Abstract: The gate insulator of an IGFET, whose gate is connected to the input terminal of a circuit, is protected by limiting the potential difference between any two circuit terminals. Each input and output terminal of the circuit is connected via protective diodes to the power supply lines of the circuit and a high conductivity, low reverse dynamic impedance, diode is connected between the power supply lines. The reverse voltage across the high conductivity diode is less than that of any other diodes at a given current level, whereby only the high conductivity diode conducts substantial currents in the reverse direction.

Abstract: A protection circuit for a monolithic integrated circuit in which regions of one conductivity type are formed in a common substrate of complementary conductivity type and in which a first voltage is applied to the substrate to prevent forward conduction through the junctions formed between the regions and the substrate. The protection network includes a control element, responsive to the first voltage, which is connected between a second voltage point and selected regions for coupling the voltage at the second point to the selected regions only in response to the presence of the first voltage. This prevents the junctions formed by the selected regions and the substrate from being forward biased and carrying excessive and/or destructive currents when the first voltage is absent.