Abstract: The principle of the influence on the offset caused by MOSFET mismatch is analysed. The mechanism of the chopped modulator technology to decrease the offset and increase the accuracy of a BGR is introduced. A design of a low voltage bandgap reference (BGR) is implemented by considering these mechanisms and the chip layout is presented. To compensate the error caused by the offset of an opamp, the chopper modulator is used in the BGR circuit. Considering that the mismatch of current-mirror and differential input pairs is ±2%, the peak-to-peak value of the output ripple is 0.31mV. The relative accuracy is increased by 86 times compared with the BGR without chopped modulators. The temperature coefficient is about 12×10^-6/℃ at temperature range from 0℃ to 80℃. The area of the layout is 0.3mm×0.4mm with a standard 0.25μm 2P5M CMOS process.

Key words: offset voltage, chopped modulator, bandgap voltage reference