Showing papers on "Equivalent circuit published in 1990"

Design of a simple high-power-factor rectifier based on the flyback converter

Abstract: An equivalent circuit model for the discontinuous conduction mode flyback converter based on the loss-free resistor concept is presented. This simple model correctly describes the basic power processing properties of the converter, including input port resistor emulation, output port power source characteristics, and control characteristics. Based on this model, steady-state design equations are described and are used in a design example. Design of the slow output voltage feedback loop is also considered. A small-signal AC model is developed for both the resistive load and the DC-DC converter-voltage regulator load cases. In addition, a simple first-order approximation for the line current distortion and phase shift caused by 120 Hz duty cycle variations is derived. >

Microwave circuit design using linear and nonlinear techniques

Abstract: Foreword by David Leeson. Preface. 1. RF/Microwave Systems. 2. Lumped and Distributed Elements. 3. Active Devices. 4. Two-Port Networks. 5. Impedance Matching. 6. Microwave Filters. 7. Noise in Linear Two-Ports. 8. Small- and Large-Signal Amplifier Design. 9. Power Amplifier Design. 10. Oscillator Design. 11. Microwave Mixer Design. 12. RF Switches and Attenuators. 13. Microwave Computer-Aided Workstations foor MMIC Requirements. Appendix A: BIP: Gummel-Poon Bipolar Transistor Model. Appendix B: Level 3 MOSFET. Appendix C: Noise Parameters of GaAs MESFETs. Appendix D: Derivations for Unilateral Gain Section. Appendix E: Vector Representation of Two-Tone Intermodulation Products. Appendix F: Passive Microwave Elements. Index.

Broad-band determination of the FET small-signal equivalent circuit

Abstract: A method to determine the broadband small-signal equivalent circuit of field-effect transistors (FETs) is proposed. This method is based on an analytic solution of the equations for the Y parameters of the intrinsic device and allows direct determination of the circuit elements at any specific frequency or averaged over a frequency range. The validity of the equivalent circuit can be verified by showing the frequency independence of each element. The method can be used for the whole range of measurement frequencies and can be applied to devices exhibiting severe low-frequency effects. >

Canonical realization of Chua's circuit family

Abstract: A new canonical piecewise-linear circuit capable of realizing every member of the Chua's circuit family is presented. It contains only six two-terminal elements: five of them are linear resistors, capacitors, and inductors, and only one element is a three-segment piecewise-linear resistor. It is canonical in the sense that (1) it can exhibit all possible phenomena associated with any three-region symmetric piecewise-linear continuous vector fields and (2) it contains the minimum number of circuit elements needed for such a circuit. This circuit is used to prove a theorem that specifies the constraint on the types of eigenvalue patterns associated with a piecewise-linear continuous vector field having three equilibrium points. This theorem has an explicit physical meaning and unifies the corresponding theorem in the work of L.O. Chua et al. (1986) and C.P. Silva and L.O. Chua et al. (1988). Also presented are some computer simulation results for this circuit, including some new attractors that have not been observed before. >

Transformers as equivalent circuits for switches: general proofs and D-Q transformation-based analyses

Abstract: The equivalent circuits for the switches in DC-DC, DC-AC, AC-DC, and AC-AC converters are proved to be time-varying transformers. This result is used in the analyses of DC-DC converters, an eight-order current source rectifier-inverter, and a buck-boost inverter. The circuit D-Q transformation is proposed for the analyses of the AC converters such as inverters, rectifiers, and cycloconverters which include the time-varying transformers. Gyrators appear in the D-Q transformed inductors and capacitors of the AC converters. Few equational manipulations are required to determine the steady-state operating points and the small signal gains of the converters. The analysis result for the rectifier-inverter shows that the circuit has self-short-circuit protection capability and strong immunity in the parasitic inductor resistance. >

Modeling and simulation of interconnection delays and crosstalks in high-speed integrated circuits

