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Transistors

Intrinsic semiconductors
The transistor consists of a thin central layer of one type of semiconductor between two relatively thick pieces of the other type. The junction transistor can be of two types pnp or npn. The pieces at either side are called the emitter and the collector while the central part is known as the base. The base is only about 3-5 mm thick.

Extrinsic semiconductors
These are semiconductors to which a very small amount of impurity has been added, this process is called doping. Doping with an impurity can have quite marked effects on the electrical properties of the material. The addition of one impurity atom in one hundred million will increase the conductivity of germanium by twelve times at 300 K.


 
 
 
© Keith Gibbs 2009