An electrostatic discharge (ESD) protection circuit for protecting one or more devices in an electronic circuit from an ESD current which enters the electronic circuit through one or more input/output pins, the protection circuit comprising: a voltage clamp circuit connectable to the or each pin, for diverting the ESD current from the or each device; and a current sensor circuit connected between the input/output pins and the voltage clamp circuit and connected to the one or more devices, the current sensor circuit for sensing the ESD current and for switching off the or each device when the sensed current exceeds a threshold value, wherein when a current flows in the current mirror circuits above a threshold value the device is caused to switch off.