Conductors: such as copper, silver, gold and iron are good materials that allow the flow of electrons through them.
Insulators: such as wood, plastic, rubber and glass are materials that do not allow electrons to flow through them.
Semiconductors such as silicon and germanium are neither good conductor nor good insulators.
A new material that is based on semiconductors is produced by combining two materials in a certain ratio that will have a controllable behavior different than conduct/insulate.
The Diode is the simplest device that makes use of semiconductors and are the base of a very complicated devices such as transistors, Integrated Circuits, Microprocessors.
The idea behind Diodes is that they can control the flow of electrons through them to one direction only. This is achieved by process called biasing.
There are two types of diode biasing, forward and reverse. Forward biasing allow the diode in a circuit to conduct and allow electrons to flow in one direction.
However, when the diode is reverse biased it will work as an insulator and prohibit electrons from flowing through it.
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| Reverse Biasing a Diode, No Current flow |
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| Forward Biasing a Diode, Current Flows in Circuit |
The behavior of a diode in a circuit is very similar to a one way valve placed to connect two water pipes. The valve is a control system that will allow the flow of water through the pipes in one direction only.
This behavior reminds me with the valves in the human hart. Human heart has four valves that allow the flow of blood ONLY in one direction and never the opposite direction.
References:
http://www.st-andrews.ac.uk/~www_pa/Scots_Guide/info/comp/passive/diode/diode.htm
http://www.allaboutcircuits.com/vol_3/chpt_3/1.html
http://www.chipshow.com/blog/?cat=1
http://www.youtube.com/watch?v=JBtEckh3L9Q
http://www.youtube.com/watch?v=W6QUEq0nUH8
