Showing papers on "Equivalent circuit published in 1978"

Modelling, analyses and design of switching converters

Abstract: A state-space averaging method for modelling switching dc-to-dc converters for both continuous and discontinuous conduction mode is developed. In each case the starting point is the unified state-space representation, and the end result is a complete linear circuit model, for each conduction mode, which correctly represents all essential features, namely, the input, output, and transfer properties (static dc as well as dynamic ac small-signal). While the method is generally applicable to any switching converter, it is extensively illustrated for the three common power stages (buck, boost, and buck-boost). The results for these converters are then easily tabulated owing to the fixed equivalent circuit topology of their canonical circuit model. The insights that emerge from the general state-space modelling approach lead to the design of new converter topologies through the study of generic properties of the cascade connection of basic buck and boost converters.

Experimental Study of Symmetric Microstrip Bends and Their Compensation

Abstract: An experimental study of microstrip bends is described. For right-angle corners, equivalent circuit parameters covering a wide range of frequencies, linewidths, and permittivities are presented and compared with the limited theoretical values available. The influence of mitering or rounding of the corner was investigated, and useful empirical expressions are given for the optimum miter.

Bilayer Lipid Membranes

Abstract: Thin lipid membranes formed across an aperture in a teflon foil are frequently used as model systems to simulate the hydrophobic diffusion barrier of biological membranes. These membranes have a thickness of about twice the length of a lipid molecule (bilayer membranes) and are prepared either by a spontaneous transition of a thick lamella made from a solution of lipids in a hydrocarbon [1] or by a direct “addition” of two monomolecular lipid layers on the two water surfaces separated by the teflon foil [2]. The aqueous phases on both sides of these planar membranes are easily accessible by electrodes which may serve to study the electrical properties of the membranes. The whole system allows the application of steady state electrical methods as well as that of fast relaxation methods. The latter include the voltage jump-current relaxation technique [3,6], the charge pulse method [4,5] as well as the temperature jump method [6]. These kinetic techniques have been used throughout recent years to investigate ion transport phenomena across bilayer lipid membranes. Unmodified lipid membranes have been found to represent high energy barriers for the movement of inorganic cations and anions. A simple equivalent electrical circuit of the membrane consists of a parallel arrangement of the membrane resistance RM and the membrane capacitance CM (typical values: RM = 106-108μcm2, CM = 0.3-0.8μF/cm2). A refined version composed of three of such elements (one for the hydrocarbonlike membrane interior, the two others for the polar membrane-water interfaces) has been suggested on the basis of a.c. measurements [7]. These measurements were, however, confined to the rather small band width of 0.1-100 Hz. A different possibility of testing such a circuit is to make use of the voltage jump method. The induced current relaxation may be measured with a time resolution of at least 1 μs and very high sensitivity by using signal averaging techniques. For the three element circuit described above the relaxation should consist of two exponential terms. At least five different relaxation times were, however, necessary to obtain a sufficiently good fit to the experimental data [8.9]. This finding indicates that even the refined equivalent circuit is insufficient for a phenomenological description of the high frequency behaviour of bilayer lipid membranes. The complex current relaxation may be interpreted on the basis of cooperative dielectric relaxation phenomena associated with the dipoles of the polar head groups of the lipid molecules.

A Highly Stabilized Low-Noise GaAs FET Integrated Oscillator with a Dielectric Resonator in the C Band

Abstract: A GaAs FET integrated oscillator stabilized with a BaO--TiO/sub 2/ system ceramic dielectric resonator provides a high-frequency-stabilized low-noise compact microwave power source. The newly developed ceramic has an expansion coefficient and dielectric constant temperature coefficient that offset each other and result in a small resonant frequency temperature coefficient. A stabilized oscillator output of 100 mW with a 17-percent efficiency and a frequency temperature coefficient as low as 2.3 ppm//spl deg/C are obtained at 6 GHz. FM noise level is reduced more the 30 dB by the stabilization. The dynamic properties of the oscillator and resonator are precisely measured to determine equivalent circuit representations. A large-signal design theory based on these equivalent circuit representations is presented to realize the optimal coupling condition between the oscillator and stabilizing resonator. The stabilized oscillator performance is sufficient for application to microwave communications systems.

