A 16-channel low-noise low-power neural recording system-on-chip is presented in this article. A low NEF of 2.93 is achieved with a chopping-based delta-sigma ADC topology to resolve the 1 Hz to 1 kHz frequency band in a continuous operation mode. Sample-level duty-cycling mode is proposed to scale down system power consumption by 98.4% for the 0.001 Hz to 1 Hz bandwidth while maintaining the same effective LSB and a high input impedance of 435 MOhm. The combination of these two operation modes expands the system's bandwidth coverage and enables versatile electrophysiological recordings on a single chip.