(a)

Explain the characteristics of a $\displaystyle \mathrm{p}-\mathrm{n}$ junction diode that makes it suitable for its use as a rectifier.

(b)

With the help of a circuit diagram, explain the working of a full wave rectifier.

A p-n junction diode allows current to pass only when it is forward biased.

When the input voltage to A with respect to the centre tap at any instant is positive, at that instant the voltage at B, being out of phase, will be negative; diode $\displaystyle D_{1}$ gets forward biased and conducts while $\displaystyle D_{2}$, being reverse biased, does not conduct. Hence during this half cycle an output current and output voltage across $\displaystyle R_{L}$ is obtained. During the second half of the cycle when the voltage at A becomes negative with respect to the centre tap, the voltage at B would be positive. Hence $\displaystyle D_{1}$ would not conduct but $\displaystyle D_{2}$ would, giving an output current and output voltage. Thus output voltage is obtained during both halves of the cycle.