A transistor “trans[formation res]istor” is an electronic part that amplifies electonic signals, power, and voltage through variable resistance.

In the early days of electronics it was found that a small voltage can control a larger voltage through a vacuum tube.
Transisters do the same job, but in a different way, and with alot less voltage. .

A diode is an electronic part that allows electricity to flow in one direction – its forward resistance is alot less than its reverse resistance.

A transistor can be thought of as a special kind of diode. Silicon,germanium,silicon chips are “doped” so that there are “holes” to which electrons can flow intoeasily, or can’t flow at all. By placing another, different substance in the middle, that third lead to the resistor can amplify, and strengthen signals.

Computer rooms used to be as big as houses, and its tubes had a quick burn out rate, so the machines had to be hard wired to do any work – work that a modern electonic calculator can do with ease. The transistor is cheaper, and alot smaller than tubes, and doesn’t use as nearly as much power, so 100′s of million of them can fit on a PC board instead of thousands of tubes.

Because of their quantum nature they are especially useful in logic circuits, addition circuits, and CPUs.

However, tubes aren’t dead quite yet – when a signal has to be greatly increased, as in a TV or radio transmitter, there’s a special tube – the klystron that does it alaot more effectively.

Transisters revolutionized electronics, making electronic devices cheaper and more reliable.