CIRCUIT FOR PROTECTING STATIC ELECTRICITY

摘要

PURPOSE: A circuit for protecting static electricity is provided to improve the reliability and the yield rate of a device by preventing static electricity and accomplishing CDM protecting characteristics. CONSTITUTION: A first NPN bipolar device disperse the static electricity applied to a pad end and outputs the static electricity to an applying end of a power source voltage. A second NP:N bipolar device disperse the static electricity applied to the pad end and outputs the static electricity to an applying end of a ground voltage. A resistor is connected between the pad end and a gate end of a CMOS circuit, and maintains the turn on time of the second NPN bipolar device. A NMOS transistor is connected between the gate end of the CMOS circuit and the applying end of the power source voltage. The NMOS transistor is turned on to accomplish the clamping operation when the voltage of the input end is increased up to over a predetermined level.