Patent ID: 8633509

Claim:
An apparatus comprising: an internal circuit electrically connected between a first node and a second node; and a protection circuit electrically connected between the first node and the second node, wherein the protection circuit is configured to protect the internal circuit from transient electrical events, the protection circuit comprising: a bi-directional bipolar device having an emitter/collector, a base, and a collector/emitter, wherein the base of the bi-directional bipolar device is electrically coupled to a buried layer having a doping of a first type; a first bipolar transistor having an emitter electrically coupled to the first node, a base electrically coupled to the emitter/collector of the bi\-directional bipolar device, and a collector electrically coupled to the base of the bi-directional bipolar device through the buried layer; and a second bipolar transistor having an emitter electrically coupled to the second node, a base electrically coupled to the collector/emitter of the bi\-directional bipolar device, and a collector electrically coupled to the base of the bi-directional bipolar device through the buried layer; wherein the base of the bi-directional bipolar device is electrically coupled to a first central well having a doping of the first type, wherein the base of the first bipolar transistor is electrically coupled to a first well having a doping of a second type opposite the first type, wherein the base of the second bipolar transistor is, electrically coupled to a second well having a doping of the second type, and wherein the first central well is positioned between the first and second wells; wherein the first well comprises a first active region and a second active region, the second active region having a portion farther from the first central well than at least a portion of the first active region, the first active region having a doping of the first type, the second active region having a doping of the second type, wherein the first active region is electrically coupled to the base of the first bipolar transistor, wherein the second active region is electrically coupled to the emitter of the first bipolar transistor, and wherein the second well comprises a third active region and a fourth active region, the fourth active region having a portion farther from the first central well than at least a portion of the third active region, the third active region having a doping of the first type, the fourth active region having a doping of the second type, wherein the third active region is electrically coupled to the base of the second bipolar transistor, wherein the fourth active region is electrically coupled to the emitter of the second bipolar transistor.