Circuit and method of reverse voltage protection using a lateral transistor having a collector ring surrounding its base region

摘要

A lateral transistor (14) is configured as a reverse protection diode that allows low and high current modes of operation while maintaining low forward voltage drop. The base region (38) of the lateral transistor is formed inside a collector ring (34) and adjacent to the emitter region (36). In low current mode, the transistor operates as a conventional diode. In high current mode, the excessive number of minority carriers injected into the base region causes the device to enter conductivity modulation that effectively increases the doping concentration and lowers the bulk resistance. The lower bulk resistance keeps the forward voltage drop low. By having the base region inside the collector ring, the bulk resistance is kept low to aid in the onset of conductivity modulation. Thus, the transition between low current mode and high current mode is minimized.