Patent ID: 7196889

Claim:
A plurality of overvoltage protection devices formed in a semiconductor substrate having a plurality of doped regions for forming semiconductor devices, the overvoltage protection devices adapted to draw current away from a device to be protected from excess voltage, each overvoltage protection device comprising: a switchable device having a terminal adapted to be coupled to a potential source of excess voltage and to the semiconductor substrate for drawing current away from the potential source of excess voltage when the switchable device being triggered and for directing the current to the semiconductor substrate; and a Zener diode coupled to a second terminal of the switchable device to trigger the switchable device to a conducting state; whereby current directed to the semiconductor substrate by a first overvoltage protection device causes the current to enter the semiconductor substrate wherein the switchable device of each circuit includes a silicon controlled rectifier, wherein the silicon controlled rectifier of each circuit includes an NPN transistor and a PNP transistor, the NPN transistor includes multiple emitters the NPN transistor being formed as a series of concentric rings around the base of the NPN transistor, wherein the semiconductor substrate includes a P-doped substrate overlaid by an N-epitaxial layer, and the Zener diode of each circuit being formed in a P-well in the N-epitaxial layer.