Overvoltage protection circuit

摘要

The provision of an overvoltage protection circuit that can be structured with a small number of elements in the same semiconductor substrate along with a CMOS integrated circuit to be protected. An overvoltage protection circuit 1 comprising a voltage divider 2 comprising a first resistance element 21 and a second resistance element 22, which divide the voltage that is supplied from an external power supply terminal 11, an inverter circuit 3 comprising a third resistance element 32, and a high voltage MOS transistor 31 which uses as its input the voltage of the voltage division point of this voltage divider circuit 2, and a switching element 4 comprising a high voltage MOS transistor 41 that cuts off excessive voltage supplied to the CMOS integrated circuit 5 to be protected, is fabricated in the same semiconductor substrate as the CMOS integrated circuit 5.