Which device is commonly used to amplify signals?

• A. Resistor
• B. Capacitor
• C. Transistor
• D. Diode

Answer: (C)

Amplification comes from an active component that can control a larger output with a smaller input. The transistor does exactly that: a small current or voltage at its input modulates a much larger current between its other terminals, providing gain. This makes it the fundamental building block for amplifiers in analog circuits, like boosting a weak microphone signal into something strong enough to drive a speaker.

Resistors are passive components that simply dissipate or set levels; they don’t amplify. Capacitors store and release energy, enabling coupling, timing, or filtering, but they don’t increase signal strength. Diodes conduct in one direction and are used for rectification or switching, not to provide linear gain.