Which of the following describes the function of a differential amplifier?

The function of a differential amplifier is accurately described by the notion of capturing the differences in the voltages of two inputs. This is crucial because a differential amplifier is specifically designed to amplify the difference between its two input signals while rejecting any common noise or interference that may be present on both inputs.

In many applications, especially in the context of medical devices like electromyography (EMG) or electrocardiography (ECG), this capability allows for more accurate readings, as the noise typically affects both inputs similarly. Therefore, by focusing solely on the voltage difference, the differential amplifier provides a clear signal that reflects the true electrical activity being measured, free from external noise and disturbances.

The other options present variations of input voltage concepts but do not capture the full scope of what differentiates a true differential amplifier. They may represent aspects of amplifying signals but do not address the foundational aspect of measuring the voltage difference between two inputs, which is fundamental to the operation and purpose of the differential amplifier in various electronic and medical applications.