Patent ID: 7619401

Claim:
A bandgap circuit, comprising: a first amplifier; a second amplifier; a reference circuit, being electrically connected to an output terminal of the first amplifier and including: a first metal oxide semiconductor having a gate, a source, and a drain, the first metal oxide semiconductor connected to the output terminal of the first amplifier, a second metal oxide semiconductor having a gate, a source, and a drain, the second metal oxide semiconductor connected to the output terminal of the first amplifier, and the drain of the second metal oxide semiconductor electrically connected to a first resistor for correcting the voltage of the drain of the second metal oxide semiconductor, a third metal oxide semiconductor having a gate, a source, and a drain, the third metal oxide semiconductor connected to the output terminal of the first amplifier, a first bipolar junction transistor having a base, a collector, and an emitter, the first bipolar junction transistor electrically connected to the drain of the first metal oxide semiconductor, and a second bipolar junction transistor having a base, a collector, and an emitter, said second bipolar junction transistor electrically connected to the drain of the second metal oxide semiconductor via the first resistor, wherein the current through the first resistor is a proportional-to-absolute-temperature (PTAT) current that is proportional to the natural logarithm of N/R, where N is the ratio between the area of the emitter associated with the first bipolar junction transistor and the area of the emitter associated with the second bipolar junction transistor, and where R is the resistance of the first resistor, and wherein the source of each of the metal oxide semiconductors is jointly and electrically connected to a power supply and each of the metal oxide semiconductors providing equal drain currents; and a compensation circuit, electrically connected to the power supply to which each of the metal oxide semiconductors is electrically connected, and including a plurality of transistors and the second amplifier, wherein the gates of the plurality of transistors are jointly connected to the output terminal of the second amplifier, and wherein the first amplifier provides an input to the second amplifier, whereby the reference circuit outputs a stable startup voltage that has a low sensitivity to a change of temperature and a change of supplied voltage.