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Transistor, Meaning (SPM Physics)

A semiconductor device with three terminals used to amplify signals or to act as an electronic switch.

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Definition

A semiconductor device with three terminals used to amplify signals or to act as an electronic switch.

Electronics

In exam terms

A transistor is a semiconductor device with three terminals used to amplify signals or to act as an electronic switch. In a common junction transistor the three terminals are the base, collector and emitter; a small current into the base controls a much larger current through the collector and emitter.

Example of correct use: in a switching circuit, when the base current is large enough the transistor turns on and lets current flow through the collector, so a small input can switch on a lamp.

Do not confuse it with…

Do not confuse a transistor with a diode. A diode has two terminals and only lets current pass one way; a transistor has three terminals and uses a small base current to control a larger current, so it can amplify or switch.

In Paper 2 you may be asked to state the two uses of a transistor or to explain how it works as a switch; name the base, collector and emitter and describe the base current controlling the main current.

Source: DSKP KSSM Physics Form 4 and 5 (Versi English) (Bahagian Pembangunan Kurikulum (BPK), KPM)

Frequently asked questions

What are the two main uses of a transistor?
To amplify signals and to act as an electronic switch.
What are the three terminals of a junction transistor?
The base, the collector and the emitter.
How does a transistor act as a switch?
A small base current turns the transistor on, allowing a much larger current to flow through the collector and emitter; without enough base current it stays off.

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