Current-mode capacitorless integrators and differentiators for implementing emulators of fractional-order elements

Fractional-order capacitor and inductor emulator, implemented using current-mirrors as active elements and MOS transistors as capacitors, is introduced in this paper. Current-mirror integrators are used for performing the required current-mode integration/differentiation operation within the emulator stage. Also, a voltage-to-current converter, implemented using an Operational Transconductance Amplifier, is utilized for realizing the required interface of the input signal. Thus, the proposed emulator is simultaneously capacitorless and resistorless and offers the advantage of electronic tuning of the characteristics as well as of the type of the emulated fractional-order element. In addition, a modified version of the emulator that allows current excitation is proposed. The evaluation of the behavior of the proposed schemes has been performed using the Cadence IC design suite and the Design Kit provided by the Austrian Micro Systems 0.35 μm CMOS process.