Which instrument amplifies the common-mode voltage difference between two inputs?

A differential amplifier is designed specifically to amplify the voltage difference between two input signals while rejecting any signals that are common to both inputs, known as common-mode signals. This ability makes differential amplifiers essential in various applications, especially where noise cancellation is necessary, as they can enhance the signal of interest while minimizing interference from external noise or unwanted signals that affect both inputs equally.

In contrast, an impedance meter measures resistance, capacitance, or inductance without amplifying signals. An A/D (analog-to-digital) converter is responsible for converting analog signals into digital format, but it does not amplify voltages. The Fast Fourier Transform (FFT) is an algorithm used for transforming signals from their original domain to a representation in the frequency domain; it does not amplify or process common-mode voltages. Thus, the differential amplifier is uniquely suited for amplifying the difference in signals while suppressing noise, solidifying its role in instrumentation where precise measurements are required.