Transistors are electronic components that have the ability to change materials can conduct electricity to the conductor or semi-conductor material which is also called a semiconductor material.
Transistor is actually a result of the development of two types of PN and NP diodes are brought together so as to form an electrode that serves as the controller between material meeting the PN and NP. The principle of the second meeting of the material can be illustrated in the following figure,
As shown in the figure above, when the two materials were brought his P-type material, it will obtain the NPN transistors.
Also seen in the picture above, if the two materials N-type material reunited her, it will form a PNP transistor type.
The results of the both meeting substance P and N transistors will produce components which feature 3 feet is the emitter (E), base (B), collector (C). Based on these principles, it is called transistor Bipolar transistor PNP and NPN types.
The difference between NPN and PNP transistors are located on the arrow at the foot emitornya (E). In the NPN transistor arrows mark heading out while the PNP transistors arrows mark heading into.