What is a Diode? How does a diode work?

Diode definition is that diodes are semiconductor elements and are part of almost every electronic circuit. The main characteristic of a diode is that allows the current flow in one direction only, so they act as a valve and are used to convert AC into DC.

Symbol of Diode - The symbol of a diode is shown in video

How does a diode work - Diode working principle is that a diode allows current to flow only when + terminal of DC voltage source is connected to anode and - terminal is connected to cathode and in that case diode is FORWARD BIASED or OPEN.
If voltage source is connected in opposite direction diode do not allow current to flow and diode is REVERSE BIASED or CLOSED

what is a diode made of - Diodes are made of materials called semiconductors such as Silicon and Germanium.
Silicon has a crystalline structure. It has four vallence electrons forming vallence bonds. Atoms share these electrons and they are in vallence band and can not move free into the cristal. That is pure or intrinsic silicon. Adding impurities changes conductive properties of silicon. This process
is called doping. There are two types of impurities:
- Donors - have 5 electrons in outer shell (Phosphorus, Arsenic, Antimony, Bismuth, Lithium)
- Acceptors - have 3 electrons in outer shell (Boron, Aluminium, Nitrogen, Gallium, Indium)

2 types of semiconductors:
N-type: c with donors there are extra electrons that can move around.
P-type: Doping with acceptors electron is missing in vallence shell, we can observe as positivly charged hole.

PN Junction diode - PN Junction is formed when P-type and N-type semiconductors are put togather phisicaly.
There is a diffusion of electrons from N-type to P-type side of the junction. This creates positively charged region at N-type side and negatively charged region at P-type side. - When PN Junction is connected to voltage source (battery) there are two different situations:
1. N-type region (cathode) connected to negative pole of battery and P-type region (anode) connected to positive pole.
2. N-type region (cathode) connected to positive pole of battery and P-type region (anode) connected to negative pole.

Types of Diode:
- The types of diode are as follow-
- Zener diode
- P-N junction diode
- Tunnel diode
- Varactor diode
- Schottky diode
- Photo diode
- PIN diode
- Laser diode
- Avalanche diode
- Light emitting diode
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Create: Sasho Bozhinoski
Hrvoje Čočić
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Category: Education
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