INPUT/OUTPUT BUFFER CIRCUIT

PURPOSE:To offer an input/output buffer circuit provided with a high voltage output function and an input function with extremely simple constitution, by using a gate ground type amplifying MOSFET of high voltage resistance, connecting its source and a substrate connected in common, to an input/output terminal side of a semiconductor integrated circuit, and using its drain side as an input/output terminal to other circuit device. CONSTITUTION:In case when a semiconductor integrated circuit device LSI is operated by a positive power supply voltage Vcc (for instance, +5V), a P channel MOSFET of high voltage resistance is used, and the gate of these MOSFETs Q3, Q4 is connected steadily to a ground potential point of the circuit, by which a gate ground type amplifying circuit is constituted. The source of these MOSFETs Q3, Q4 and a substrate (channel) are formed in common and connected to terminals P1, P2 of said semiconductor integrated circuit device LSI. Also, the drain side of these MOSFETs Q3, Q4 is connected to input/output terminals P3, P4 to other circuit device.