What is rectifier ? Explain the working of junction diode as a full wave rectifier, with diagram.

Explanation

Rectifier: It is device which can convert alternating current into direct current.
Principle: The working of a rectifier is based on the principle that p-n junction diode conducts when forward biased and does not conduct when reverse biased.
Arrangement: Circuit diagram of a full wave rectifier is shown in Figure. It consists of a step down transformer consisting of the coils PP and SS, two junction diodes `D_(1) and D_(2)` and a load resistance `R_(L)`. The ends of secondary coil SS of the transformer are connected to the p-region of the diodes. N-region of both the diodes are connected to the centre of the secondary coil of the transformer through the load resistance `R_(L)`. Working : During the first half cycle of input signal, S being at positive potential, `D_(1)` is forward biased and `D_(2)` is reverse biased. `D_(1)` offers low resistance to the charge carriers whereas `D_(2)` offers very high resistance to charge carriers. Therefore forward current flows in `D_(1)` due to majority charge carriers. During the next half cycle of the input a.c. signal, `D_(1)` gets reverse biased and `D_(2)` gets forward biased.

So, now the current flows through `D_(2)` due to majority charge carriers. In this way, during both half cycles the current flows through `R_(L)` in the same direction, so we get a unidirectional -varying d.c. voltage across `R_(L)`. Since voltage is obtained for both the half cycles of the input a.c. signal, hence we get full wave rectified. The input signal and output signal are shown in Figure above. Since output is pulsating and unidirectional it contains ripples, i.e., d.c. and a.c. components. To make it pure d.c., filter circuits can be used