A transistor is a basic electrical component that alters the flow of electrical current. Transistors are the building blocks of integrated circuits, such as computer processors, or CPUs. Modern CPUs contain millions of individual transistors that are microscopic in size.
Most transistors include three connection points, or terminals, which can connect to other transistors or electrical components. By modifying the current between the first and second terminals, the current between the second and third terminals is changed. This allows a transistor to act as a switch, which can turn a signal on or off. Since computers operate in binary, and a transistor's "on" or "off" state can represent a 1 or 0, transistors are suitable for performing mathematical calculations. A series of transistors may also be used as a logic gate when performing logical operations.
Transistors in computer processors often turn signals on or off. However, transistors can also change the amount of current being sent. For example, an audio amplifier may contain a series of transistors that are used to increase the signal flow. The increased signal generates an amplified sound output. Because of their low cost and high reliability, transistors have mostly replaced vacuum tubes for sound amplification purposes.
While early transistors were large enough to hold in your hand, modern transistors are so small they cannot be seen with the naked eye. In fact, CPU transistors, such as those used in Intel's Ivy Bridge processor, are separated by a distance of 22 nanometers. Considering one nanometer is one millionth of a millimeter, that is pretty small. This microscopic size allows chip manufacturers to fit hundreds of millions of transistors into a single processor.