Design of Constant Phase Elements for Adjustable Pseudocapacitance by a Single Driving Voltage Using Integrated Unipolar Transistor Fields

Abstract

This paper presents the design of a passive fractional-order element with tunable pseudocapacitance, enabling adaptable circuit behavior without additional power consumption. This is an important feature for modelling and characterization in natural systems, as well as in the field of electrical and electronic engineering, particularly for the design of instrumentation and sensing systems. The proposed topologies are based on integrated unipolar transistor arrays. Two implementations are demonstrated, with fractional orders of 0.22 and 0.5, offering pseudocapacitance adjustment ranges from 65 to 1 670 mikroF/s^0.78 and from 6.7 to 51 mikroF/s^0.5, respectively. Tuning is achieved through a DC bias voltage ranging from 0.8 to 10 V. The devices operate across nearly two decades of frequency, from approximately 100 Hz to 200 kHz, and support signal amplitudes in the hundreds of millivolts. Two application examples highlight their potential: electronic tuning of the center frequency in a fractional-order band-pass filter, and adjustment of the oscillation frequency in a fractional-order oscillator with a fixed 22.5 degrees phase shift between output waves. All concepts and results are experimentally validated in the laboratory.