In Plant Vehicle electronics, transistors are used for switching and amplification.

The switching action involves using the base/emitter circuit to switch on and off the collector/emitter circuit.

A second use of the transistor is amplification. It can take a very small input at the base/emitter and amplify it at the collector/emitter circuit. This larger signal can then be used to switch on and off 30 amp relays, or signal the ECU.

The amount by which the base/emitter signal is amplified is said to be the gain of the transistor. For example, the BC109 transistor commonly used on the course has a gain (hFE) of between 200 and 800, meaning that the collector/emitter current can be between 200 and 800 times greater than the base/emitter current.

Read more here about how to check the gain of a transitor

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