A pulse-based amplifier and data converter for bio-potentials

We present a low-power pulse-based amplifier and data conversion circuit for recording bio-potentials. The circuit is designed for data reduction in neurophysiological sensor and communication systems. A low-power low-noise AC amplifier with an asynchronous delta A/D converter is implemented. The asynchronous delta modulation has the advantage of data reduction, clock-less and no quantization noise. The amplifier gain is 53 dB (bandwidth of 200 Hz-20 kHz) with DC variation rejection. The input-referred rms noise is 2 muV. The delta amplitude in the A/D converter is 0.1 V at 3.3 V voltage supply. The system is fabricated with AMI 0.5 mum CMOS technology. The chip size is 1191 mum by 713 mum. The power consumption with 3.3 V supply is 75.9 muW in static state and 194.7 muW with 60 kbps data conversion rate. A graphic user interface was developed to monitor the transmitted signal in real time.