Showing papers on "Equivalent circuit published in 1980"

Corrosion Rates from Impedance Measurements: An Introduction

Abstract: The majority of published papers dealing with electrochemical impedance measurements adopt a mathematical approach; this has tended to make the subject somewhat esoteric. Here the subject is dealt with in terms of basic impedance concepts and how these may be used to interpret data in relation to a simple equivalent circuit. This is then extended to cover equivalent circuits containing elements exhibiting diffusion controlled behaviour. A range of experimental techniques which may be used to obtain impedance measurements, together with a new corrosion monitor based on the ‘tangential impedance’ technique, are explained. Graphical methods of data interpretation are given that avoid excessive numerical manipulation and which also allow the charge transfer resistance to. be extracted from systems exhibiting mixed diffusion–charge transfer control.

Modern Transmission Line Theory and Applications

Abstract: Presents the latest methods for properly considering transmission line effects as well as the calculation of transmission line properties as a function of materials and geometries. Emphasizes properties of stripline and microstrip circuits, explaining that at high enough frequencies, almost every interconnection in a circuit will exhibit transmission line properties. ., that, if these circuits are to be well designed, the transmission lines in the circuit must be appropriately treated as part of the circuit . .and that it is no longer possible to separate the transmission line user from the transmission line designer--not only are the lines present, but their properties are functions of the circuit layout itself. Requires an understanding of distributed circuits, wave propagation, and the constant interplay between field variables and circuit variables that takes place in all distributed circuits at high frequencies.

Electromagnetic transmission through narrow slots in thick conducting screens

Abstract: The general formulas for electromagnetic transmission through an infinitely long slot in a perfectly conducting screen of finite thickness are specialized to the case of a narrow slot. The slot may be filled with a homogeneous isotropic material. A simple equivalent circuit for the narrow slot is developed. It is found that for certain screen thicknesses the slot becomes resonant, and exceptionally large transmission of energy may occur. In fact, as the slot width approaches zero, the transmission width at resonance becomes 1/\pi wavelengths regardless of the actual slot width. The effect of loading the slot with a lossy dielectric is also considered. Computations are given to illustrate the validity of the equivalent circuit model and the accuracy of transmission characteristics computed from it.

Insulated-gate planar thyristors: I—Structure and basic operation

Abstract: A high-voltage planar triac which is controlled by an insulated-gate terminal is described. Its structure is related to the DMOS transistor on which it is based and its multiple operating modes are discussed in terms of an equivalent circuit composed of MOS and bi-polar transistors and resistors. A typical junction-isolated device has a 150-V breakdown and an on-resistance less than 10 Ω for a 400-µm-wide channel. The on-resistance can easily be scaled to very low values simply by increasing the device width. Extension of the MOS thryistor concept to other devices and higher voltages is described. Quantitative analysis and modeling of these new devices are described in a companion paper.

Analytical and numerical techniques for analyzing an electrically short dipole with a nonlinear load

Abstract: An electrically short dipole with a nonlinear dipole load is analyzed theoretically using both analytical and numerical techniques. The analytical solution is given in terms of the Anger function of imaginary order and imaginary argument and is derived from the nonlinear differential equation for the Thevenin's equivalent circuit of a dipole with a diode. The numerical technique is to solve the nodal equation using a time-stepping finite difference equation method. The nonlinear resistance of the diode is treated using the Newton-Raphson iteration technique. A comparison between the analytical and numerical solutions is given.

Yield optimization for arbitrary statistical distributions: Part II-Implementation

Abstract: A suggested test problem for proposed algorithms in yield optimization is described in detail. The problem is a current switch emitter follower (CSEF) circuit originally described by Ho, which includes a transmission line. The ideas presented in Part I of this paper [1] are applied to this circuit in order to obtain an optimal statistical design. Production yield is maximized taking into consideration statistical distributions of circuit parameters and realistic correlations between transistor model parameters. Nonlinear programming employing the analytical formuias for yield and its sensitivities is used to provide optimal nominal values for the circuit parameters. Different design specifications are assumed and corresponding optimal designs are obtained.

Differential to single-ended converter utilizing inverted transistors

Abstract: A differential to single-ended converter circuit is disclosed which utilizes integrated injection logic device geometrics to significantly reduce the area required to fabricate the converter within an integrated circuit. Inverted transistor operation and multiple collector output terminals allow the converter circuit to directly drive integrated injection logic circuitry which may be fabricated within the same integrated circuit chip. When used in conjunction with a voltage comparator circuit, the differential to single-ended converter circuit maintains the offset associated with the comparator circuit at a minimum despite variations in operating temperature and variations in integrated circuit processing.