Basic Electric Circuit Analysis

Abstract: 1. Introduction. 2. Resistive Circuits. 3. Dependent Sources and OP AMPS. 4. Analysis Methods. 5. Energy-Storage Elements. 6. First-Order Circuits. 7. Second-Order Circuits. 8. Sinusoidal Sources and Phasors. 9. AC Steady-State Analysis. 10. AC Steady-State Power. 11. Three-Phase Circuits. 12. The Laplace Transform. 13. Circuit Analysis in the s-DOMAIN. 14. Frequency Response. 15. Mutual Inductance and Two-Port Circuits. 16. Fourier Series and Transform. Appendix A: Matrix Methods. Appendix B: Complex Numbers and the Complex Exponential. Appendix C: Circuit Topology. Appendix D: Spice reference Guides. Appendix E: Answers to Selected Odd-Numbered Problems. Index.

Conversion Loss and Noise of Microwave and Millimeterwave Mixers: Part 2--Experiment

Abstract: The theory of noise and conversion loss in millimeter-wave mixers, developed in a companion paper, is applied to an 80-120-GHz mixer. Good agreement is obtained between theoretical and experimental results, and the source of the recently reported "anomalous noise" is explained. Experimental methods are described for measuring the embedding impedance and diode equivalent circuit, needed for the computer analysis.

Capacitance Parameters of Discontinuities in Microstriplines

Abstract: Capacitance components of microstrip equivalent circuit discontinuities of gaps and the T junctions have heen calculated using the quasi-static formulation. Comparison of the calculated results with experimental measurements where available show good agreement. The range of data extends that data previously published, and new results on parallel gaps also are included.

Tri-state type driver circuit

Abstract: This invention relates to a tri-state type driver circuit in which any one of the three possible output signals of "float", "on", or "off" is produced at high speed even when an output terminal is accompanied with a great load. The tri-state type driver circuit comprises an output inverter circuit which employs a bipolar transistor as a load thereof and a MOS-FET as a driver thereof, a first logical circuit which is coupled to an input terminal of the bipolar transistor, which first logical circuit is made up of a C-MOS circuit receiving an external select signal and a C-MOS circuit having an input signal transmitted thereto and whose output can be specified by the external select signal, and a second logical circuit which is coupled to an input terminal of the MOS-FET, which second logical circuit is made up of a C-MOS circuit receiving the external select signal and a C-MOS circuit having the input signal transmitted thereto. The state of the external select signal will determine whether the driver circuit output will be "float" (regardless of the input to the driver circuit) or "on" or "off" (in correspondence with the input to the driver circuit).

Static characteristics of Josephson interferometers

Abstract: This investigation deals with the range in operating currents for which a Josephson interferometer, sometimes also referred to as Superconducting QUantum Interference Device (SQUID), may remain in the zero-voltage Josephson condition. An interferometer consists of one or more inductive loops each of which contains two Josephson junctions or other weak links. Two types of current are considered. Gate currentIgpasses the junctions in parallel. Control currentIcgenerates magnetic flux via inductive coupling in the loops. Zero-voltage operation is possible within certain areas of theIg,Icplane. These areas are manifestations of flux-quantum states and their boundary lines are referred to as static characteristics. In view of the nonlinearity of the constituting equations, not all their formal solutions are physically realizable. A stability analysis yields criteria which permit the identification of realizable operating conditions. The static characteristics comprise operating conditions where the limit of stability is reached. To obtain the static characteristics, linearized equations may be utilized if theLIo product, a measure for the size of an interferometer, is large compared to the flux quantumΦ0, whereL is the inductance per loop, andIo the maximum Josephson current per junction. As a general method of solving system of transcendental equations, continuation is discussed. The utilization of continuation for obtaining interferometer characteristics is explained. It is shown that some changes in the gate-current feed arrangement are equivalent to shearing the characteristics in theIg,Icplane. Analytical results are given on extrema, inflexion points, and singularities in the shape of cusps which conceptually relate to the existence and connectivity of flux-quantum states. Experimental static characteristics are presented on two-and four-junction interferometers. They are in agreement with characteristics computed on the basis of simple lumped circuit models. Relevant circuit parameters are obtained from the experimental characteristics.

