Measurement of electrical resistivity via four probes is widely used in a variety of applications ranging from geophysical prospecting to silicon wafer manufacture. Electrical resistivity tomography is an extension of this approach and is performed via an array of equi-spaced electrodes mounted into the periphery of a process vessel to map non-intrusively the spatial distribution of resistivities within. The digitized boundary data are 'inverted' by an image reconstruction algorithm to produce a map of the internal resistivity distribution. This paper focuses on the design and operation of flexible electrical resistivity tomography instrumentation for use on laboratory- and plant-scale process equipment.

https://iopscience.iop.org/article/10.1088/0957-0233/7/3/005/pdf

Electrical resistance tomography for process applications

Analogue IC Design: the Current Mode Approach

Integrated-Circuit Fabrication. Active Devices in Integrated Circuits. Passive Components: Diodes, Resistors, and Capacitors. Bias Circuits. Basic Gain Stages. Analog Design with MOS Technology. Operational Amplifiers. Wideband Amplifiers. Analog Multipliers and Modulators. Voltage Regulators. Integrated-Circuit Oscillators and Timers. Phase-Locked-Loop Circuits. Integrated-Circuit Filters. Data Conversion Circuits: Digital-To-Analog Converters. Data Conversion Circuits: Analog-To-Digital Converters. Index.

Bipolar and MOS Analog Integrated Circuit Design

This expanded and thoroughly revised edition of Thomas H. Lee's acclaimed guide to the design of gigahertz RF integrated circuits features a completely new chapter on the principles of wireless systems. The chapters on low-noise amplifiers, oscillators and phase noise have been significantly expanded as well. The chapter on architectures now contains several examples of complete chip designs that bring together all the various theoretical and practical elements involved in producing a prototype chip. First Edition Hb (1998): 0-521-63061-4 First Edition Pb (1998); 0-521-63922-0

The Design of CMOS Radio-Frequency Integrated Circuits: RF CIRCUITS THROUGH THE AGES

Design With Operational Amplifiers And Analog Integrated Circuits

A dual current conveyor based rectifier circuit with low temperature sensitivity is presented. The use of a DC current source to bias the rectifying diodes provides higher temperature stability than previously reported designs. In addition the output offset voltage is easily controlled and adjusted to a minimum low value. >

Temperature independent current conveyor precision rectifier

The current-feedback operational amplifier (CFOA) is a relatively new arrival in the analogue designer's tool kit The first monolithic device was produced by Elantec Inc in 1987 and since then it has intrigued and puzzled many Is it really better than the conventional and well known voltage-feedback operational amplifier (VOA)? How does the CFOA differ in design? What are the applications where it performs better than the VOA and when should the VOA be used in preference to the CFOA? We attempt to give some insight into the design and performance of the CFOA and to answer these questions

Current-feedback operational amplifiers and applications

Current-mode techniques are used to realize improved high-frequency precision full-wave rectifiers (PFWRs). Three alternative topologies are described and compared in performance with the classical operational amplifier (op-amp)/diode PFWR. These are a new op-amp supply current-sensing PFWR, a modified classical op-amp/diode design and a novel current-mirror feedback design. The latter exhibits good DC accuracy and the best frequency response. >

New current-mode precision rectifiers

The current-mode instrumentation amplifier (CMIA) based on op-amp power-supply current sensing offers distinct advantages over conventional architecture designs. The CMIA is studied in detail and the CMRR expression is derived in terms of op-amp and transistor parameters. A good CMRR is shown to depend upon several factors, including the power-supply rejection ratio of the op-amps used in the CMIA. The results obtained are shown to compare well with SPICE simulation and provide valuable design insight for development of the next generation of CMIAs.

Common-mode rejection ratio in current-mode instrumentation amplifiers

A system potentially capable of providing continuous analogue computation of (i) urea concentration, (ii) creatinine concentration and (iii) urea-to-creatinine ratio, important markers for the prediction of renal failure is described. The system utilises two enzyme modified chemical current-conveyors, CCCII+, to obtain the outputs directly related to the urea and creatinine concentrations. The devices have been separately prepared by immobilising urease and creatinine deiminase (CD) enzymes onto the input ISFET surfaces. The primary experimental results of the system demonstrate a linear response covering a normal physiological range of urea between 2.5 and 8.3 mM and creatinine between 44 and 106 μM. We propose that this system has the potential for real-time monitoring and suitable for medical determination for renal dysfunctionality.

F.J. Lidgey

Papers

Temperature independent current conveyor precision rectifier

Current-feedback operational amplifiers and applications

New current-mode precision rectifiers

Common-mode rejection ratio in current-mode instrumentation amplifiers

Measurement of urea, creatinine and urea to creatinine ratio using enzyme based chemical current conveyor (CCCII+)