A Review on Recent Development of Input Impedance Boosting for Bio-Potential Amplifiers

Bio-potential signals like Electrocardiogram(ECG) and Electroencephalogram(EEG) are recorded routinely in modern clinical practice and daily life, providing helpful information for early diagnosis of disease. A very high input impedance (Zin) of the readout is crucial in emerging applications, e.g. drivers’ monitoring, embedded smart home heath monitoring. This paper gives a review on existing techniques including 1) positive feedback technique; 2) auxiliary path feedforward technique; 3) current feedback topology. This paper focuses on the development on each Zin boosting technique in recent years, like auxiliary capacitor assisted input buffer and current feedback topology with parasitic capacitance shielding of the input transistors, which help to achieve a reliable Gohm input impedance with minimum power consumption.