Rectifier

In Electricity, we have learnt that the mains supply at our home is an a.c supply, but many appliances require a d.c to function properly. Therefore, we have to convert a.c to d.c and this conversion is called rectification. It is done by using a diode.

Recall that the diode is a semiconductor that allows current to flow in one direction only. 

Types of Rectification

(1) Half Wave Rectification

This can be simply done by using a diode.
V1 is input a.c supply;
VR is the p.d across resistor R.
Explanation:

At time intervals 0 to 1 and 2 to 3, the diode is forward biased and hence there is a current flowing in R, which give rise to an output voltage VR.

At time intervals 1 to 2 and 3 to 4, the diode is reverse biased and hence no current flowing in R, thus VR = 0.
(2) Full Wave Rectification

This can be done by using four diodes connected in a bridge format.
At time interval 0 to 1 and 2 to 3, when A is positive with respect to F, diode D2 and D4 are forward biased while D1 and D3 are reverse biased. The current will flow in the direction of ABCDEF, which giving rise to an output voltage VR.

At time interval 1 to 2 and 3 to 4, when A is negative with respect to F, diode D1 and D3 are forward biased while D2 and D4 are reverse biased. The current will flow in the direction of FECDBA, which again giving rise to an output voltage VR.

We can see that the current flowing through the resistor R is in the same direction (always from C to D), thus the output voltage VR is in the same direction as shown in the waveform.

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