Showing papers on "Equivalent circuit published in 1995"

Equivalent-circuit model of the squeezed gas film in a silicon accelerometer

Abstract: We present a new electric equivalent circuit for the forces created by a squeezed gas film between vertically moving planar surfaces. The model is realized with frequency-dependent resistors and inductors. Circuit analysis tools are applied to calculate the response of a micromechanical silicon capacitive accelerometer in both the frequency and the time domains. The simulations are shown to match the measured frequency responses in an excellent way. We utilize the circuit model to calculate the effective viscosity in a narrow gap between the moving surfaces. The results are compared with different slip-flow equations discussed in the literature. We present a simple approximate equation of the pressure-dependent viscosity that is valid for both viscous and molecular damping regions, and has 5% accuracy.

Modeling and damping of high-frequency leakage currents in PWM inverter-fed AC motor drive systems

Abstract: This paper presents an equivalent circuit for high-frequency leakage currents in pulsewidth modulation (PWM) inverter-fed AC motors, which forms a series resonant circuit. The analysis based on the equivalent circuit leads to such a conclusion that the connection of a conventional common-mode choke or reactor in series between the AC terminals of a PWM inverter and those of an AC motor is not effective to reduce the rms and average values of the leakage current, but effective to reduce the peak value. Furthermore, this paper proposes a common-mode transformer which is different in damping principle from the conventional common-mode choke. It is shown theoretically and experimentally that the common-mode transformer is able to reduce the rms value of the leakage current to 25%, where the core used in the common-mode transformer is smaller than that of the conventional common-mode choke.

A neural network modeling approach to circuit optimization and statistical design

Abstract: The trend of using accurate models such as physics-based FET models, coupled with the demand for yield optimization results in a computationally challenging task. This paper presents a new approach to microwave circuit optimization and statistical design featuring neural network models at either device or circuit levels. At the device level, the neural network represents a physics-oriented FET model yet without the need to solve device physics equations repeatedly during optimization. At the circuit level, the neural network speeds up optimization by replacing repeated circuit simulations. This method is faster than direct optimization of original device and circuit models. Compared to existing polynomial or table look-up models used in analysis and optimization, the proposed approach has the capability to handle high-dimensional and highly nonlinear problems. >

PWM-switch modeling of DC-DC converters

Abstract: The introduced PWM-switch modeling method is a simple method for modeling pulse-width-modulated (PWM) DC-DC converters operating in the continuous conduction mode. The main advantage of this method is its versatility and simple implementation compared to other methods. The basic idea is the replacement of the switches in the converter by their time-averaged models. These switch models have been developed in such a way that the converter model provides the same results as the state-space-averaging technique but not including nonlinear effects. Simple rules for determination of the switch models are obtained. The resulting model is a time-averaged equivalent circuit model where all branch currents and node voltages correspond to their averaged values of the corresponding original currents and voltages. The model also includes parasitics, second-order effects and nonlinearities, and can be implemented in any circuit-oriented simulation tool. The same model is used for the simulation of the steady-state and the transient behavior. >

On the frequency limitations of the circuits based on second generation current conveyors

Abstract: An equivalent circuit for the translinear implementation of the second generation current conveyors with positive or negative current transfer is given. This circuit takes into account the various parasitic elements of the conveyor which induce frequency limitations (gain values, poles of the transfers, and parasitic impedances). The methods allowing the determination of the values for these parasitic elements are indicated and discussed. The effect of each element on the frequency responses of the circuits using the conveyors are studied in every detail. The frequency behavior of two circuits are analyzed as examples: a voltage amplifier without feedback and two configurations for a second order biquad filter operating in current-mode. All the theoretical results of the analysis are well confirmed from SPICE simulations.

