A high-voltage, low-leakage, bidirectional electrostatic discharge (ESD, or other electrical overstress) protection device includes a doped well disposed between the terminal regions and the substrate. The device includes an embedded diode for conducting current in one direction, and a transistor feedback circuit for conducting current in the other direction. Variations in the dimensions and doping of the doped well, as well as external passive reference via resistor connections, allow the circuit designer to flexibly adjust the operating characteristics of the device, such as trigger voltage and turn-on speed, to suit the required mixed-signal operating conditions.