Abstract: A computer model for n parallel microstrip lines is developed for circuit simulation. This model for the lossy transmission line system can be readily implemented into circuit simulators and can accurately simulate the delay and crosstalk effects of interconnects in high-speed integrated circuits. Modal analysis is applied to decouple the n-coupled-line system into n independent lines, and the characteristic solutions of telegraph equations are represented by a set of simple time-varying equivalent circuits. The model has been implemented in a general-purpose circuit simulator, iSMILE, which is compatible with SPICE. Simulation results on propagation delay times and crosstalk are presented for high-speed GaAs HEMT (high-electron-mobility transistor) integrated circuits. >

Frequency-dependent electrical characteristics of GaAs MESFETs

Abstract: Output resistance and transconductance of GaAs MESFETs have been observed to change significantly at very low frequencies. Extensive measurements of these characteristics as a function of device bias are reported. Direct measurements of the dispersive behavior between DC and 100 kHz and over a broad temperature range have been made on ion-implanted monolithic microwave IC (MMIC) devices. Conductance deep level transient spectroscopy (DLTS) and microwave S-parameter measurements have also been made to investigate this behavior. These measurements reveal that surface or channel-substrate interface traps in the material are most likely to be responsible for the observed behavior. A new equivalent-circuit model which accounts for many of the observed characteristics is developed. Unlike previously proposed equivalent circuits, the model does not rely on physically unrealistic circuit element values in order to obtain accurate performance predictions. The bias dependence of circuit element values is computed for one device. Effects not described by the model are also discussed. >

Equivalent capacitances of coplanar waveguide discontinuities and interdigitated capacitors using a three-dimensional finite difference method

Abstract: Equivalent capacitances of coplanar waveguide discontinuities on multilayered substrates are calculated using a three-dimensional finite-different method. The application of the method is demonstrated for open ends and gaps in microstrip and coplanar waveguides, as well as for more complicated structures such as interdigitated capacitors. The main advantage of the method is its flexibility in treating multilayered substrates and different conductor configurations. It can therefore be applied to more complicated structures such as interdigitated capacitors, air bridges, and waveguide transitions. The effect of conductor metallization thickness and shielding walls is also taken into account. Good agreement between the calculated data and measurements up to 25 GHz in the case of coplanar structures indicates the validity of the static analysis even for high frequencies. >

Characterization of MIS structure coplanar transmission lines for investigation of signal propagation in integrated circuits

Abstract: A full-wave analysis of metal-insulator-semiconductor (MIS) structure micron coplanar transmission lines on doped semiconductor substrates is carried out using a finite-difference time-domain approach. Metal conductor loss is taken into account in the analysis. Line parameters and electromagnetic field distributions are calculated over a wide frequency range involving slow-wave and dielectric quasi-transverse-electromagnetic mode limits. Measurements of these line parameters, varying substrate resistivity from 1 to 1000 Omega -cm, in the frequency range up to 40 GHz are also presented, and these agree with the analysis quite well. On the basis of these results, an equivalent circuit line model is induced and some considerations on the relationship between line structure and properties made. >

Powers in nonsinusoidal networks: their interpretation, analysis, and measurement

Abstract: A nonlinear or periodically time-variant load sometimes has to be considered not as the receiver, but as the source of energy, at least for some harmonic frequencies. This can be explained in terms of its equivalent circuit, usually composed of passive elements and harmonic sources which make the power phenomena in such a circuit much more complex than in a linear circuit. The necessity of comprehension of these phenomena stems from the fact that they determine the efficiency of the power transmission and the possibility of power factor improvement. They also affect the energy accounts. A method is suggested for the apparent power decomposition into components related to current components of distinctively different physical interpretation. A digital analyzer for measuring these powers is described. >

Inductive power transfer to an electric vehicle-analytical model

Abstract: The roadway powered electric vehicle (RPEV) system is a unique electric vehicle system that receives electric power by inductive coupling from an inductor buried beneath the road surface. The analytical model of the system that transfers power from the wayside to the vehicle battery and DC traction motor is analyzed. This model includes the roadway inductor, the vehicle-mounted pick up inductor, and the onboard circuitry for control/conditioning of the coupled power. The equivalent circuit model of the inductive power coupling system is derived. Based on this model, the electrical characteristics of the system are explained. Trade-offs in selecting system parameters are discussed. All test results have tended to confirm simulation results obtained using the analytical model. >

