What aspect of a signal does a differential amplifier primarily measure?

A differential amplifier primarily measures the voltage difference between two inputs. This type of amplifier is designed to amplify the voltage difference while rejecting any voltage common to both inputs, which is known as common-mode voltage. This characteristic makes differential amplifiers particularly useful in applications where noise reduction is important, as they can effectively eliminate interference that may be present equally on both inputs, thus enhancing the accuracy of the measurement.

The fundamental operation involves taking the difference between the two input signals and amplifying this value. Therefore, when analyzing signals in various electronic systems, understanding this voltage difference is crucial for accurate signal processing. In contexts where precise measurements of varying signals are necessary, such as in medical instrumentation or data acquisition systems, the differential amplifier's ability to focus solely on the difference between two signals is invaluable. Other options, such as frequency content, phase difference, and power level, do not fundamentally pertain to the primary function of a differential amplifier, which is to amplify the voltage difference.