Coupling of Waveguides through Large Apertures

Abstract: A closed form expression for the equivalent network of a narrow transverse slot in the common broadwall between two waveguides is derived in terms of self-reaction and discontinuity in modal voltage. The coupling is expressed in terms of equivalent circuit parameter. A comparison between theoretical results with those obtained from the results of Levinson and Fredberg (for slot length > 0.4a, where a is the broad dimension of the waveguide), the results obtained from the formula of Sangster and the experimental results are presented.

Ford-girling equivalent circuit using c.c.II

Abstract: A new configuration equivalent to the well known Ford-Girling circuit and using c.c.II instead of the o.a. is given. Applications and advantages of the new realisation are discussed.

Practical Modeling of the Circuit Breaker ARC as a Short Line Fault Interrupter

Abstract: The short-line fault interrupting ability of gas-blast circuit breakers is limited by arc energy balance processes very close to current zero. Practical calculation of the energy balance limit in a given circuit requires mathematical modeling of the arc as a circuit element. Using the combined Cassie-Mayr model, useful relations are derived for treating the limiting cases of the short-line fault both with and without capacitance shunting. Included are methods for approximate analysis and extrapolation of data from actual and simulated short-line fault tests with and without RRRV controlling resistance and capacitance shunts. In these analyses the arc is described by only two model parameters: a near-current-zero arc voltage Eo and an arc time constant 0, both definable as simple functions of the circuit di/dt. Examples are given of such analyses of high di/dt interrupting tests on actual and model SF6-blast interrupters.

Power up circuit with high noise immunity

Abstract: A power up circuit for an associated digital circuit is disclosed which prevents noise from falsely resetting the associated digital circuit after completion of the powering up function. The power up circuit has a series connection of a first capacitor and a high impedance coupled between the power supply and ground. The high impedance is connected in parallel with the source and drain electrodes of an enhancement type field effect transistor. The node of the high impedance and the first capacitor is connected to an inverting amplifier which produces an inverted output after the input signal falls to a threshold potential. The output of the inverting amplifier is connected to the gate of the field effect transistor and to a second capacitor which is connected to ground. The output of the inverting amplifier is applied to the reset line of the associated digital circuit to cause resetting of the digital circuit upon the connection of the power supply to the digital circuit. After powering up, the field effect transistor is biased on by the output of the inverting amplifier. Any noise pulses which are coupled to the first capacitor are shunted to ground by the low impedance of the turned on field effect transistor.

Dynamic depletion mode: an E/D MOSFET circuit method for improved performance

Abstract: A new method of designing enhancement/depletion (E/D) MOSFET circuits, involving the dynamic or pulsed use of depletion-mode devices, is described. The method can result in improvements in performance and/or power in the design of memory, logic, and driver circuits. The method is compared with the standard approach to the design of E/D circuits. Several circuits designed by the method have been simulated by use of a numerical circuit analysis program and have been placed on an experimental test chip. Theoretical and experimental results are presented.

Frequency characteristics of opto-acoustic transducers

Abstract: An opto-acoustic transducer (OAT) converts a spatial distribution of optical intensity into a corresponding distribution of acoustical amplitude. In designing such a device, operating frequency and bandwidth must be considered. We have developed an equivalent circuit model for the OAT to predict the frequency dependence of the transducing characteristics. In particular, the switching ratio, i.e., the ratio of acoustical pressurein the illuminated region to that in the dark region, and the transfer function for acoustical pressure-to-voltage amplitude are explored as functions of frequency. The switching ratios found to be extremely frequency sensitive for many important cases. The effects of this sensitivity on device design and performance are discussed.