Physical Interpretation of the Warburg Impedance

Abstract: The physical origin of the capacitive behavior of the Warburg impedance (ZW) and adsorption pseudocapacitance (Cϕ) is discussed. A simple derivation of ZW, based only on the Nernst diffusion layer thickness (δ = (πDt]1/2), is presented. An alternate equivalent circuit is proposed in which ZW is represented by a series combination of a resistor (the Warburg pseudoresistance [RW]) and a capacitor (the Warburg pseudocapacitance [CW]). The values of these new circuit elements are independent of potential. On the other hand, they are proportional to ω−1/2, leading to the so-called “constant phase element” that is observed experimentally. In contrast, the usual elements employed in equivalent circuit models to describe the voltage-current characteristics of the interphase (e.g., the faradaic resistance [RF], double-layer capacitance [Cdl], and adsorption pseudocapacitance [Cϕ]) are independent of frequency but may change with potential over many orders of magnitude. It is shown that the frequency depen...

Chua's circuit can be generated by CNN cells

Abstract: A new realization for the unfolded Chua's circuit is introduced. It has been derived from the connection of three simple generalized cellular neural network (CNN) cells. The main theoretical implication of this result is that the CNN cell represents the primitive for realizing high complex dynamics. The circuit implementation of the introduced system and experimental results referring to the double scroll attractor are reported. >

Analysis of self-excited induction generators using an iterative method

Abstract: This paper describes the steady-state analysis of self-excited induction generators (SEIG) using an iterative method. By considering the conductances connected across the air gap nodes, an iteration procedure is developed for the determination of the self-excited per-unit frequency, which enables the equivalent circuit to be completely solved. The proposed method involves only simple algebraic calculations, but the accuracy is good and convergence is rapid. The method is subsequently extended to include core loss effects and the analysis of SEIG with series capacitance compensation. Very good agreement between experimental and computed results has been obtained on a 2 kW laboratory machine. >

Signal processing delay circuit

Abstract: A signal processing delay circuit is fabricated as a semiconductor integration circuit to cope with increase in the data transfer speed and data recording and reproducing density on a recording medium. In the delay circuit, the amount of delay of a reference delay circuit of a delay PLL is controlled to take a fixed value independent of deviation in quality of the semiconductor circuit, change in power, and alteration in temperature. A control signal supervising the delay amount of the reference delay circuit is employed to control amounts of delay of input signals supplied to a window adjustment delay circuit of a window adjustment circuit and a T/2 generation delay circuit generating a synchronizing signal. Each of these delay circuits includes an analog variable delay circuit having the same configuration. The window adjustment delay circuit is supervised by a signal obtained by weighting the control signal by a D/A converter. A data acquisition circuit and a data write circuit each include an analog variable delay circuit.

An approach to determining an equivalent circuit for HEMTs

Abstract: A simple way to determine a small-signal equivalent circuit of High Electron Mobility Transistors (HEMTs) is proposed. Intrinsic elements determined by a conventional analytical parameter transformation technique are described as functions of extrinsic elements. Assuming that the equivalent circuit composed of lumped elements is valid over the whole frequency range of the measurements, the extrinsic elements are iteratively determined using the variance of the intrinsic elements as an optimization criterion. Measurements of S-parameters up to 62.5 GHz at more than 100 different bias points confirmed that the HEMT equivalent circuit is consistent for all bias points. >

Circuit designing apparatus of an interactive type

Abstract: A circuit designing apparatus of an interactive type which enables a simplified and high-speed circuit design process while largely reducing a burden on a designer, having a speed analyzing unit for conducting a delay computation for each wiring path on a circuit to be designed and a display control unit for displaying a result of the delay computation by the speed analyzing unit on a display unit. When the speed analyzing unit conducts a delay computation, a delay value of each logic component forming the circuit that is an object of the design is set and altered according to a dullness of a signal waveform inputted to the logic component. The circuit designing apparatus of an interactive type may be applied to a system for conducting a circuit design of an integrated circuit such as an LSI or the like or a printed circuit board.

