A circuit for protecting against electrostatic discharge events has a semiconductor substrate (200) of first conductivity embedding a first diode in a well (260) of opposite second conductivity, the diode's anode (111) tied to an I/O pin-to-be-protected (101) at a first voltage, and the first diode's cathode (112) connected to the first drain (123) of a first MOS transistor in the substrate. The first MOS transistor's first gate (122) is biased to a second voltage smaller than the first voltage, thereby reducing the first voltage by the amount of the second voltage. In series with the first MOS transistor is a second MOS transistor with its second drain (670) merged with the first source of the first MOS transistor, and its second source (131), together with its second gate (132), tied to ground potential (140).