一种0.8V衬底驱动轨对轨运算放大器设计

采用衬底驱动技术设计低压低功耗轨对轨运算放大器。输入级采用衬底驱动MOSFET,有效避开阈值电压限制,将电源电压降至0.8V,实现低压下轨对轨共模输入范围。增加衬底驱动冗余差分对及反折式共源共栅求和电路实现恒定跨导控制,消除共模电压对输入级跨导的影响,输出采用前馈式AB类输出级,以提高动态输出电压范围。基于标准0.18μmCMOS工艺仿真运放,测得输出范围0.4～782.5mV,功耗48.8μW,电源抑制比58dB,CMRR65dB,直流开环增益63.8dB,单位增益带宽2.4MHz,相位裕度68°。版图设计采用双阱交叉空铅技术,面积为97.8μm×127.6μm。

A 0.8 V Bulk-driven Rail-to-Rail Operational Amplifier

A low-voltage low-power rail-to-rail amplifier is introduced based on the bulk-driven technique.Bulk-driven MOSFETs at the inputs avoid the limitation of threshold voltage efficiently so as to reduce the power supply to 0.8 V,and achieve rail-to-rail common mode input voltage operation in extremely low-voltage environments.Bulk-driven redundant differential pairs and reversed folded cascade summing keep the total transconductance constant to eliminate the effect on input transconductance caused by common mode voltage.The output stage is employed as feed-forward class-AB to enhance output dynamic range.Based on the standard 0.18 μm CMOS process the amplifier is simulated.The simulated out swing is 0.4～782.5 mV,power dissipation is 48.8 μW,PSRR is 58 dB,CMRR is 65 dB,DC gain of the amplifier is 63.8 dB,unity-gain frequency is 2.4 MHz,and phase margin is 68°.Dual-well cross-quading technique is introduced in the layout for matched devices and the area of the layout is 97.8 μm×127.6 μm.