| 摘要 |
PURPOSE:To prevent the electrostatic breakdown of a gate oxide film, by a constitution wherein the gate length of an MOS transistor for driving the gate of an MOS transistor is made longer than the gate length of a driven MOS transistor, and the driven MOS transistor breaks down earlier than the MOS transistor for driving. CONSTITUTION:The gate length of each of MOS transistors 15 and 16 is made longer than the gate length of each of MOS transistors 3 and 4. Therefore the breakdown voltage of the MOS transistors 15 and 16 becomes high. When a switch 12 is turned ON, a switch 13 is turned ON earlier than a switch 17. Therefore, both voltages Va and Vb are decreased. Thereafter the value of the voltage difference Va-Vb does not become large. Since an excessive voltage is not applied to a capacitor 9, i.e., a part between the gates and the drains of the MOS transistors 3 and 4, the breakdown of the gate oxide film is prevented. |
