Stephan J. G. Gift

Bio: Stephan J. G. Gift is an academic researcher from University of the West Indies. The author has contributed to research in topics: Operational amplifier & Current-feedback operational amplifier. The author has an hindex of 20, co-authored 86 publications receiving 1072 citations. Previous affiliations of Stephan J. G. Gift include University of Calgary.

A high-performance full-wave rectifier circuit

Abstract: A new circuit that enables basic operational amplifiers (op amps) such as the LM741 to produce precise full-wave rectification for frequencies up to and exceeding 100 kHz without waveform distortion is presented. The circuit is based on a standard op amp precise rectifier that is modified by the inclusion of a current conveyor to improve the rectifying process.

Versatile Precision Full-Wave Rectifiers for Instrumentation and Measurements

Abstract: This paper analyzes the performance of a family of high-quality precision full-wave rectifiers that utilize operational conveyors. The circuits have high precision, wide bandwidth, and high accuracy and are superior to the corresponding operational-amplifier (op amp)-based circuits. Using the LF351 op amp, they are able to rectify signals up to 100 kHz and beyond with little or no distortion. PSPICE results for the circuits are presented.

An enhanced current-mode instrumentation amplifier

Abstract: An enhanced current-mode instrumentation amplifier is presented. The circuit is based on a current conveyor-operational amplifier combined configuration that offers significant improvement in accuracy as compared with the basic current-mode instrumentation amplifier based on current conveyors only.

On a multivibrator that employs a fractional capacitor

Abstract: The simple free running multivibrator built around a single fractional capacitor is examined in this letter. Equations for the oscillation frequency of the multivibrator are derived taking into account the positive feedback factor around the multivibrator. We show that the use of the fractional capacitance allows the multivibrator to have very high frequencies of oscillation for reasonable time constants used. PSPICE simulation and experimental results demonstrate the analysis with an approximation to a fractional capacitor that yields a result, which is at least 1000 times in frequency compared to if a normal capacitor of the same value was employed.

Active Elements for Analog Signal Processing: Classification, Review, and New Proposals

Abstract: In the paper, an analysis of the state-of-the-art of active elements for analog signal processing is presented which support - in contrast to the conven tional operational amplifiers - not only the voltage-mode but also the current- and mixed-mode operations. Several pro blems are addressed which are associated with the utiliza tion of these elements in linear applications, particularly in frequency filters. A methodology is proposed which generates a number of fundamentally new active elem ents with their potential utilization in various areas o f signal processing.

Fractional-order circuits and systems: An emerging interdisciplinary research area

Abstract: A recent article published in this magazine has labeled fractional-order continuous-time systems as the "21st century systems". Indeed, this emerging research area is slowly gaining momentum among electrical engineers while its deeply rooted mathematical concepts also slowly migrate to various engineering disciplines. A very important aspect of research in fractional-order circuits and systems is that it is an interdisciplinary subject. Specifically, it is an area where biochemistry, medicine and electrical engineering over-lap giving rise to many new potential applications. This article aims to provide an overview of the current status of research in this area, highlighting specific problems which need to be addressed particularly by electrical engineers.

Theory, technology and applications of piezoresistive sensors: A review

Abstract: Sensors based on the detection of small resistance variations are universally recognized as piezoresistive. Being one of the simplest, most common and most investigated classes of sensors, continuous efforts are focused on creating improved devices with higher performance that can be used in many commercial and non–commercial applications (e.g. evaluation of strain, pressure, acceleration, force etc.). Consequently, despite the fact that more than 150 years have passed since the discovery of the piezoresistive effect in some classes of metals and semiconductors, the development of such sensors remains interesting and topical. Moreover, with the advent of second–generation robotics, research on piezoresistive sensors has undergone a massive increase. This paper aims to be a short, self–consistent vademecum which would be useful to researchers and engineers, since it focuses on the fundamentals of theory, materials, and readout–circuit design pertinent to the most recent developments in the field of piezoresistive sensors.

Improved laser test of the isotropy of space

Abstract: Extremely sensitive readout of a stable "etalon of length" is achieved with laser frequency-locking techniques. Rotation of the entire electro-optical system maps any cosmic directional anisotropy of space into a corresponding frequency variation. We found a fractional length change $\frac{\ensuremath{\Delta}l}{l}=(1.5\ifmmode\pm\else\textpm\fi{}2.5)\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}15}$, with the expected ${P}_{2}(cos\ensuremath{\theta})$ signature. This null result represents a 4000-fold improvement on the best previous measurement of Jaseja et al.