Method of digital logic simulation

Abstract: A logic simulation is executed using a real circuit as a part of a simulation model of a logic circuit subjected to the logic simulation. The simulation model is formed of the real circuit and a simulation circuit, and the operation of the real circuit and the logic simulation of the simulation circuit are performed alternately. The operation of the real circuit is performed in response to an input signal thereto representing the condition of the output node of the simulation circuit, while the logic simulation of the simulation circuit is executed in response to a stimulus in the form of an output signal of the real circuit which is applied to the input node of the simulation circuit.

Field analysis for rotating induction machines and its relationship to the equivalent-circuit method

Abstract: This paper presents a field analysis for rotating induction machines which includes the effects of rotor skew, and accurately models the discrete nature of the rotor curent. It is verified by comparison with the conventional equivalent-circuit method, and by using it to derive the equivalent-circuit for a balanced 3-phase skewed-rotor induction machine.

Semiconductor switching circuit with clamping and energy recovery features

Abstract: A circuit for holding the voltage across a rapidly switched semiconductor element such as a transistor used in an inductive circuit to substantially twice the voltage of an input source when the element is switched to its nonconducting state. Also included is circuitry for recovering and returning to the input source the energy stored in the inductance and wiring of the inductive circuit.

Josephson-junction mixer analysis using frequency-conversion and noise-correlation matrices

Abstract: A complete characterization and optimization have been carried out for an externally pumped Josephson-junction mixer. A noise-driven nonlinear pump equation is first solved in the time domain on a computer in order to obtain a conversion matrix and noise-correlation matrix for the small-signal current and voltage. A set of linear circuit equations formed by the matrices is then solved in the frequency domain for the mixer noise temperature and conversion efficiency. Finally, optimization is made with respect to circuit, bias, and junction parameters to find the ultimate theoretical performance.

A spring model and equivalent neural network for arm posture control

Abstract: A model is introduced for the motor program which controls final position. The first part of the model relates the biomechanical properties of the muscles to the EMG activities of the extensor and flexor muscles and thereby generates quatitative predictions for the relationships between the EMGs, final position, external forces, muscle stiffness, and muscle tension. To the extent that comparable data exist, the model is shown to give correct quantitative predictions. When only qualitative comparisons can be made, the model is consistent with the data in the literature. The model is complete and can be tested quantitatively in detail in the future. An equivalent circuit for the neural network that innervates the muscles is given. It is shown to have the advantages of making the programming of final position simple to either compute or lookup in a table. In addition, new situations, such as adapting to a force, or an unusual viewing angle, lead to very simple changes in the basic program in terms of the equivalent circuit.

Equivalent circuit model of FET including distributed gate effects

Abstract: A model is presented which takes into account the distributed nature of the gate in microwave field-effect transistors (FET's). The model is used to derive an expression for the equivalent gate impedance. The result is suitable for determining the reduction in the available gain tlue to gate losses.

Subscriber line interface circuit with impedance synthesizer

Abstract: A subscriber line interface circuit is described wherein the transverse and longitudinal termination impedances may be independently controlled; and wherein the equivalent termination impedance of a subscriber line/trunk as appears to the central office can be adjusted upward or downward from a lower resistance value, with longitudinal balance (also known as the common mode rejection) being determined by the matching of feed resistors. The foregoing interface circuit is implementable as a monolithic integrated circuit having low power dissipation, improved power bandwidth requirements, and lower voltage breakdown requirements for integrated circuits; all resulting in an improved telephone line interface circuit. Voltage feedback or current feedback may be employed in a circuit to synthesize the proper ac transverse termination impedance from a known dc resistance, for example, from the feed line resistors in a telephone line circuit.

MOS crystal oscillator design

Abstract: The operation of MOS crystal oscillators is investigated assuming near-sinusoidal AC voltages at gate and drain. It is shown that the circuit operation depends basically on only two normalized parameters. Computer solution is used to produce a series of normalized curves allowing oscillator design for prescribed start-up conditions, steady-state amplitude, and operating current. The theoretical predictions agree closely with measurements on sample circuits.

