An overvoltage protection device protects an electronic medical device in the event of a transient overvoltage on one or more patient lines of the device. A current limiting device is placed in series in a patient line between electronic components of the medical device and a patient interface. A biasing voltage generating device has at least one biasing element located in a line extending off the patient line and at least one additional circuit element connected in series with the biasing element. The biasing voltage generating device is configured to apply a predetermined biasing voltage to the current limiting device via the biasing element in response to a transient overvoltage on the patient line, whereby the current limiting device is switched off and limits current flow through the patient line.