Transistors are made of the same silicon material that is used to create diodes, however they are slightly more complex internally. Most transistors are constructed in layers, with a piece of "P" material sandwiched between two other pieces of "N" material. (P and N refer to Positive and Negative.) The polarity of the silicon material is determined when it is manufactured, and this is something you'll just have to take for granted right now. By the way, some transistors are made in the reverse -- two pieces of P surrounding a single N. But that's really not important. What is important, however, is the properties these materials possess.

    Earlier in this discussion we used analogies to show how the flow of electricity is very much like the flow of water. And that's true. Though it was alluded to then, we didn't quite get around to comparing a water faucet with its electronic counterpart, which is a transistor. In fact, the British still refer to a vacuum tube -- the transistor's predecessor -- as a valve. Just as a 98 pound weakling can control hundreds of pounds of water pressure by merely turning a valve (well okay, a big valve), a transistor can likewise be coaxed into controlling a large amount of current by applying a smaller one to it.

    Most transistors have three connecting wires, and the current to be controlled is attached to two of them. The third wire is used for a control voltage, and it can regulate the amount of electricity that flows between the other two. This is a very powerful concept, since a small amount of current can be used to control a much larger one, which results in amplification. By the way, the ratio of the amount of controlling current that is required versus the amount being controlled is called a transistor's gain.

    Armed with all of this knowledge, it's not very hard to see how a stereo phonograph works. A playback needle is attached to a tiny magnet, which is placed near a coil of wire that creates a voltage when the magnet moves. The coil is then attached to a transistor that controls the power from the power supply, which is connected to a speaker. And the knee bone's connected to the thigh bone, and the...

    The more the phonograph needle wiggles, the more the loudspeaker at the end of the chain moves. And the faster the needle travels, then the faster the speaker moves. Simple, right? Right!