PROTECTIVE DEVICE FOR SEMICONDUCTOR INTEGRATED CIRCUIT

PURPOSE:To enhance the breakdown resisting strength without increasing the measurements of an internal circuit element by a method wherein an NPN transistor, on which a base is open-circuited between the power supply of the integrated circuit and the ground, is added. CONSTITUTION:An integrated circuit consisting of a transistor 5 and the like, is formed on a p type semiconductor substrate 20. A diode 9 is composed of the n type region 23 of the transistor 5, a buried layer 21 and a substrate 20, and a resistor 8 and a transistor 11 are formed in the other island region 24 located on the substrate 20. The collector 32 of the transistor 11 and one end of the resistor 8 are connected to the power source, and the other end of the resistor 8 is connected to the n collector region 30 of the transistor 5. A diode 10 consists of the resistor 8, a region 24 and an n layer 31. When the NPN transistor 11, whereon the base is open-circuited, is added in-between the power source and the ground, the sections between the input terminal and the power source, and the output terminal and the power source are clamped at a constant voltage, and the withstand voltage breakdown of the integrated circuit can be prevented.