A Low-Noise and Low-Power Multi-Channel ECG AFE Based on Orthogonal Current-Reuse Amplifier

This paper proposes a low-noise and low-power current-reuse analog front-end (AFE) for multi-channel electrocardiography (ECG) acquisition. A new low-power orthogonal recombination method is proposed in the four-channel current-reuse amplifier, which reduces the recombination current by half and cuts down the power supply voltage while ensuring the crosstalk suppression capability, resulting in a lower average channel power consumption. A four-order current-cancellation subthreshold-source-follower low-pass filter (CS-LPF) is proposed in this paper, which realizes the reduction of the chip area and power consumption by cross-coupling current cancellation technology. In addition, the input impedance boosting circuit, DC servo loop (DSL), and successive approximation register analog-to-digital converter (SAR-ADC) are designed in the proposed AFE, and it can record and quantify ECG signals. The presented AFE was implemented in a 65nm CMOS process, and the core area is 1.42mm
$\times 0.85$
mm. The measured results show that the proposed AFE has a variable gain of 40.5-56dB. The fully differential low-pass filter with a power consumption of only 4.8nW achieves 50% capacitance reduction. The average power consumption per channel of the proposed AFE is only
$2.6\mu \text{W}$
, and the power efficiency factor (PEF) and noise efficiency factor (NEF) are 3.93 and 1.81 respectively.