LED symbol: this would be somewhat similar to p-n junction diode where the only change would be that the two arrows would indicate that the diode would emit the light.

Following is the table explaining the links related to LED:

Light Emitting Diode Circuit

The LEDs also have a specific drop in voltage forward in cases where it is used normal circuits like a conventional diode. The drop in voltage depends on the current of LED, the color of the produced light, etc. There are different values in the drop of voltage that would vary from 1.5V to 2.5 V current for 10 to 50 mA current.

LED Basic Operation

The holes lie in the valence band and the free electrons are placed in the conduction band. When there is a forward bias in the p-n junction, the electron which is a part of the n-type semiconductor material would overrun the p-n junction and join with the holes in the p-type semiconductor material. Therefore regarding the holes, the free electrons would be at the higher energy bands.

The figure demonstrates the elementary process principle.

When there is a recombination of free electrons at the hole,  there would be a change regarding the energy level concerned from a value that is higher to the value that is lower and it drops from the conduction band to the valance band.  There is a release of energy due to the motion of electron. In standard diodes, the release of energy in the manner of heat. But in LED the release of energy in the form of photons that would emit the light energy. The entire process is termed as electroluminescence and the diodes are termed as light emitting diode.

In LED, energy discharged in light form hinges on the forbidden energy gap. One could manipulate the wavelength of the light produced. Therefore, the light color and its visibility or not, could be controlled from its wavelength. The color and wavelength of the light emitted can be determined by doping it with several impurities.

Practise This Question

Two springs A and B have force constants k1 and k2 respectively. The ratio of work done on A to that done on B when they are stretched by the same force is