Transistor

It switches a large voltage with a smaller one.

A good analogy which applies to FETs (field effect transistors) is to imagine a soft hosepipe with water flowing through it, by applying a small variation in pressure to pinch the pipe you can control a big flow of water.
Del

Do also check out the Wikipedia pages on this topic.

I was once told it was because of magic smoke, that is why when the magic smoke leaks out of the transistor it stops working.

I always thought a transister was a brother who had an operation and became a sister.

I learn something new every day in here...

A transistor has three leads, two of which can carry a lot of current, and a third leg which I call the "signal lead". The other two leads have an inlet side (which never changes voltage) and an outlet side whose voltage goes up and down according to what the signal lead tells it to do.

A small change of voltage on the signal lead of the transistor will cause a greater or lesser resistance to be created between the other two leads. That changing resistance will result in a changing voltage drop at the outlet. The amount of voltage drop will vary directly with the applied voltage to the signal lead. That big voltage drop which exactly mirrors the tiny applied voltage is what we call "amplification".
You can never get a higher voltage at the output of the transistor than what you apply to the inlet side.

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This was an exercise on my part. It has been years. Anybody think it was too simplified?