What characteristic distinguishes an analog circuit from a digital circuit?

An analog circuit is distinguished by its operation on continuous signals, meaning it can represent a range of values with variable voltage levels. The characteristic of having variable voltage values allows analog circuits to replicate real-world phenomena accurately. This ability to handle an infinite number of states, rather than just a finite set of discrete levels, defines the essence of analog functionality.

The signal in an analog circuit can change fluidly and represent any voltage level within a specified range, such as the varying sound levels in an audio signal or temperature variations in a sensor. This contrasts with digital circuits, which operate using discrete signals and represent information in binary form, where values are limited to distinctly defined levels.

Understanding this fundamental difference in signal representation helps clarify the capabilities and applications of both analog and digital circuits in electronic design.