What are Rectifiers?

A rectifier is an electrical device that converts Alternating Current (AC) into Direct Current (DC) by using one or more P-N junction diodes.

When a voltage is applied on the P-N junction diode in a way that the positive terminal (+ve) of the battery is connected to the P-type semiconductor and the negative terminal(-ve) of the battery and is connected to the N-type semiconductor called forward biased. When the forward bias voltage is applied to the P-N junction diode the large number of free electrons (e-) (majority carriers) in the N-type semiconductor experiences a repulsive force from the negative terminal of batter and similarly, the large number of holes(majority carriers) in the p-type semiconductor experiences a large repulsive force from the positive terminal of the battery.

As a result, the free electron in the N-type semiconductor moves from the N-side to the P-side and as such the holes in the P-type semiconductor start to move from the P to the N-side. As we know the current means flow of charges (free electrons and holes). So, the flow of the electrons from the N-side to the P-side and the holes flow from the P to the N side which conduct electric current. The maximum number of carriers produces the electric current in the forward bias. So the current produced in the forward bias is also called majority current.

When the voltage is applied to the P-N junction diode in such a manner that the positive terminal of the battery is connected to the N-type and the negative terminal of the battery is connected to the P-type then the diode is reverse biased.

So when this reverse bias voltage is applied to the P-N junction diode, the large of free electrons in the N-type experience an attractive force from the positive terminal of the battery, in the same manner, a large number of holes in the P-type experience an attractive force from the negative terminal of the battery.

As a result of reverse bias the free electrons in the N-type semiconductor move away from the P-N junction and are attracted to the positive terminal of the battery. At the same, the holes in the P-type move away from the P-N junction and are attracted to the negative terminal of the battery. The electric flow does not occur across the P-N junction. The minority carrier in the P-type experiences a repulsive force from the negative terminal of the battery and as same the minority carrier in the N-type experiences a repulsive force from the positive terminal of the battery. As a result, the minority carriers free electrons in the P-type semiconductors and the minority carriers holes in the N-type start flowing in the junction. The electric current is produced by the minority carriers in very small. So the minority carrier current in the reverse bias is neglected.

The P-N junction allows the current in the forward bias and blocks the current in the reverse bias. In simple words the P-N unction allows electric current in one direction only. This unique property of the diode allows it to behave like a rectifier.

A Rectifier is an electronic device that converts the alternating current (AC) into direct current (DC) by allowing a current to flow through the device in one direction only using one or more P-N junction diodes. Many circuits use DC voltage for operation. It can easily convert AC voltage or current into DC or voltage. A P-N junction diode allows the current to flow in a forward bias condition and blocks the current in a reverse bias condition. More simply we can say that a diode allows electric current to flow in a single direction. This property of the diode allows it to act as a rectifier and the process is called rectification.