Theory of dielectric-filled edge-slot antennas

Abstract: A theory has been developed for dielectric-filled edge-slot (DFES) antennas which belong to a class of circumferential slot antennas that are suitable for conformal mounting on conducting bodies of revolution. The specific antenna considered consists of a disk of dielectric substrate mounted between the two halves of a conducting cylinder and is excited at its center by a coaxial stub. It can be tuned for a desired operating frequency with the help of a number of axially oriented passive metallic posts located inside the dielectric region. For analysis, the antenna is modeled as a symmetrically excited E -type radial waveguide loaded with the metallic posts and terminated by an equivalent admittance appropriate for the radiating aperture. Circuit parameters for the metallic posts in the radial waveguide are obtained by detailed field analysis using mode matchng techniques. These are then used, along with the equivalent transmission line circuit for the antenna, to obtain the input reflection coefficient as a function of frequency for various DFES antennas. The results of computations based on the theory developed are compared with available measured values.

Loading apparatus for testing a power supply

Abstract: Loading apparatus for testing a power supply comprises an electronic load circuit, the electronic load circuit comprising an organically and systematically connected mode switching circuit capable switching from and to one another a constant resistance mode, a constant current mode and a slave mode. A load switching circuit is connected to the mode switching circuit and an error amplifier is adapted to input a voltage signal in each of the modes. A field effect transistor circuit is adapted to receive the output of the error amplifier as a gate control signal and has a drain terminal to which is fed the output from a power unit under test and further has a source terminal, the output of which is fed back as a comparison voltage signal to the error amplifier. A current measurement display circuit is branched to the source terminal of the field effect transistor circuit, and an overpower protection warning circuit is also branched to the source terminal. A voltage measurement display circuit is connected to the drain terminal, and a switching time setting circuit is provided for setting an automatic switching time in the load switching circuit.

Tuneable I.C. active integrator

Abstract: An I.C. integrator circuit is provided with an active tuneable element by which a precise integrator time constant can be established, despite variations in the values of individual circuit components. A plurality of integrator circuits are connected in an overall frequency responsive circuit, each integrator circuit having a input transconductance stage, an output integrating stage, and an adjustable intermediate conditioning stage, the latter stage preferably comprising a Gilbert multiplier circuit. The time constant of each integrator circuit is controlled by the conditioning stage, which in turn is under the control of a bias circuit common to all of the integrator circuits. A desired net frequency response characteristic can be achieved by simple adjustments to the common bias circuit, despite normal tolerances and variations among individual integrator circuits. The circuit is completely integrated, is capable of operating at audio as well as at higher frequency ranges, has a greater tuneable range than prior art devices, and is highly linear.

Calculation of hopping transport coefficients

Abstract: The calculation of d.c. conductivity, a.c. conductivity, magnetoresistance and Hall mobility from the Miller–Abrahams equivalent circuit is reviewed. Analytical formulae are derived by making simpl...

Theory of microwave coupled-line networks

Abstract: The multiwire line forms the basis of many practical microwave filtering and coupling circuits. It also has considerable importance as a circuit element in formal synthesis procedures. This paper is concerned with a tutorial presentation of the various methods of analysis for such multiwire lines leading to a number of different equivalent circuits, and with the use of these for synthesis and design. The treatment is restricted to the case of uniform commensurate lines with homogeneous dielectric. Where possible, a unifying approach based on general equivalent circuits is used and this permits the design of some well-known microwave structures to be seen from a somewhat different viewpoint. Some gaps in the existing design procedures for some components are identified and it may be that the methods of analysis and synthesis presented here could lead to new solutions.

Determination of the Electrode Capacitance Matrix for GaAs FET's

Abstract: In this paper, a method is presented which provides the electrode capacitance matrix for GaAs FET's The method incorporates a Green's function, valid for conductors printed on or embedded in a grounded substrate, with the moment method technique Although calculations for various geometries of printed conductors are considered, emphasis is placed on the computation of self- and mutual-capacitances for the source, gate, drain equivalent circuit of a GaAs FET As an example, the speed power characteristics of a depletion-rnode GaAs FET inverter circuit are examined, as a function of device width, pad and gate length

A general four-terminal charging-current model for the insulated-gate field-effect transistor—I

Abstract: A general form of equivalent circuit model for the IGFET is presented in which a complete representation is given of the charging currents in the device At the heart of the model is the essential step of “partitioning” the channel charging current between the source and drain terminals This is carried out in terms of the distinct physical mechanisms associated with the charging of the device via the gate and substrate terminals respectively The circuit elements of the model are all defined on a quasi-static (charge control) basis by the relationships between the charges stored in the IGFET and the voltages applied to its four terminals

Computer-aided characterization of TEM transmission lines

Abstract: A method of characterizing a multiconductor transmissionline system, which supports transverse-electromagnetic (TEM) waves traveling at different velocities, has been developed. The method combines equivalent circuit concept and optimization search technique. It is shown that the coupled transmission-line parameters can be computed from a set of wave velocities and transformer ratios that characterize the decoupled equivalent network of the multiconductor system. A combination of the steepest descent and Fibonacci-search algorithms for determining the wave-propagation velocities from frequency-domain measurements has been formulated, along with an alternative method of computing the inductance parameters from the measured characteristic admittances and static capacitances. For illustration, numerical examples and experimental results are given.

