This application relates to methods and apparatus for operating MEMS sensors, in particular MEMS capacitive sensors (CMEMS) such as a microphones. An amplifier apparatus (300) is arranged to amplify an input signal (VINP) received at a sense node (104) from the MEMS capacitive sensor. An antiphase signal generator (201; 304) generates a second signal (VINN) which is in antiphase with the input signal (VINP) and an amplifier arrangement (105; 305) is configured to receive the input signal (VINP) at a first input and the second signal (VINN) at a second input and to output corresponding amplified first and second output signals. This converts a single ended input signal effectively into a differential input signal.