This is a transistor video tutorial. This video describes about transistor and how it works. Transistor can be used as amplifier or switch. There are many kinds of transistor, in this video  bi-polar transistor is described. There are two kinds of bi-polar transistor, NPN and PNP. Bi-polar transistor has three layer, they are input layer, control layer and output layer. Bi-polar transistor contains emitter, base, and collector. Here is the video :