Current Feedback Instrumentation Amplifier With Built-In Differential Electrode Offset Cancellation Loop for ECG/EEG Sensing Frontend

Abstract

This work describes a compact and low-power current feedback instrumentation amplifier (CFIA) that can effectively eliminate differential electrode offset (DEO), amplifier input offset, and light motion artifacts. The proposed approach is using a local feedback loop in the first stage of the CFIA which can eliminate dc and low frequency offset whereas by-passes useful components such as EEG and ECG signals. As a result, the DEO and amplifier input offset can be eliminated in the first stage of the CFIA while still amplifying the desired signal components. This enables offset cancellation operation with low bias current that leads to higher energy efficiency compared to existing CFIA offset cancellation schemes. The proposed CFIA is implemented using CMOS 0.18-μm technology, that can eliminate up to 250-mV DEO with a supply voltage of 1.8 V. Measurement results show common mode rejection ratio (CMRR) 120 dB (without DEO) and 95 dB (with DEO of 250 mV) at 10 Hz, input noise 3.8 μVrms, power consumption 12.7 μW, and NEF 39 with core area of 73.6 × 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-3</sup> mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> . Furthermore, the actual EEG and ECG waveforms are obtained using the proposed CFIA under an actual clinical setting.