Correcting for non-linearity in an amplifier providing a differential output

A differential amplifier to amplify an input signal received across a pair of signal input terminals, and to generate an amplified signal across a pair of output terminals, wherein a common-mode voltage is present on each of said pair of output terminals, said amplifier comprising:

• a first gain block having a pair of input nodes, the output of said first gain block being provided across said pair of output terminals;
• a first feedback resistance between a first input node of said pair of input nodes and a first output terminal of said pair of output terminals;
• a second feedback resistance between a second input node of said pair of input nodes and a second output terminal of said pair of output terminals;
• a first input resistance between said first input node and a first one of said pair of signal input terminals;
• a second input resistance between said input node and a second one of said pair of signal input terminals;
• a common-mode voltage generator block to generate a common-mode voltage, wherein said common mode voltage is applied to each terminal of said pair of output terminals, wherein during a normal operation of said differential amplifier, said common-mode voltage is designed to be a varying voltage;
• and
• a calibration unit comprising a pair of reference resistances, said calibration unit operable to:
• equalize a first ratio of said first feedback resistance to said first input resistance with that of a reference ratio of said pair of reference resistances;
• and
• equalize a second ratio of said second feedback resistance to said second input resistance with that of said reference ratio,
• wherein maintaining said first ratio equal to said second ratio prevents variations in said common mode voltage from contributing an erroneous differential signal component across said pair of differential output terminals.