一种用于高精度电容传感器电路的三级运算放大器

A Three-Stage Operational Amplifier for High Precision Capacitance Sensor Circuit

为提高电容式传感器专用集成电路(ASIC)的检测精度,设计了一种三级运算放大器电路。该放大器电路为全差分实现形式,采用三级共源放大器级联结构,使用密勒补偿并调整零点抵消高频极点,以保证放大器的稳定性。该放大器电路基于0.18μm标准CMOS工艺设计实现,工作电压为1.8 V,工作电流为80μA。电路仿真结果显示:三级运算放大器的直流增益为118 dB,单位增益频率为73 MHz,噪声水平为0.21μV/√Hz。芯片测试结果表明,采用该放大器的电容传感器电路前端的非线性优于6×10^(-5)。该放大器功耗低、面积小、可靠性好,在工程上实现了较优的综合性能。

In order to increase the detection accuracy of the capacitance sensor application specific integrated circuit(ASIC),a three-stage operational amplifier circuit was designed.The amplifier circuit adopted a cascade structure of three common source stages and was designed as fully differential type.Miller compensation and the tuning of zero to cancel the high-frequency pole were used to guarantee the stability of the amplifer.The amplifier circuit was designed and implemented based on standard 0.18μm CMOS process.The operating voltage is 1.8 V,and the operating current is 80μA.Circuit simulation results show that the DC gain of the three-stage operational operational amplifier is 118 dB,the unity gain frequency is 73 MHz,and the noise level is 0.21μV/√Hz.Chip test results show that the nonlinearity of the front end of the capacitance sensor circuit using this amplifier is better than 6×10^(-5).The amplifier has low power consumption,small area and good reliability,and achieves better comprehensive performance in engineering.