Transistors provide most of the activities a circuit needs to operate. In their most basic representation, transistors are amplifiers. That is, they take and amplify a signal from the level produced by a microphone and amplify it enough to blast it out through a speaker. Transistors are also used on decision making circuits, like electronic gates and Central Processing Units (CPUs). Solid state, electronic systems like desktop computers, cell phones, and GPS devices would not be possible without transistors.
