What is the best explanation for how a differential amplifier functions?

A differential amplifier is designed specifically to amplify the difference in voltage between two input signals while rejecting any noise or signals that are common to both inputs. This characteristic makes it particularly useful in applications where accurate signal measurement is required despite the presence of potentially disruptive interference.

The essential function of a differential amplifier lies in its ability to take two input voltages and produce an output that is proportional only to the voltage difference between them. This is crucial for maintaining the integrity of the signal, particularly in the context of medical monitoring technologies where precise readings are necessary, such as in polysomnography.

The other options describe functions that do not accurately capture the primary role of a differential amplifier. For instance, while eliminating noise is a beneficial side effect of using a differential amplifier, it is not its main function; rather, its design inherently provides noise rejection. Similarly, while a differential amplifier can be part of systems that process signals, it does not inherently convert analog signals to digital; that function is typically associated with other components like analog-to-digital converters. Lastly, the idea that it creates a single output from multiple inputs mischaracterizes the amplifier's purpose since its output specifically represents the difference between two inputs, rather than averaging or combining them into a single output.