Circuit protection

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