An ideal P-N junction diode is of two terminal polarity sensitive device that has zero resistance ( i.e diode conducts)when it is forward biased and infinite resistance( i.e diode does not conduct) when reverse biased. Because of this property the diode finds use in many applications as enumerated below:
1. As rectifier in dc power supplies.
2. In demodulation or detector circuits.
3. In clamping networks employed as dc restorers in TV receivers and voltage multipliers.
4. In clipping circuits used as wave shaping circuits in computers, radars, radio and TV receivers.
5. As switches in digital logical circuits.
The same PN junction with different doping concentrations finds special applications as follows:
1. As zener diodes in voltage regulators, peak clippers, in switching operation.
2. As tunnel diodes as a relaxation oscillator at microwave frequencies.
3. As light emitting diodes(LEDs) in digital displays.
4. As LASER diodes in optical communications.
5. As varactor diodes in tuning sections of radio and TV receivers.
6. As detectors(PIN photodiode) in optical communication circuits.