A fully integrated continuous-time 50-Hz notch filter with center frequency tunability

A novel continuous-time notch filter based on current steering technique was described in this paper. The second-order notch filter consisted of two integrators, one unity-gain inverter and two alpha blocks that were fully integrated onto a silicon chip. The circuit was implemented in SMIC mixed-signal 0.18nm 1P6M process with the die area of 0.06 mm2. Post-annotated simulation indicated the continuous-time notch filter was capable of providing 55.4dB attenuation for the 50 Hz power line interference and its center frequency was tunable against process variations.

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