双斜率积分ADC中开关电容积分器的设计

为提高双斜率积分ADC中模拟输入信号转换成数字信号的准确性,设计了一种高性能开关电容积分器以替代传统的RC有源积分器。该开关电容积分器的运算放大器由折叠共源共栅输入级和Class AB输出级组成,开关部分选用CMOS开关,以抑制电荷注入和时钟馈通的影响。在中芯国际0.18μmCMOS工艺下,采用EDA仿真软件对相关模块进行仿真验证,得到运算放大器的直流增益为110.3 dB,单位增益带宽为5.64 MHz,相位裕度达到79°,输出摆幅为0.013 3～3 299 mV,转换速率为7.56 MV/s。结果表明,开关电容积分器完全满足双斜率积分ADC的实际应用。

Design of switched capacitor integrator used in dual-slope integrator

Aimed at improving the accuracy of the analog-digital conversion in dual-slope ADCs,this paper introduces a high-performance switched-capacitor integrator to replace the conventional active RC integrator.The operation amplifier in this switched-capacitor integrator is composed of a folded cascade input stage and a Class AB output stage and CMOS switches are utilized to suppress charge injection and clock feed-through effects.The simulation of all the circuit modules by EDA simulation software,depending on SMIC 0.18 μm CMOS process,shows that the operation amplifier is capable of a DC gain of 110.3 dB,a unity gain bandwidth of 5.64 MHz,a phase margin of 79°,an output swing of 0.013 3-3 299 mV,and a slew rate of 7.56 MV/s.The switched-capacitor integrator proves quite suitable for the practical applications in the dual-slope ADCs.