Diodes are electronic components that allow current to flow in only one direction. They have two terminals called an anode and a cathode. Diodes have many applications including rectifying AC to DC current, over-voltage protection, logic gates, radiation detection, temperature measurement, and current steering. Common types of diodes include light emitting diodes (LEDs), avalanche diodes, laser diodes, Zener diodes, and rectifier diodes.

1. Semiconductor Diode

2. DiodeIt is an electronic device that ideally conducts in only one direction.

3. Actual FeaturesLegLegAnodeCathode

4. Electrical Symbol

5. PN Junction of DIODEIn N- Type material, The electron is called majority carrier and hole is minority carrier.

6. In P- type material, the electron is called minority carrier and hole is majority carrier.Internal Junction of DIODENPElectronsHoleDepletion RegionMetal Contact

7. Diode ApplicationsRadio demodulationThe first use for the diode was the demodulation of amplitude modulated (AM) radio broadcasts. The history of this discovery is treated in depth in the radio article

8. Power conversionRectifiers are constructed from diodes, where they are used to convert alternating current (AC) electricity into direct current (DC).

9. Over-voltage protectionDiodes are frequently used to conduct damaging high voltages away from sensitive electronic devices.

10. Logic gatesDiodes can be combined with other components to construct AND and OR logic gates. This is referred to as diode logic.

11. Ionizing radiation detectorsIn addition to light, mentioned above, semiconductor diodes are sensitive to more energetic radiation.

12. Temperature measurementA diode can be used as a temperature measuring device, since the forward voltage drop across the diode depends on temperature, as in a Silicon band gap temperature sensor.

13. Current steeringDiodes will prevent currents in unintended directions. To supply power to an electrical circuit during a power failure, the circuit can draw current from a battery.

14. Types of DiodesLight Emitting Diode (LED) It is one of the most popular type of diodes and when this diode permits the transfer of electric current between the electrodes, light is produced.

15. Avalanche DiodeThis type of diode operates in the reverse bias, and used avalanche effect for its operation. Generally, the avalanche diode is used for photo-detection, wherein high levels of sensitivity can be obtained by the avalanche process.

16. Laser DiodeThis type of diode is different from the LED type, as it produces coherent light. These diodes find their application in DVD and CD drives, laser pointers, etc. Laser diodes are more expensive than LEDs.

17. ZenerdiodeThis type of diode provides a stable reference voltage, thus is a very useful type and is used in vast quantities. The diode runs in reverse bias, and breaks down on the arrival of a certain voltage.

18. Rectifier DiodeThese diodes are used to rectify alternating power inputs in power supplies. They can rectify current levels that range from an amp upwards. If low voltage drops are required.