PROTECTIVE CIRCUIT AGAINST ELECTROSTATIC DISCHARGE DAMAGE

摘要

PROBLEM TO BE SOLVED: To provide a protective circuit against electrostatic discharge damage with improved performance (operating speed and resistance to electrostatic discharge damage) for protecting an internal circuit against surge voltage such as static electricity. SOLUTION: An n-channel MOS transistor 5 is connected between a wire 3 and a VSS (ground voltage) wire 4. A first capacitor 6 is connected between the wire 3 and the gate of the MOS transistor 5, and a second capacitor 7 is connected between the VSS wire 4 and the gate. A voltage applied to an input/output terminal 2 is divided by these capacitance elements, and a corresponding divided voltage is applied to the gate. When a surge occurs, the MOS transistor 5 is forced to be turned ON by the divided voltage to make current flow, thereby protecting the internal circuit 1. A parasitic bipolar transistor is turned ON against a further excessive surge. A Zener diode 8 is provided between the gate and the VSS wire 4 to prevent the voltage applied to the gate from rising to a predetermined or higher voltage. COPYRIGHT: (C)2008,JPO&INPIT