Employment of the Padé approximation for implementing fractional-order lead/lag compensators

Fractional-order lead/lag compensator realizations, using Operational Transconductance Amplifiers as active blocks, are presented in this paper. Two different types of fractional-order transfer functions, derived from the integer-order lead/lag compensator transfer function, are used to describe the behavior of the fractional-order compensator. Both types are approximated using the Padé approximation tool, and are expressed by the same form of rational integer-order transfer function. This means that both types can be implemented using the same active core, which is an important advantage from the design versatility point of view. From the design flexibility point of view, the attractive feature is that both types offer electronic adjustment of their characteristics through the appropriate tuning of the DC bias currents. Simulation results, derived using the Cadence IC design suite and the design kit of the Austria Mikro Systeme 0.35μm CMOS process, are used for evaluating the performance of the presented designs. © 2020 Elsevier GmbH