what is pn junction diode and its working
A P-N junction diode is a semiconductor device. It is formed by combining P-type and N-type semiconductors together. It has contacts (or leads) for providing external voltage. It is a two terminal device.
According to the polarity of the applied voltage, the diode may be working in forward biased condition, or in reverse biased condition. If the positive terminal of the external supply is connected to the P side and negative terminal to the N side, then the diode is said to be in forward biased condition. The width of the depletion layer decreases and the diode conducts easily. When the P side of the diode is connected to the negative terminal and N side to the positive terminal of the supply, the diode is said to be in reverse biased condition. The width of the depletion layer increases and the diode offers very high resistance at this condition.
Diodes are widely used for rectification purpose. Other uses are as detectors in radio receivers, voltage regulators (zener diode), Lighting (LED), Remote control (Infra red LED) etc.