A Useful Equivalence for a Coaxial-Waveguide Junction

Abstract: The junction formed by a coaxial line entering the broad wall of a rectangular waveguide is commonly used, but has not been accurately analyzed due to the electromagnetic-field complexity. An excellent correlation has been established between this complex structure and a similar one which has already been thoroughly characterized. This close correlation permits use of the equivalent circuit of the previously characterized structure as a representation for the coax-waveguide junction as well. This usage is made possible by study of the relationship which exists between the two configurations, thus allowing accurate circuit analysis of components utilizing the coax-waveguide junction.

Radiation Effects on GaAs MESFETs

Abstract: The effect of fast neutron and gamma radiation on the electrical characteristics of commercial 1 ?m and 4 ?m low noise GaAs MESFET has been evaluated. The change in the microwave scattering parameters at 2 to 4 GHz (S-band), 1 MHz equivalent circuit parameters, DC characteristics and low frequency input noise equivalent voltage from 2 KHz to 1.5 MHz was determined at neutron fluences between 5 × 1013 to 8 × 1014 n/cm2 and gamma doses of up to 8 × 107 rads (Si). These radiation induced changes are described and causes for these changes are discussed.

Polarity-and-load independent circuit arrangement for converting electrical energy

Abstract: A circuit arrangement for converting electrical energy has a static frequency converter which operates with a considerably higher frequency than the frequency to be produced, the arrangement has a heavy-duty switch, a transmitter and a rectifier on the secondary side, and a master control circuit, a regulating circuit and an auxiliary static frequency converter. The heavy-duty switches on the primary side and on the secondary side are provided for the two current directions with one transformer winding of a common transformer, and are also provided with filter sections for the low frequency range and high frequency range auxiliary frequency converters. The arrangement also is provided with quadrant shift locks at the primary side and the secondary side which determine the mode of operation of the static frequency converter in conjunction with the master circuit and the regulating circuit, whereby the output flow direction can be selected or is determined by a monitoring circuit.

A nonlinear circuit model for IMPATT diodes

Abstract: An improved nonlinear circuit model for IMPATT diodes is presented for which each element bears a simple relationship with the physical operating mechanisms inside the device. The model contains lumped nonlinear elements as well as lumped and distributed linear elements. In its most general form it incorporates various second-order effects heretofore neglected in other circuit models. These include the effects due to unequal hole and electron ionization rates, unequal hole and electron drift velocities, and carrier diffusion.

Hall-effect integrated circuit switch

Abstract: An integrated circuit in which the Hall-Effect device and the sensing circuit can be incorporated on a single monolithic chip includes a Hall-Effect generator responsive to a magnetic flux change for generating a Hall-Effect voltage. A differential amplifier and current mirror circuit are coupled to the Hall-Effect device in order to vary or track the threshold voltage of the differential amplifier circuit in accordance with the output voltage from the Hall-Effect device irrespective of current changes in the Hall-Effect device due to temperature variations.

Buried-Heterostructure Laser Packaging for Wideband Optical Transmission Systems

Abstract: The design and performances of packaged buried-heterostructure lasers (BH Lasers) are discussed. High laser-to-fiber coupling efficiencies of more than 50% are attained by a simple end-butt coupling scheme of using taper-ended graded-index optical fibers. In addition, modulation bandwidths of more than 1 GHz are realized through the reduction of parasitics due to the packaging. The equivalent circuit of the packaged device as well as the temperature dependence of the threshold current is also clarified to aid in the design of optical transmitter circuits.

Discontinuous inductor current in the optimum topology switching converter

Abstract: It is demonstrated, first, how the complex modular converter structures (such as cascade og the boost and buck converters) can be easily modelled in the discontinuous current mode by use of the state-space averaging method and equivalent circuit apptoach and by taking adavntage of the known properties and circuit models of the individual converter modules (boost and buck converters). Then, the recently introduced new optimum topology switching dc-to-dc converter is analyzed in the discontinuous inductor current mode. Unlike other converters with two inductors (such as casaded boost-buck), the new converter has a unique feature that both inductor currents become discontinuous at the same instant, and remain so with the same second (decay) interval. Moreover, for the first time, the discontinuity of the inductor current takes place at a nonzero inductor current level, with dc curreny, passing through both inductors in the remaining third part of the switching period. It is shown howthis peculiar behaviour can be successfully modelled and a simple analytic criterion for determination of the boundary between the continuous and discontinuous inductor current mode is obtained.

