A power supply clamp connectable between power rails of an electronic circuit comprises a switching component which is switchable to provide a connection path between the power rails of the electronic circuit; a first detector configured to detect an electrostatic discharge event having a first characteristic time period and to generate a detector output signal in response to the detection; a series of one or more successive intermediate amplification stages between the first detector and the switching component, the series of amplification stages providing a control signal path for a control signal to control switching of the switching component in response to the detector output signal; and a second detector configured to detect an electrostatic discharge event having a second characteristic time period, shorter than the first characteristic time period, the second detector being provided at a node in the control signal path subsequent to the first detector (for example, at a second or subsequent one of the series of intermediate amplification stages) so that a detection by the second detector causes the control signal to control switching of the switching component.