Design of Tunable Low-Power Band-Stop Filter for Elimination of 50 Hz Power-Line Noise

The electrocardiogram is affected by various noises and one of the most important of which is 50 Hz power-line noise. On the other hand, it is necessary to use a battery in the portable device and so it requires the use of low power consumption circuits. Therefore, one of the challenges ahead when designing this type of device is the use of energy-saving filters with the ability to integrate devices and attenuate unwanted signals properly. This paper presents a low-power tunable sixth-order band-stop filter that does not need the off-chip capacitors. The filter structure is based on operational transconductance amplifiers (OTA) and integrated capacitors. Also, it is possible to change the central attenuation frequency of the proposed filter using bias voltage of the transconductance amplifiers. The proposed band-stop filter is designed and simulated in 180 nm CMOS technology at the transistor level. The simulation results show that the proposed filter can attenuate unwanted signals at 50 Hz by 102 dB while the maximum capacitance used in the filter is 54 pF. The power consumption of the proposed band-stop filter is 13.1 nW at a supply voltage of 1.8 V.