Dynamic ARC Analysis of Short-Line Fault Tests for Accurate Circuit Breaker Performance Specification

Abstract: The continuing program of analysis of circuit breaker short-line fault test data has culminated in a practicable method for getting complete performance and circuit information quickly from presently available test data and a simple, time-sharing computer program. A dynamic model of the circuit breaker arc near current zero using both the Cassie and the Mayr differential equations, has been solved by computer including interaction with resistance and capacitance shunts. By expressing the critical cases which just interrupt in terms of voltage and current slope coefficients, the model is fitted to key measurements from the test oscillograms. More precise specification of performance and its dependence on electrical parameters results.

Theoretical and experimental methods for evaluating discontinuities in microstrip

Abstract: Microwave circuits generally include a number of junctions and discontinuities at the interconnection of the various circuit limits and the resulting parasitic reactances can have a major effect on the circuit operation.The designer of waveguide and coaxial circuits has had available, for many years, a wealth of information on the parasitic reactances associated with the circuit elements and discontinuities, such as bends, T-junctions, transitions. Many elements can be evaluated theoretically and very accurate measurement techniques have also been devised in both media. Furthermore, small adjustments to the final circuits may easily be made using tuning screws, movable short-circuits, etc. In microwave integrated circuits the theoretical evaluation of circuit elements and discontinuities is difficult, experimental measurement is of limited accuracy and adjustment of the final printed circuit not easy to achieve.This paper will review the available theoretical and experimental methods for evaluating such discontinuities and present the available range of results. The equivalent capacitances can be obtained theoretically using fairly well known techniques but the inductance calculations are more difficult, although some progress has been made in this area recently. Theoretical data are important as accurate experimental measurements require considerable effort and there are a large range of configurations in use. To illustrate the effect of discontinuities on practical design the case of a microwave f.e.t. amplifier will be taken. Significant design errors can be shown to occur if the discontinuities are not allowed for. However, by using the data we now have available on the parasitics, fairly simple modifications can be introduced in the initial design to enable the desired performance to be more directly obtained.

Direct drive ballast circuit

Abstract: A direct drive electronic ballast circuit suitable for a fluorescent lamp load includes a high frequency oscillator inverter circuit having a tuned output circuit coupled to a load and to a drive circuit series connected to the load and dependent upon current flow therein. The high frequency oscillator inverter circuit is also coupled to a pulsed DC potential source which is shunted by a charge storage and isolating circuit energized by a feedback rectifier circuit which supplies energy whenever the potential from the pulsed DC potential source decreases below a given reference level. A relaxation type oscillator is coupled to the high frequency oscillator inverter circuit and provides a starting capability therefore.

Modified semiconductor temperature sensor

Abstract: A temperature sensor circuit is disclosed which employs a plurality of semiconductor junctions arranged either in a current-mirror configuration using a bias circuit and current source transistors or in a bridge configuration in order to provide a differential output voltage which is linearly proportional to temperature. The temperature sensor circuit is ideally suited for fabrication as an integrated circuit, and the differential output voltage is relatively insensitive to integrated circuit processing variations as well as power supply variations. By providing a differential output signal, the circuit is particularly useful in high noise environments such as automotive applications.

Mechanism and Properties of Point Contact W–Ni Diode Detectors at 10.6 µm

Abstract: The responsivity of the tungsten-nickel point contact diodes for the CO2 laser is investigated as functions of the contact pressure and the oxide thickness on the nickel post in order to determine the detection mechanisms of point contact MIM diodes at 10.6 µm. The data are compared with the current-temperature (I–T) characteristics and the theory based on the equivalent circuit model. A comparison of the above data and the I–T characteristics indicates that the point contact MIM diode acts as a tunnel diode. It is confirmed, from a comparison of the above data and the theory based on the equivalent circuit model, that the MIM diode operates as a square-law detector for the CO2 laser.