Dynamic modelling of battery energy storage system and application to power system stability

Abstract: A useful and systematic dynamic model of a battery energy storage system (BES) is developed for a large-scale power system stability study. The model takes into account converter equivalent circuits, battery characteristics and internal losses. Both charging mode and discharging mode are presented. The model is expressed in equivalent transfer function blocks, and it can be easily used in dynamic stability analysis of a power system. To examine the dynamic behaviour of the model, applications to the damping of turbogenerator torsional oscillations are performed. Active and reactive power modulation by the BES can be controlled according to system requirements. Eigenvalue analysis and dynamic simulations are performed to demonstrate the damping effect of the BES.

Design of a traveling wave type ultrasonic motor

Abstract: The purpose of the present paper is to establish a method of design for a traveling wave type ultrasonic motor. This method is based on two models for the ultrasonic motor. A two-dimensional elastic contact model is used for estimating the friction drive between the rotor and vibrator of the motor. Moreover, an electrical equivalent circuit is used to estimate the interaction between the electrical and mechanical parts of the vibrator. The proposed method is applied to the design of a prototype motor. To determine applicability of the method, the load characteristics of the prototype motor are measured. The measured characteristics agree with the required ones which are specified in advance. As a result, the validity of the proposed method is experimentally confirmed. >

Method and apparatus for simulating a microelectronic interconnect circuit

Abstract: A method and apparatus for simulating a microelectronic circuit or system includes the storing of a microelectronic circuit or system representation in a computer and then transforming the representation into an equivalent DC circuit containing resistive, capacitive and inductive elements. Then, a directed graph of the DC equivalent circuit is generated and a spanning tree is constructed therefrom. The spanning tree is then actually or virtually traversed to obtain multiple generations of circuit moments. The moments are then used to calculate the poles and residues for a given node and generate an approximate model of the circuit's transient response at that node. Moment shifting is used to provide for a stable approximate model. The actual residues corresponding to the coefficients of the time domain representation for the model can be calculated using the first q-1 moments. This constitutes a partial-Pade approximation.

New design for QCM sensors in liquids

Abstract: The use of quartz-crystal microbalance (QCM) sensors in liquids for analytical purposes requires a well-designed transducer. Therefore a theoretical model is necessary to characterize the influence of liquid properties like density, viscosity, conductivity and dielectric behaviour. The high damping of the liquid loading results in a large loss of the quartz-crystal quality factor. Special electronics and a suitable sensor cell are necessary to obtain good frequency stability. The paper describes a new device based on an operational transconductance amplifier (OTA) with a very high bandwidth. Experimental results illustrate the ability of the sensor system to detect small amounts of special analytes in liquids.

Simplified three-phase transformer model for electromagnetic transient studies

Abstract: This paper presents a simplified high-frequency model for three-phase, twoand three-winding transformers. The model is based on the classical 60 Hz equivalent circuit, extended to high frequencies by the addition of the winding capacitances and the synthesis of the frequency-dependent short-circuit branch by an RLC equivalent network. By retaining the T-form of the classical model, it is possible to separate the frequency-dependent series branch from the constant-valued shunt capacitances. Since the short-circuit branch can be synthesized by a minimum-phase-shift rational approximation, the mathematical complications of fitting mutual impedance or admittance functions are avoided and the model is guaranteed to be numerically absolutely stable. Experimental tests were performed on actual power transformers to determine the parameters of the model. EMTP simulation results are also presented. >

Linear Circuit Analysis

Abstract: Lapice transfrom analysis- basics Laplace transfrom analysis - circuit applications Laplace transform analysis - transfer function applications time domain circuit response computations the convolution method resonant and bandpass circuits magnetically coupled circuits and transformers two-ports analysis of interconnected two-ports principles of basic filtering Fourier series with applications to electronic circuits. Appendices: introduction to magnetic circuit analysis SPICE for basic circuits.

