An apparatus (100) for protecting a circuit (200) from an input volume comprises a switchable element (10) arranged to couple the input voltage (VIN) to the circuit (200) in response to a first control signal (DRV1) having a first value and to decouple the input voltage (VIN) from the circuit (200) in response to the first control signal (DRV1) having a second value. A monitor stage (20) compares a monitored voltage (VMON) to a threshold (VIN). A controller (30) provides the first control signal (DRV1) to the switchable element (10), the first control signal (DRV1) having the first value when the monitored voltage (VMON) is on one side of the threshold (VTH) and the second value when the monitored voltage (VMON) is on the other side of the threshold (VTH), wherein the first value is independent of the input voltage (VIN) and the second value is equal to the input voltage (VIN).