WORKING OF GENERAL TRANSISTORS NPN & PNP

We all know about the transistors they have most important role in electronic field. Here am going to explain about how the transistor work , both PNP and NPN. Mostly the transistors used as switches in electronic circuits.

 NPN means two N layers are sandwitched between one P layer. N region are rich in  with free electrons . And P region have holes and less number of free electrons. P region is the base in NPN transistors. When NPN  transistor in free state they don't have connection with collector and emitter because of the P region between it.
When we apply a +Vcc in to the base region, the depletion layer became thinner and break then the collector and emtiter are become internally connected and the circuit became close. If there is any voltage in the collector it will come to emitter also. So we can controlled the NPN transistor by applying varies voltage. When no voltage in base it in open and when +Vcc is given it became ON .

In case of PNP transistor the base is N region it contain more electrons . But emitter and collector has more holes. When the emitter is connected with +Vcc and the collector is ground position and in base has only small voltage input the electrons get it became thin and then naturally emitter and collector are internally contact each other. Because the base depletion became more thin. When base is have high voltage the depletion layer is in high size. So the emitter and collect not contact each other. So the the transistor is in off state.

Thus the transistor can used as perfect switch. Due to this property transistor are used in more electronic circuits. Use this property we can make simple electronic circuits.