Explain the use of junction diode as a full wave rectifier by drawing circuit diagram and draw the form of input and output waves.

Explanation

The full wave rectifier is made of a transformer, two junction diode `D_(1) and D_(2)` and a load resistance `R_(L)`.

The primary coil of the transformer is connected to the a.c. supply. The p-side of the two diodes are connected to the ends of the secondary of the transformer and both diodes are connected to the centre tap of the secondary by attaching the n-sides to the load resistance `R_(L)`.
Each diode works only during half of the full cycle of a.c. simultaneously, and therefore during the full cycle of a.c. between the two ends of load resistance `R_(L)`, the current obtain in one direction which is called rectified (unidirectional) current.
Full wave rectification can also be obtained using four junction diodes, which does not required a centre tap in the secondary.
The voltage at B becomes positive during a.c. cycles when the voltage at A relative to the centre tap becomes negative so current does not flow from `D_(1)` (due to reverse bias) but current flow from `D_(2)` (due to forward bias) and current flow from load resistance `R_(L)` in X to Y direction.
And when the diode A becomes forward bias and B becomes reverse bias during a.c. cycle, the current does not flow from diode B but current is flow in A so the current flows from load resistance `R_(L)` in the X to Y direction.
Hence, current flows from both diode simultaneously occur during the subsequent a.c. cycle hence flows load resistance in one direction so D.C. voltage across the resistance is obtained.
The input of both diode and the output waveform obtain from `R_(L)` in full wave rectifier is shown in below figure (c ).

The efficiency of a full wave rectifier is higher than the efficiency of a halfwave rectifier.