Low-power and wide-dynamic-range sigma-delta modulator for an ECG acquisition system

An analog front-end circuit system, which includes an adaptive sigma-delta modulator (SDM) with a wide dynamic range and a low power consumption, is proposed for an electroencephalogram acquisition system. The required loop filter for the SDM is implemented using G_m-C integrators, which can significantly reduce power consumption and facilitate flexible coefficient adjustment. The performance of the detection system is also improved by employing an adaptive structure and a dynamic range extension algorithm. The system includes a chopper, an SDM, a digital filter with a chopper, and a calibration unit. Circuit simulation reveals that the dynamic range can be extended by more than 40 dB, and accurate results are achieved by the proposed brain signal acquisition system.