This paper presents a 1.2 V low-power low-noise analog front end circuit for electrocardiogram (ECG) applications. The proposed system architecture is optimized to achieve a better trade-off between power consumption and noise figure. A low noise instrumentation amplifier with tunable pseudo-resistor, a programmable gain stage, and a low-pass Gm-C filter are adopted. For the purpose of the accurate cut-off frequency of the low-pass filter, a novel self-calibration circuit is employed. The AFE consumed 7μW and 0.5~100Hz input-referred integrated noise is 4.5 μVrms in a 0.13 μm CMOS technology.