Design Of CMOS Bandgap Reference With High Precision And High PSRR

The voltage reference, which has been widely used in analog，mixed-mode anddigital circuits, is a necessarily cell in IC. As the feature size of integrated circuitsgetting smaller in recent years, power supply voltage and power consumption of thechip is getting lower and lower, and higher performances are required for referencesources. Accuracy, thermal stability and PSRR (Power Supply Rejection Ratio) of thevoltage reference circuit will influence the precision and performance of the wholesystem.The bandgap reference has advantage in power supply, power consumption andstability, which makes it to be used most popular. In this thesis a CMOS bandgapreference is designed with high accuracy and PSRR. Firstly, the performance index,basic theory and structure is introduced with emphasis on high-order temperaturecompensation methods. The paper utilizes the current-mode structure to achieve theworking under low power supply. The VBElinearization compensation method is usedto carry out higher-order temperature compensation. In order to improve the PSRR ofbandgap reference, a voltage subtractor circuit is inserted into the conventionalbandgap reference. The subtractor introduces the supply noise directly into thefeedback loop of the bandgap circuit which could help to suppress supply noise.Based on SMIC0.18μmCMOS process, the bandgap reference is simulated byCadence spectre. The gain of op-amp can reach to89.8dB. The temperature coefficientis2.467ppm/℃in the temperature range-40～125℃. PSRR at low frequency is-113dB, which has a34dB improvement compared to conventional bandgap reference.