Simple MOS Transistor-Based Realization of Fractional-Order Capacitors

A new second-order MOS transistor based circuit block approximating the behavior of a fractional-order capacitor is proposed. The circuit is modular and therefore the order of the approximation can be increased by more stages of the same circuit in cascade or in parallel. Simulation results using a TSMC 65nm CMOS technology are provided and show less than 2° of phase error in two decades around the center frequency of the approximation. Experimental results of realized fractional-order capacitors and of a fractional-order relaxation oscillator are also shown.