The present disclosure relates to circuitry for selecting a bias voltage to output at a bias voltage output node of the circuitry. The circuitry comprises a first circuit node configured to receive a first voltage from a first, unregulated, voltage source and a second circuit node configured to receive a second voltage from a second, regulated, voltage source. A switch arrangement configured to selectively couple the bias voltage output node to the first circuit node or the second circuit node is also provided.