A rectifier is a device which converts a.c. voltage to pulsating d.c. voltage, using one or more p-n junction diodes.
The p-n junction diode conducts only in one direction. It conducts when
forward biased while practically it does not conduct when reverse
biased. Thus if an alternating voltage is applied across a p-n junction
diode, during positive half cycle the diode will be forward biased and
will conduct successively. While during the negative half cycle it will
be reversed biased and will not conduct at all. Thus the conduction
occurs only during positive half cycle. If the resistance is connected
in series with the diode, the output voltage across the resistance will
be unidirectional i.e. d.c. Thus p-n junction diode subjected to an a.c.
voltage acts as a rectifier converting alternating voltage to a
pulsating d.c. voltage.
