Overvoltage Protection with a CMOS-Compatible BJT

A new method of overvoltage protection in the supply path of CMOS circuits is described. The central device of the protection circuit is a CMOS-compatible npn bipolar transistor (BJT) which uses no n⁺ buried layer and can be manufactured in a simple p-well CMOS process without additional process steps. The device is especially suitable for high-voltage applications in electrically hostile environments such as automotive circuits.