Low-voltage transient bipolar effect induced by dynamic floating-body charging in PD/SOI MOSFETs

Abstract: Partially-depleted (PD) SOI MOSFETs offer improved threshold control and sensitivity over fully depleted devices, but the effects of dynamic floating-body charging on the threshold voltage VT(t) can possibly lead to instabilities in PD/SOI circuits. We show in this paper that the dynamic charging of the body can also induce a parasitic bipolar-transistor (BJT) transient current which can be significant even at low voltages well below the drain-source breakdown defined by the BJT. Our results indicate that if device/circuit design allows substantial variation of the body charge, then the transient BJT current could be large enough to upset the logic or memory (SRAM or DRAM) function of a chip. They further show that such an upset becomes more probable as the device is scaled, and they give insight regarding device and circuit design to reduce the probability.

A physical charge-based model for non-fully depleted SOI MOSFET's and its use in assessing floating-body effects in SOI CMOS circuits

Abstract: A new model for the non-fully depleted (NFD) SOI MOSFET is developed and used to study floating-body effects in SOI CMOS circuits. The charge-based model is physical, yet compact and thus suitable for device/circuit simulation. Verified by numerical device simulations and test-device measurements, and implemented in (SOI)SPICE, it reliably predicts floating-body effects resulting from free-carrier charging in the NFD/SOI MOSFET, including the purportedly beneficial supra-ideal sub-threshold slope due to impact ionization and a saturation current enhancement due to thermal generation. SOISPICE CMOS circuit simulations reveal that the former effect is not beneficial and could be detrimental, but the latter effect can be beneficial, especially in low-voltage applications, when accompanied by a dynamic floating-body effect that effectively reduces static power. The dynamic floating-body effects are hysteretic, however, and hence exploitation of the beneficial ones will necessitate device/circuit design scrutiny aided by physical models such as the one presented herein. >

Extraction of the InP/GaInAs heterojunction bipolar transistor small-signal equivalent circuit

Abstract: An extraction technique for determining the small-signal equivalent circuit model of an InP/GaInAs heterojunction bipolar transistor is presented. The equivalent circuit includes the extrinsic base collector capacitance and extrinsic base resistance. It is clearly indicated which elements are uniquely determined, and which elements are estimated. >

K-winners-take-all circuit with O(N) complexity

Abstract: Presents a k-winners-take-all circuit that is an extension of the winner-take-all circuit by Lazzaro et al. (1989). The problem of selecting the largest k numbers is formulated as a mathematical programming problem whose solution scheme, based on the Lagrange multiplier method, is directly implemented on an analog circuit. The wire length in this circuit grows only linearly with the number of elements, and the circuit is more suitable for real-time processing than the Hopfield networks because the present circuit produces the solution almost instantaneously-in contrast to the Hopfield network, which requires transient convergence to the solution from a precise initial state. The selection resolution in the present circuit is, however, only finite in contrast to the almost infinite resolution in the Hopfield networks. >

KHN-equivalent biquad using current conveyors

Abstract: A new current-conveyor-based (CC) biquad, equivalent to the well known KHN circuit, is introduced. The proposed circuit employs exactly the same number (five) of CCs and resistors (six/seven) along with two grounded capacitors as in the two CC biquads recently reported by Soliman. However, in contrast to Soliman's circuits, the proposed biquad offers several other advantages.

The Two Winding Transformer: an Experimental Method to Obtain a Wide Frequency Range Equivalent Circuit

Abstract: A lumped-component equivalent circuit has been developed by our team to model the electric behavior of any two-winding transformer. This circuit is general: its topology is independent of shape, sizes, and technology chosen. Changing the sample results only in a change of numerical values. Moreover, this circuit is suitable in a wide frequency range: from dc up to, at least, one decade beyond the maximum working frequency of the transformer. The aim of this paper is to present an experimental method which allows all the component values of this equivalent circuit to be determined, using only external impedance measurements. The method is illustrated by one example and, to conclude, Bode plots related to the circuit are compared to the experimental ones. >

