一种带有新型纹波抑制环路的电容耦合生物医学仪表放大器

A Capacitively-Coupled Biomedical Instrumentati on Amplifier with Novel Ripple Reduction Loop

设计了一种用于扩增生物电信号的低功耗高精度电容耦合斩波仪表放大器.通过斩波来减少失调和1/f噪声,并且利用带有斩波型Ping-Pong结构自调零拓扑的纹波抑制环路来减小由于调制失调电压和1/f噪声而产生的纹波.利用上述结构,斩波纹波在放大器的输出级可衰减约40dB.采用带有较大时间常数的直流伺服环路可以有效抑制电极失调,同时采用正反馈环路来提高输入阻抗.该仪表放大器采用SMIC 0.18μm CMOS工艺进行设计.针对EEG或ECG等信号的特点,将放大器-3dB带宽设置为1kHz.仿真结果表明,它的等效输入噪声功率谱密度为32nV/,噪声效率因数为2.1,共模抑制比为105dB,并且在1V电压供电下,供电电流达到2.8μA.

This paper describes a low-power precision capacitively-coupled chopper instrumentation amplifier（CCIA）to amplify the bio-potential signals.To reduce the offset and 1/f noise,chopping is employed.And the resulting ripple caused by the up-modulated offset and 1/f noise is suppressed by aproposed ripple reduction loop with chopped Ping-Pong auto-zeroing topology.With the proposed RRL,the chopping ripple at the output stage of the CCIA is attenuated about 40 dB.A DC servo loop（DSL）with a large time constant is employed to suppress electrode offset and a positive feedback loop（PFL）is employed to boost the input impedance.The CCIA is implemented in SMIC 0.18μm CMOS process.To fit applications like EEG or ECG signals,-3 dB bandwidth is set as 1 kHz.Simulation results show that it achieves an equivalent input noise power spectrum density（PSD）of 32 nV/槡Hz,a noise efficiency factor（NEF）of 2.1,CMRR of 105 dB and a supply current of 2.8μA at a 1 Vsupply voltage.