This paper presents a multi-channel biomedical sensor system with system-level chopping and stochastic analog-to-digital (A/D) conversion techniques. The system-level chopping technique extends the input-signal bandwidth and reduces the interchannel crosstalk caused by multiplexing. The system-level chopping can replace an analog low-pass filter (LPF) with a digital filter and can reduce its area occupation. The stochastic A/D conversion technique realizes power-efficient resolution enhancement. A novel auto-calibration technique is also proposed for the stochastic A/D conversion technique. The proposed system includes a prototype analog front-end (AFE) IC fabricated using a 130nm CMOS process. The fabricated AFE IC improved its interchannel crosstalk by 40dB compared with the conventional analog chopping architecture. The AFE IC achieved SNDR of 62.9dB at a sampling rate of 31.25kSps while consuming 9.6µW from a 1.2V power supply. The proposed resolution enhancement technique improved the measured SNDR by 4.5dB.