An on-chip circuit for protection against electrostatic discharge (ESD) is disclosed. Unlike conventional ESD protection circuit using high turn-on voltage diode string, the circuit uses a plural of enhancement-mode HEMT/MESFET triggered by a shorter diode string to shunt large ESD current for protected susceptive RF circuit. Further, by using dual-gate technology of enhancement-mode HEMT/MESFET, the on-chip ESD protection circuit has the less parasitic capacitance without expanding device size for vulnerable RF circuit.