Power line noise suppression using N-path notch filter for EEG

Power line noise is one of critical problems in biosensing. Various approaches utilizing both analog and digital techniques has been proposed. However, these approaches need active circuits with wide dynamic range. This paper proposes the use of N-path notch filter as a power line noise filter. However, the notch depth in a conventional N-path notch filter is limited by the number of path. A new N-path notch filter with additional sample-and-hold (S/H) circuit is proposed. Simulation results using 0.18um CMOS process parameter show a more than a 40-dB suppression is achieved using the proposed circuit. Negative resistance is applied to reduce the total capacitance by approximately 90%.