Fractional-order controllers have gained significant research interest in various practical applications due to the additional degrees of freedom offered in their tuning process. The main contribution of this work is the analog implementation, for the first time in the literature, of a fractional-order controller with a transfer function that is not directly constructed from terms of the fractional-order Laplacian operator. This is achieved using Padé approximation, and the resulting integer-order transfer function is implemented using operational transconductance amplifiers as active elements. Post-layout simulation results verify the validity of the introduced procedure.

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An accurate indication that the bandgap voltage reference (BGR) circuit is settled on its nominal value is essential in analog or mixed signal systems. In this paper, a generic method for accurate bandgap voltage reference (BGR) Ready-Indication (RI) is proposed. A RI signal shows that the BGR operates correctly but also is used to enable PoR circuits when those employ the bandgap voltage to generate the required thresholds. In many low power applications, several systems are periodically switched on and off to save power and to increase battery life. In such systems, most circuits must remain off, while BGR is not in ready mode, saving battery energy. In other critical applications, the Ready-Indicator can ensure that critical systems can be set on and the reference voltage is within the operating range. In this paper, the introduced methodology is applied to different reference voltage generators. Initially, a BGR with Ready-Indication is presented extensively, including post-layout simulations results in 22 nm, while thereafter, the study of this method is extended in other BGR topologies. The universality of the proposed method is proved by verifying the operation in all the BGR topologies under study covering designs in 22 nm and 65 nm and with supply voltages 1.8 V, 1 V, 0.55 V.