| 摘要 |
PROBLEM TO BE SOLVED: To increase electrostatic breakdown strength, and to lower an input bias current by clamping the voltage of an input terminal approximately at a first source voltage, when a voltage which exceeds the first source voltage and is lower than a voltage which turns a first protective diode on, is applied to the input terminal. SOLUTION: If a voltage higher than a first source voltage is applied to an input terminal t2, and the MOSFET M1 of a clamping means 24a is turned on, the voltage of the input terminal t2 is clamped at the sum voltage of a threshold voltage and the source voltage Vdd of the MOSFET M1. When an abnormal voltage is applied long and its voltage value is especially large, a first protective diode D1 is turned on, a current flows from the input terminal t2 to the source voltage Vdd, the voltage of the input terminal t2 is clamped at the sum voltage of the source voltage Vdd and a forward bias voltage of the protective diode, and breakdown of elements is prevented. Consequently, a high-reliability circuit which does not malfunction easily is obtained without lowering strength against electrostatic breakdown.
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