ESD protection device with FET circuit

摘要

An FET is connected between ground and a pad to be protected from an ESD voltage, and when an ESD voltage appears at the pad the drain-channel junction breaks down and produces hole-electron pairs that turn on a parasitic bipolar transistor which clamps the voltage at the pad. A resistor connects the gate of the FET to ground. As the ESD voltage rises at the pad, the gate to drain capacitance charges in circuit with the resistor. The voltage across the gate oxide rises slowly enough that the FET is enabled to produce hole-electron pairs for turning on the bipolar transistor before the oxide voltage has reached a value that might damage the gate oxide.