SEMICONDUCTOR INPUT PROTECTIVE DEVICE

摘要

PURPOSE:To achieve the input protection of a substrate bias generating circuit without deteriorating the characteristics of the substrate bias generating circuit by connecting the input gate of a transistor to the output terminal of the substrate bias generating circuit. CONSTITUTION:The gate and source of an input protective transistor 20 are connected to the output terminal 7 of a substrate bias generating circuit and the drain of the transistor 20 is connected to a reference potential 6. When a potential much lower than a substrate bias potential is applied to the external terminal 7 of the substrate bias generating circuit, a current is applied by the breakdown characteristics mainly of an input protective transistor 21 or of the other input protective transistor 20 to protect the substrate bias generating circuit. When a potential higher than the reference voltage 6 is applied to the external terminal 7 of the substrate bias generating circuit, a current is applied by turning mainly the input protective transistor 20 or the other input protective transistor 21 ON the suppress the potential to the reference potential 6 or the potential of an electric source 8 to protect the substrate bias generating circuit.