Designers of low-distortion analog circuits in industrial data acquisition, seismic measurement, and high-fidelity audio are aware that many operational amplifiers (op amps) produce greater distortion when configured as non-inverting amplifiers. In the non-inverting configuration, the input signal appears as a common-mode signal at both inputs. The subtraction performed by the op amp on the two inputs is finite and slightly non-linear, producing a small amount of additional distortion at the op amp output. This effect is often referred to as common-mode distortion.