Semiconductor input protection circuit

摘要

A lateral PNP transistor PB and a lateral NPN transistor NB are serially connected between an input terminal and a reference potential (ground potential). In the transistor PB, a diode D₁ is formed. In the transistor NB, a diode D₃ is formed. When an ESD of +2000 V is input, the transistor NB turns on, whereas when an ESD of -2000 V is input, the transistor PB turns on. The level of a positive signal capable of being input is limited by the inverse breakdown voltage (e.g., 18 to 50 V) of the diode D₃, whereas the level of a negative signal capable of being input is limited by the inverse breakdown voltage (e.g., 13 to 15 V) of the diode D₁.