Capacitive instrumentation amplifier for low-power bio potential signal detection

This paper presents the design of a low-power capacitively-coupled CMOS instrumentation amplifier (INA) for long term bio potential measurement and recording applications. The increased demand for low cost, portable and wearable medical monitoring equipment for EEG (electroencephalogram) and ECG (electrocardiogram) is in turn giving rise to a need for very low power, but high precision, analogue front ends. EEG and ECG signals are differential signals characterized by very low amplitude (up to 100µV for EEG and up to 5mV for ECG), relatively low bandwidth (0.5Hz – 150/300Hz) and a quite noisy environment. We present an instrumentation amplifier that achieves the specifications recommended by the application while lowering as much as possible the power consumption through appropriate design choices. The front end has been designed and simulated using a CMOS 0.35µm AMS process.