| 摘要 |
PURPOSE: To prevent an excessive voltage from being applied to a gate electrode, by forming a protective element between the gate terminal of a MOSFET and a power supply terminal or the source terminal which MOSFET constitutes an internal logic circuit having different power supply system. CONSTITUTION: Between the gates and the sources of MOSFETs Q21, Q22 which constitute an inverter circuit G2, MOSFETs Q23, Q24 for leakage use are connected as protective elements. The M0SFETs Q23, Q24 are diode- connected wherein the gates are coupled to the sources. When an electrostatic pulse P is applied to a power supply terminal T1 or T2, and electrostatic noise like P1 appears on a power supply line L1, a leak current flows in the MOSFET Q23, decreasing the potential difference between the gate and the source of the MOSFET Q21. Thereby an excessive voltage is prevented from being applied across the gate and the drain or across the gate and the drain of an MOSFET, and breakdown of a gate insulating film can be avoided. |
