A new current-mode square-root-domain notch filter

In this paper, a new current-mode second-order square-root-domain notch filter is proposed. The design is based on the state-space synthesis method with two subcircuit; square-root and squarer/divider circuits. In the circuit, the input and the output values, and dominant variables are all currents. Only MOS transistors and grounded capacitors are required to realize the filter circuit. Three cases of the second-order notch filter were obtained. The regular notch was obtained when omega_n = 3D omega_p, the lowpass notch was obtained when omega_n > omega_p, and the highpass notch was obtained when omega_n < omega_p. The center frequency, and the notch frequency of the filter can be electronically tuned by changing external currents. Time and frequency domain simulations are performed using PSPICE program for the filter to verify the theory and to show the performance of it. For this purpose, the filter is simulated by using TSMC 0.35 mum Level 3 CMOS process parameters.