A low-power CMOS front-end for cuff-recorded nerve signals

A low-power signal sensor front-end for biomedical applications is presented. The front-end consists of a preamplifier and an AID converter (ADC) for quantizing the sensor readout signal. The amplifier achieves low thermal noise by utilizing the weak inversion biasing region of MOSTs and low I/f-noise by chopper modulation. The resulting equivalent input referred noise is 7 nV/Hz, for a chopping frequency of 20 kHz. The implemented gain is 72.5 dB over a signal bandwidth of 4 kHz. The ADC is implemented as a third order ΣΔ-modulator employing a continuous-time (CT) loop filter. The loop filter integrators are implemented as G^m - C elements. The ADC signal-to-noise- and-distortion-ratio (SNDR) is measured to 62 dB, equivalent to 10 bits performance over a 4 kHz bandwidth and a dynamic range (OR) of 67 dB. The systems draws 353 μW of power from a modest supply voltage of 1.8 V.