A theory of a quartz crystal microbalance based upon a Mason equivalent circuit

Abstract: The authors analyzed the behavior of a quartz crystal microbalance (QCM) in the experimental environments of air and liquid using a Mason equivalent circuit. It was found that the mass loading effect of QCM could be regarded as an inductance increase, and the analytical equation of the frequency shift, which is valid over the wide range of the thickness of a loading film, was derived. Utilizing this equation, the frequency shift can be predicted without solving the transcendental equation. Furthermore, it was found that various kinds of QCM problems, such as liquid loading and mass loading in liquid, could be solved using the same method because the acoustic load was expressed as a circuit component. Finally, the method to enhance mass loading sensitivity by depositing a thick film with low acoustic impedance over the quartz plate, was suggested.

Power and stability limitations of resonant tunneling diodes

Abstract: Stability criteria for resonant tunneling diodes are investigated. Details of how extrinsic elements, such as series inductance and parallel capacitance, affect the stability are presented. A GaAs/AlAs/InGaAs/AlAs/GaAs double-barrier diode is investigated, showing the effect of different modes of low-frequency oscillation and the extrinsic circuit required for stabilization. The effect of device stabilization on high-frequency power generation is described. The main conclusions of the paper are: (1) stable resonant tunneling diode operation is difficult to obtain, and (2) the circuit and device conditions required for stable operation greatly reduce the amount of power that can be produced by these devices. >

Realization of loss-free resistive elements

Abstract: The realization of loss-free elements with resistive I-V characteristics is presented. The realization is achieved by controlling the parameters of loss-free two-ports that have a transformer or gyrator matrix. The power absorbed by the element is transferred to the source, so that, in principle, no losses occur. The use of such elements is expected to be of importance in power electronics, power conversion systems, gas discharge devices, control systems, robotics, and microwave circuits. Such an element was realized using a switched-mode circuit technique. It was applied to the stabilization of a gas laser system. The circuit replaced a conventional resistor that dissipated power up to 40 W. The replacement circuit dissipated only 10 W (equivalent to a conversion efficiency of 75%). >

Performance characteristics and optimum utilization of a cage machine as capacitance excited induction generator

Abstract: The performance characteristics of a cage induction machine operating as a self-excited induction generator (SEIG) in stand-alone mode are presented. A static capacitor bank is considered to self-excite the machine and to maintain its terminal voltage constant. The lagging reactive power requirement of self-excited induction generator is obtained for different load values. The effect of speed on the excitation requirement of the cage machine has also been studied. An algorithm is developed to achieve these characteristics using the Newton-Raphson method and a steady-state equivalent circuit of the machine. The developed analytical technique is extended to evaluate the number of steps of switching capacitors for loading the machine up to its full load rating while maintaining the terminal voltage within desired limits. The selection of an optimum terminal voltage corresponding to the maximum output of the machine for its optimum utilization is also made using single-variable optimization. >

Understanding wide-band MOS transistors

Abstract: A quantitative understanding of MOS-transistor speed has been slow to emerge because of the absence of a commonly agreed-upon figure of merit for MOS-transistor speed and a lack of familiarity among designers with MOS-amplifier topologies. It is suggested that these problems can be addressed through the use of the unity-gain current frequency (f/sub T/) as a figure of merit for MOS transistors, the use of f/sub T/ in the prediction of amplifier bandwidth, and a wider familiarity among designers with practical examples of MOS wideband amplifiers. The use of f/sub T/ as a figure of merit is discussed, and the achievable amplifier bandwidths are determined. Increasing the f/sub T/ of an MOS device by making the g/sub m/ larger or the C/sub g/ smaller, or both, is discussed. Wideband CMOS amplifiers are considered. >

