PURPOSE: To obtain a semiconductor integrated circuit device with a protective circuit having high reliability on electrostatic breakdown by providing a MOSFET, which is brought to an OFF state by the supply of supply voltage and brought to a floating state by the interruption of supply voltage.
CONSTITUTION: A MOSFETQ1 and a MOSFETQ2 constitute an inverter circuit, and an output from the circuit is coupled with a gate for a MOSFETQ3 formed between an electrode P and the grounding potential point of the circuit. The gate for the MOSFETQ3 is brought to a floating state under the state in which a semiconductor integrated circuit device having such constitution is not supplied with supply voltage Vcc. Consequently, when static electricity Q is generated in the electrode P, high voltage is generated in the electrode P. The generated voltage V is transmitted over the gate under the floating state through a capacitor Cdg, and the MOSFETQ3 is brought to an ON state, thus instantaneously discharging said charges Q, then preventing the electrostatic breakdown of an input MOSFETQ4.
MUTO TADASHI
FUKUDA MINORU
FURUSAWA KAZUNORI
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