Protective cct. for integrated MOS cct. - has control MOS transistor between cct. terminals and supply voltage source

The protection circuit is intended for an integrated MOS circuit on a semiconductor chip, as a safeguard against destruction owing to defective signals. Between the supply voltage for the semiconductor chip and the MOS circuit supply voltage terminals is incorporated a normally conductive, protective MOS transistor over its controlled path. The transistor constant is so chosen as to have a low resistance value in conductive state. The semiconductor chip is provided with a control voltage which applies a voltage to the control input of the protective transistor, when a combination of undesirable signals appear. This voltage converts the transistor into blocking state. Preferably the protective transistor is arranged on the semiconductor chip in a parallel configuration to the chip edge.