Low-cost power factor correction circuit and method for electronic ballasts

Abstract: The present invention provides a low-cost power factor corrected electronic ballast circuit. A preferred embodiment includes a discontinuous conduction mode boost power factor correction circuit that is controlled with a simple pulse-width modulator (PWM) circuit comprising a few discrete components instead of an integrated circuit. The PWM circuit utilizes a reference waveform signal derived from the ballast inverter. The reference waveform is combined with a feedback signal to create a composite signal that is compared with a reference voltage to create a pulse-width-modulated signal. The feedback signal is used to regulate the bulk DC voltage. In an alternative embodiment, a feedforward signal that is proportional to the time-varying level of the rectified line voltage is added to the reference waveform and the feedback signal, and serves to modulate the pulse width of the boost circuit in a manner that reduces the harmonic distortion of the input current. In addition to the boost circuit, the power factor correction circuit can be realized with flyback and buck-boost topologies. The invention can also utilize several different types of inverter circuits.

On-line synchronous machine parameter estimation from small disturbance operating data

Abstract: This paper presents a step-by-step system identification approach to estimate the parameters of a three-phase salient-pole synchronous machine rated at 5 kVA from online small disturbance responses. The machine equivalent circuit model linear parameters and the nonlinear saturated parameters are estimated. The estimation is performed using the maximum likelihood algorithm. Simulation studies based on the online measured small and large dynamic disturbances are performed to validate the accuracy of the identified machine model including the saturation. >

Direct extraction of equivalent circuit parameters for heterojunction bipolar transistors

Abstract: A new method is presented for the direct extraction of hybrid-T equivalent circuits for heterojunction bipolar transistors. The method differs from previous ones by extracting the equivalent circuit without using test structures or numerical optimization techniques. Instead, all equivalent circuit parameters are calculated analytically from small-signal S-parameters measured under different bias conditions. The analysis includes the distributed nature of the HBT base. The calculated parameters are essentially frequency-independent and they exhibit systematic bias dependence over the typical operating range of the transistor. Thus, the present method ensures unique and physically meaningful parameters for transistor design improvement and large-signal circuit simulation. In addition, the present method is much faster than the numerical optimization method. >

Coplanar waveguide bandpass filter-a ribbon-of-brick-wall design

Abstract: This paper proposes a novel ribbon-of-brick-wall design of the coplanar waveguide bandpass filter which is built from cascading several sections of quarter wavelength open-end series stubs. The design originates from modeling the series stub as a system of two asymmetrically coupled transmission lines, which is then made equivalent to a basic filter element of admittance inverter. The relationship between the parameters of the coupled transmission lines and the admittance inverter is derived and the design charts are provided for the convenience of the designers. Systematic procedure is established to design the Chebyshev filter, which is also fabricated and measured. In addition, the quasistatic equivalent lumped circuit models of the discontinuities formed between two sections are evaluated and incorporated into the circuit simulation to get better prediction for the filter performance. The good agreement between simulation results and experimental data justifies the design procedure and validates the present analysis approach. >

Empirical modeling of low-frequency dispersive effects due to traps and thermal phenomena in III-V FET's

Abstract: The modeling of low-frequency dispersive effects due to surface state densities, deep level traps and thermal phenomena plays an important role in the large-signal performance prediction of III-V FET's. This paper describes an empirical modeling approach to accurately predict deviations between static and dynamic drain current characteristics caused by dispersive effects in III-V devices operating at microwave frequencies. It is based on reasonable assumptions and can easily be embedded in nonlinear FET models to be used in Harmonic-Balance tools for circuit analysis and design. Experimental and simulated results, for HEMT's and GaAs MESFET's of different manufacturers, that confirm the validity of the new approach, are presented and discussed together with the characterization procedures required.

Inductance calculations using partial inductances and macromodels

Abstract: Partial inductances as opposed to conventional loop inductances allow the decomposition of effects into their constituent parts. This leads to a complete analysis of complicated three dimensional structures. Coupling between parts of the structure is normally ignored in a conventional lumped circuit analysis. Macromodels of electric circuit substructures obtained from partial (inductance) equivalent circuit (PEEC) may be inserted into overall models and thereby contain more detailed effects than ordinary inductance models. We also show that the coupling is greatly reduced for some structures like transmission lines with differential mode currents.