Question T6B03
From subelement T6 - T6B
Which of these components can be used as an electronic switch?
Why is this correct?
Transistors can function as electronic switches by using a control signal to turn current flow on or off between their other two terminals. A small control current (bipolar) or voltage (FET) switches a larger current, making them ideal digital switches. Varistors protect against voltage spikes, potentiometers adjust resistance values, and thermistors change resistance with temperature—none can actively switch current flow on command like transistors.
Memory tip
Think 'control signal = switching action.' Only transistors respond to an external control input to actively change their conduction state. The other components are passive—they react to conditions but don't actively switch circuits based on control signals.
Learn more
In amateur radio circuits, transistors enable digital modes, automatic antenna tuners, and T/R switching. They're fundamental to modern transceivers because they can rapidly switch between conducting and non-conducting states thousands of times per second. This switching capability enables everything from audio amplification to RF signal processing. Understanding transistor switching helps explain how your radio converts your voice into transmitted RF energy.
Think about it
Why do you think a transistor makes a better electronic switch than a mechanical relay for high-speed digital applications?