A data buffer comprises data storage circuitry; input circuitry to input data to be stored by the data storage circuitry at a first operating voltage; output circuitry to output stored data from the data storage circuitry at a second operating voltage different to the first operating voltage; and control circuitry to control an operating voltage of the data storage circuitry to be substantially the first operating voltage during a data input operation by the input circuitry and to be substantially the second operating voltage during a data output operation by the output circuitry.