Which device is used to amplify or switch electronic signals?

The transistor is a semiconductor device that plays a crucial role in modern electronics by amplifying or switching electronic signals. Its ability to control the flow of electrical current makes it an essential component in various electronic circuits and devices. Transistors can take a small input signal and produce a larger output signal, which is fundamental to functions such as signal amplification in radios or controlling the flow of current in digital computing applications.

In addition to their amplifying capabilities, transistors are also integral to switching applications in digital circuits. They can be turned on or off by applying a voltage to the gate, acting as an electronic switch that enables or disables the flow of current. This property is utilized in everything from microprocessors to digital logic circuits, enhancing processing speed and efficiency.

Transistors have largely replaced earlier technology such as vacuum tubes and even certain uses of integrated circuits for many applications due to their smaller size, lower power consumption, and greater reliability. While integrated circuits can contain multiple transistors, the specific function of amplifying or switching is primarily attributed to the operation of transistors themselves. Thus, the correct choice highlights the fundamental role of transistors in electronics technology.