Synthesis of averaged circuit models for switched power converters

Abstract: Averaged circuit models for switching converters are developed using a direct circuit averaging method. The method proceeds in a systematic fashion by determining appropriate averaged circuit elements that are consistent with the averaged circuit waveforms. The averaged circuit models that are obtained are synthesis of the state-space averaged models for the underlying switched circuits. An important feature of the method is that it is applicable to switched circuits whose nonswitch elements may be nonlinear. The results obtained using this method are compared with the results on averaged circuit models available in the literature. >

An equivalent circuit approach to analysis of synchronous machines with saliency and saturation

Abstract: An equivalent circuit approach is presented for synchronous machine analysis. The approach provides a detailed treatment of magnetic nonlinearity without excessive computational complexity. The number of parameters is typically in the range of 30 to 100, in contrast with 13 to 19 in conventional linear models and with 2000 to 10000 for finite-element analysis. The models developed are intended for use with digital simulation software in the solution of transient, asynchronous, and synchronous steady-state situations. >

A finite-difference transmission line matrix method incorporating a nonlinear device model

Abstract: A variable-mesh combination of the expanded-node transmission line matrix (TLM) and finite-difference-time-domain (FD-TD) methods for solving time-domain electromagnetic problems is described. It retains the physical process of wave propagation and the numerical stability of the former and it has the computational efficiency of the latter. This full-wave finite-difference transmission line matrix (FD-TLM) method utilizes transmission lines of differing impedances to implement a three-dimensional variable mesh, which makes practical the simulation of structures having fine details, such as digital integrated circuits (ICs). Circuit models for lumped resistors, capacitors, diodes, and MESFETs have been developed and included for use in simulating digital and microwave ICs. The validity of the variable mesh implementation is verified by comparing an FD-TLM simulation of a picosecond pulse generator structure with electrooptical measurements, and the validity of the device model implementation is verified by comparing an FD-TLM simulation of a MESFET logic inverter with a SPICE simulation. >

High-frequency operation of a planar-type microtransformer and its application to multilayered switching regulators

Abstract: The operation of a multilayered microtransformer composed of planar zig-zag coils and amorphous magnetic film is described. The transformer has a maximum efficiency of 77.5%. Its equivalent circuit is approximated by the parallel connection of the winding inductance and of the stray capacitance. Variable magnetic coupling is obtained between the primary and secondary windings by shifting the relative position of the two coils. The microtransformer is used in a magnetically controlled multilayered switching regulator. The regulator has an output of 1.4 W and an efficiency of 24%. The magnetization loss in the circuit is the same as that of the semiconductors. A two-output-type multilayered switching regulator is also proposed that has an acceptably good output characteristic at each port even though a common magnetic film is used. >

A Study of Pyrite/Solution Interface by Impedance Spectroscopy

Abstract: Several equivalent circuit models are considered for analysis of the ac impedance spectrum of pyrite/solution interface. These models take into account the presence of coating layers and the contributions from surface roughness and diffusion. In this paper an optimization procedure is described to estimate the parameters of the equivalent circuit, namely, the value of various resistors, capacitors, etc. The procedure can also be used to identify the equivalent circuit which best describes the measured impedance spectrum. The impedance results of a pyrite electrode in sodium carbonate and borate solutions are analyzed in terms of the parameters of the equivalent circuit which best describe the spectra obtained under several conditions. Such an analysis was used to distinguish the type of electrode processes which control oxidation behavior of pyrite.

A simple scheme for unity power-factor rectification for high frequency AC buses

Abstract: A simple scheme is proposed for offline unity power factor rectification for high-frequency AC buses (20 kHz). A bandpass filter of the series-resonant type, centered at the line frequency, is inserted between the line and the full-wave rectified load. The Q=Z/sub 0//R/sub L/ formed by the load and the characteristic impedance of the tank circuit determines the power factor, the boundary between continuous and discontinuous conduction modes, the peak stresses, and the transient response of the rectifier. It is shown that for Q>2/ pi the rectifier operates in continuous conduction mode and the output voltage is independent of the load. Also, it is shown that for Q>2 the line current is nearly sinusoidal with less than 5% third-harmonic distortion and the power factor is essentially unity. An increase in Q causes an increase in the peak voltages of the tank circuit and a slower transient response of the rectifier circuit. The DC, small-signal, and transient analyses of the rectifier circuit are carried out, and the results are in good agreement with simulation and experimental results. >

