ARRL Technician Practice Exam

Which of these components can be used as an electronic switch or amplifier?

1. Diode

2. Resistor

3. Transistor

4. Capacitor

The correct answer is: Transistor

A transistor is a crucial component in electronics that can function both as an electronic switch and as an amplifier. When used as a switch, it can control the flow of current in a circuit, toggling between on and off states based on an input signal. This capability makes transistors fundamental in digital circuits, where they perform tasks akin to traditional mechanical switches, enabling complex operations like logic processing. As an amplifier, a transistor can take a small input signal and produce a larger output signal. This feature is essential in audio devices, radio transmission, and many other applications where signal amplification is necessary. The transistor achieves this through its three-terminal structure (the collector, base, and emitter), allowing a small current at the base terminal to control a larger current flowing from the collector to the emitter. In contrast, other components mentioned, such as diodes, resistors, and capacitors, serve specific functions; diodes allow current to flow in one direction but cannot amplify or switch in the same versatile manner as transistors. Resistors limit current flow and do not have switching or amplification capabilities, while capacitors store and release electrical energy but do not control the flow of current like a switch or effectively amplify signals.