[ELI5] What is the need of Transistor configuration? Why do we need to consider a common terminal?

Question

[ELI5] What is the need of Transistor configuration? Why do we need to consider a common terminal?

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Answer 1

Transistors are valves that control the flow of current. This requires three wires, at least: 1) a source of current, 2) a common drain for current, and 3) a control wire to say how much current should flow.

If you just connect the source and control, you don’t have a complete circuit. The current could flow into the transistor but it would have no place to go. Electrons can’t “build up” in a device for very long, they repel each other.