Low voltage band gap circuit and method

摘要

A band gap circuit that may be implemented in a standard CMOS process including a pair of parasitic vertical PNP transistors operating at a different current density. The PNP transistors have common collectors and common bases and produce a difference in base-emitter voltages which is developed across a resistor so as to produce a current having a positive temperature coefficient. The current is used to produce a positive temperature coefficient voltage which is combined with another voltage having a negative temperature coefficient to produce a band gap reference voltage. A bias voltage is applied between the base and collector of each of the PNP transistors, typically on the order of 500 millivolts. This causes the emitters of the PNP transistors to be at a voltage which can be sensed by an error amplifier implemented with standard N type MOS input transistors while maintaining a capability of operating using a relatively low power supply voltage.