Neural network processing system using semiconductor memories

Abstract: Herein disclosed is a data processing system having a memory packaged therein for realizing a large-scale and high-speed parallel distributed processing and, especially, a data processing system for the neural network processing. The neural network processing system according to the present invention comprises: a memory circuit for storing neuron output values, connection weights, the desired values of outputs, and data necessary for learning; an input/output circuit for writing or reading data in or out of said memory circuit; a processing circuit for performing a processing for determining the neuron outputs such as the product, sum and nonlinear conversion of the data stored in said memory circuit, a comparison of the output value and its desired value, and a processing necessary for learning; and a control circuit for controlling the operations of said memory circuit, said input/output circuit and said processing circuit. The processing circuit is constructed to include at least one of an adder, a multiplier, a nonlinear transfer function circuit and a comparator so that at least a portion of the processing necessary for determining the neutron output values such as the product or sum may be accomplished in parallel. Moreover, these circuits are shared among a plurality of neutrons and are operated in a time sharing manner to determine the plural neuron output values. Still moreover, the aforementioned comparator compares the neuron output value determined and the desired value of the output in parallel.

Bar-grid oscillators

Abstract: Grid oscillators are an attractive way of obtaining high power levels from the solid-state devices, since potentially the output powers of thousands of individual devices can be combined. The active devices do not require an external locking signal, and the power combining is done in free space. Thirty-six transistors were mounted on parallel brass bars, which provide a stable bias and have a low thermal resistance. The output power degraded gradually when the devices failed. The grid gave an effective radiated power of 3 W at 3 GHz. The directivity was 11.3 dB, and the DC-to-RF efficiency was 22%. Modulation capabilities of the grid were demonstrated. An equivalent circuit model for the grid is derived, and comparison with experimental results is shown. >

Charge injection logic

Abstract: The charge injection transistor is a semiconductor device based on transfer of hot electrons between separately contacted conducting layers. The nature of hot‐electron injection by the real‐space transfer allows the implementation of novel circuit elements. In particular, we propose a multiterminal single‐device structure that works as a functional element with three logic inputs Xj (j=1,2,3) and one output equal to (X1∩X2∩X3)∪(X1∩X2∩X3). This device, called the norand, can perform both as a nor(X1,X2) and as an and(X1,X2) element, reprogrammable electrically by changing the X3 input. The operation of norand with logic gain is demonstrated experimentally by an equivalent circuit connection of discrete charge injection transistors implemented within InGaAs/InAlAs on InP technology.

Vector Circuit Theory for Isotropic and Chiral Slabs

Abstract: This paper discusses modelling of isotropic and chiral slabs by using vector circuits involving dyadic impedances and admittances and tangential field components. The analysis is based on the exact averaging method for the Fourier-transformed field equations of the slab. Then, by considering tangential electric and magnetic fields as voltages and currents, analogous vector circuits, such as equivalent two-port circuits, Thevenin and Norton circuits and T and II circuits, are given for isotropic and chiral isotropic and homogeneous and nonhomogeneous slabs. These vector circuits are most appropriate when calculating propagated and reflected fields for general excitation. In addition, different approximations related to slabs thin either in wavenumbers in the normal or in transversal directions or to slabs with different propagation constant ratios are considered. A case when a slab can be simulated by a sheet is also discussed. The results obtained can be useful in many practical situations, for example, f...

Electromagnetic and transport considerations in subpicosecond photoconductive switch modeling

Abstract: The authors discuss a combination of direct finite-difference time-domain solutions of Maxwell's equations and Monte Carlo models of photocarrier transport used to avoid assumptions commonly made in developing equivalent circuit models for transmission lines and in other simplifications commonly made in modeling conductivity. Problems that complicate the development of an accurate model for subpicosecond optoelectronic switching and the measurement of electrical waveforms on microstrip lines are discussed. >