Power-Efficient Electronically Tunable Fractional-Order Filter

Abstract

This article describes a low-voltage, low-power fractional-order low-pass filter (FO-LPF) of order 1 + α, which is implemented using a voltage differencing differential difference amplifier (VDDDA). The VDDDA structure is implemented using the bulk-driven metal oxide semiconductor transistor technique. The transistors operate in the subthreshold region to maintain low-supply voltage and low-power consumption. The FO-LPF structure implemented using this VDDDA structure is compact. It includes three VDDDAs and three grounded capacitors along with two active resistors implemented using MOS transistors. In addition, this filter structure provides electronic tuning of its order and cut-off frequency through the bias current of the active component used. The effects of tracking error and parasitics on the functionality of the proposed FO-LPF were investigated. The VDDDA and filter operate at ±300 mV and dissipate only 207 nW and 663 nW of power, respectively. Thus, the VDDDA structure and filter are suitable for low-voltage and low-power operation. Layouts of the proposed VDDDA as well as the FO-LPF were designed in the Cadence Virtuoso environment. Post-layout simulation results of the designed circuits imply that they are suitable for fabrication. Noise, total harmonic distortion, Monte-Carlo, and PVT analyses were also performed.

Digitally Controlled Fractional-Order Elements Using OTA-C Structures

“…In order to construct a fractional-order capacitor, we have started with a fractionalorder differentiator with the transfer function H(s) = (τs) α , where τ = 1/ω 0 is defined in Equation (4). It can also be concluded that the impedance Z(s) of CPE and FOI at the centre frequency ω 0 is equal to 1/g mVI .…”

“…To achieve a wider bandwidth, a higher-than-second-order approximation is required. The wider bandwidth would then be useful for the design of FO filters [3,4]. To properly design an FO filter, its cut-off frequency must be lower than the operating range of the CPE.…”

“…They efficiently describe processes in control theory, material theory, diffusion theory, robotics, signal processing, viscoelasticity, etc. The wide range of applications includes electrical filters [3,4], analogue modelling of bioimpedance [5], emulation of an electrical analogue model of the human body [6], food quality [7], DC-DC converters [8], applications in control theory for drive motors [9], analogue modelling of supercapacitors [10], analogue modelling of lithium batteries in electric vehicles [11], and many others.…”