TW282575B - Electrostatic discharge protection circuit - Google Patents

Abstract

A protection circuit of semiconductor chip operating circuit(11), in which the semiconductor chip is connected to one pad(9) on which there could appear electrostatic discharge voltage, comprises of: one field oxide field effect transistor(15) whose drain is connected with the pad, and source(14) is grounded, and which could clamp pad voltage on powering on field oxide transistor; one trigger field transistor(20) whose source(19) is grounded and drain(22) is coupled with the field oxide field effect transistor(15) so as to receive pad electrostatic discharge voltage, in which the trigger field effect transistor will happen avalanche under electrostatic discharge voltage, and gate oxide of trigger field effect transistor will happen oxide breakdown under electrostatic discharge voltage, even burn down by heat when the oxide breakdown current is very high; one resistor(31) connected between gate of trigger field effect transistor and ground, making trigger transistor maintain close when signal voltage enters pad, and opening trigger field effect transistor by oxide and avalanche when electrostatic discharge voltage enters pad so as to generate one electron pair; allocation position of the trigger field effect transistor and field oxide field effect transistor could make charge generated from trigger field effect transistor avalanche enter and power on field oxide transistor to clamp electrostatic discharge voltage; the resistance is high enough to protect trigger field effect transistor from damage before powering on the field oxide field effect transistor, therefore preventing operating circuit or trigger field effect transistor from damage.