Semiconductors - Diode

We must have played with a remote car

Even though the remote is at a distance from the car, still it can control it.

The reason behind it is the diode.

Let’s learn about semiconductor diodes.

A semiconductor-diode is basically a p-n junction with metallic contacts provided at the ends.

The ends are provided for the application of an external voltage.

It is a two-terminal device represented symbolically as above,

The direction of the arrow represents the conventional direction of the current.

The two terminals of the diode are cathode and anode.

An anode is a positive terminal and Cathode is a negative terminal.

We can have semiconductor diode connected to a circuit in two ways namely, Forward biased and Reverse biased.

Let’s begin with Forward bias

When the positive side of the battery is connected to anode and negative to the cathode, It is said to be forward-biased.

In forward biased connection, the resistance is very low or negligible.

Here we learn about Reverse bias

When the negative side of the battery is connected to anode and positive to the cathode, It is said to be reverse biased.

In reverse biased connection, the resistance is very high.

Let’s discuss the V-I characteristics of p-n junction diode in forward bias

The graph shows the V-I characteristics of the p-n junction diode

In forward bias, the current increases very slowly till the voltage reach certain value.

After that voltage, the current increases exponentially even for a small increase in voltage.

This voltage is known as threshold voltage or cut-in voltage.

Now we will see the same for reverse bias

After crossing certain voltage in reverse bias, the current suddenly rises.

This voltage is called breakdown voltage.

Here we discuss the working of Light-emitting diode

A light-emitting diode(LED) is a heavily doped p-n junction that under forwarding bias emits spontaneous radiation.

When the LED is forward biased recombination of the minority and majority carriers takes place near the junction.

On recombination, energy is released in the form of photons.

Revision

A semiconductor-diode is basically a p-n junction with metallic contacts provided at the ends.

It can be connected in 2 ways, 1- Forward bias 2- Reverse bias

The graph shows the V-I characteristics of the p-n junction diode

A light-emitting diode(LED) is a heavily doped p-n junction that under forwarding bias emits spontaneous radiation.

The End