Transmission line model of the interaction of a long metal wire with the ionosphere

Abstract: An equivalent electric circuit model is used to study the electrodynamic interactions of long orbiting metallic tethers with the ionospheric plasma and, in particular, to derive current and potential profiles along bare metallic tethers. In contrast with other models, this approach is dynamic, enabling both the transient behavior of the wire and its final equilibrium state to be derived. A comparison with the results of other models indicates the advantage of the present approach, especially in those cases where the internal resistance of the tether plays a major role in determining the current and potential distributions.

An X-band SOS resistive gate—insulator—semiconductor (RIS) switch

Abstract: The new X-Band Resistive Gate-Insulator-Semiconductor (RIS) switch has been fabricated on silicon-on-sapphire, and its equivalent circuit model characterized. An RIS SPST switch with 20-dB ON/OFF isolation, 1.2-dB insertion loss, and power-handling capacity in excess of 20-W peak has been achieved at X band. The device switching time is on the order of 600 ns, and it requires negligible control holding current in both ON and OFF states. The device is compatible with monolithic integrated-circuit technology and thus is suitable for integration into low-cost monolithic phase shifters or other microwave integrated circuits.

Oscillator circuit with digital temperature compensation

Abstract: An oscillator circuit having a digital temperature compensation circuit which contains two low frequency quartz oscillators, a beat frequency generator and a correction circuit and a logic circuit selectively controlling an addition circuit. The beat frequency generator receives the frequencies generated by the low frequency oscillators. The difference between the low frequencies is fed into the correction circuit which in turn cooperates with the logic circuit. The beat frequency generator is controlled by a high frequency oscillator having an integrated RC circuit and the correction circuit has a PROM in which the correction functions are stored. The selectively controlled addition circuit acts on the output signal of the first oscillator and corrects the frequency thereof. An oscillator circuit connected in such a manner requires no pre-selection of the quartz crystals in pairs and the correction may be effected by influencing the high frequency oscillator, whereby a high degree of accuracy may be obtained.

Zirconia Oxygen Sensor - An Equivalent Circuit Model

Abstract: The zirconia exhaust gas oxygen sensor is a key component in closed loop engine emissions control systems. An equivalent circuit model of the sensor is derived from fundamental electrochemical principles. In this model, sensor electrode resistance and capacitance are separated from the zirconia electrolyte resistance. Numerical examples are given to show how the equivalent circuit can be used to model both steady state and transient characteristics of sensors.

A Coupling Model for a Pair of Skewed Transmission Lines

Abstract: A coupling model in the form of an equivalent circuit is developed for a pair of skewed transmission lines. The inductive coupling is evaluated in closed form and the capitances are obtained from the solution of a pair of coupled integral equations for the excess-charge distributions along the transmission lines. The coupled integral equations for the excess charges are solved by an approximate analytical method and also by employing the method of moments. The two solutions are seen to be in excelent agreement. The excess-charge distributions are then used in a parametric study of the capacitances in the coupling model. The results are presented in graphical form.

Numerical technique for determining pumped nonlinear device waveforms

Abstract: The letter presents an efficient technique for determination of voltage and Current waveforms when a microwave network containing one or more nonlinear elements is excited by a sinusoidal source. This algorithm is a generalisation of an approach previously reported by Gupta and Lomax and features a ready application to microwave networks represented by a large number of equivalent circuit elements, either lumped or distributed.

Nonlinear-linear analysis of microwave mixer with any number of diodes

Abstract: A theory is presented for analyzing mixers with any number of diodes. Both the nonlinear and linear steps of the analysis are included. The diodes are characterized by both nonlinear conductance and nonlinear capacitance. Any linear embedding network is allowed. It is assumed that both the parameters of the linear part of a mixer circuit and the parameters of the diodes are known. This general approach to microwave circuits with diodes, which is a qualitatively new problem in circuits analysis, allows to investigate any diode mixer with deep insight into its operation. A computer program has been developed to perform the analysis and all computations. The program has been utilized to analyze a crossbar mixer configuration which exhibits extremely encouraging performance. Some computed results are presented herein.