A Low-Voltage Chopper-Stabilized Amplifier for Fetal ECG Monitoring With a 1.41 Power Efficiency Factor

This paper presents a low-voltage current-reuse chopper-stabilized frontend amplifier for fetal ECG monitoring. The proposed amplifier allows for individual tuning of the noise in each measurement channel, minimizing the total power consumption while satisfying all application requirements. The low-voltage current reuse topology exploits power optimization in both the current and the voltage domain, exploiting multiple supply voltages (0.3, 0.6 and 1.2 V). The power management circuitry providing the different supplies is optimized for high efficiency (peak charge-pump efficiency $= 90\%$ ).The low-voltage amplifier together with its power management circuitry is implemented in a standard $0.18~\mu{\rm m}$ CMOS process and characterized experimentally. The amplifier core achieves both good noise efficiency factor $({\rm NEF}=1.74)$ and power efficiency factor $({\rm PEF}=1.05)$ . Experiments show that the amplifier core can provide a noise level of $0.34~\mu {\rm Vrms}$ in a 0.7 to 182 Hz band, consuming $1.17~\mu {\rm W}$ power. The amplifier together with its power management circuitry consumes $1.56 ~\mu {\rm W}$ , achieving a PEF of 1.41. The amplifier is also validated with adult ECG and pre-recorded fetal ECG measurements.