Showing papers on "Output impedance published in 1979"

Rogowski coils: theory and experimental results

Abstract: The theory is given of the voltage output of a Rogowski coil excited by a current pulse flowing along the axis of the coil. In this theory the Rogowski coil is considered as a delay line. The results do not differ from those obtained usually by considering the coil as a voltage source dφ/dt with an inductive output impedance. Details are also given of the design of two Rogowski coils and their working modes are fully analyzed.

Impedance parameters and the state-of charge. I. Nickel-cadmium battery

Abstract: The problem of nondestructive determination of the state-of-charge of nickel-cadmium batteries has been examined experimentally as well as theoretically from the viewpoint of internal impedance. It is shown that the modulus of the impedance is mainly controlled by diffusion at all states of charge. Even so, a prediction of the state of charge is possible if the equivalent series/parallel capacitance or the alternating current phase shift is measured at a sufficiently low a.c. test frequency (5–30 Hz) which also avoids inductive effects. These results are explained on the basis of a uniform transmission-line analog equivalent circuit for the battery electrodes.

Battery monitoring means for an implantable living tissue stimulator

Abstract: A battery monitoring means for an implantable living tissue stimulator system in which various battery voltages are telemetered to an external receiving means, these voltages being related to the internal impedance of the implanted battery. More specifically, a battery loading circuit is provided which incorporates a switch means for loading the battery in accordance with a predetermined sequence. In a specific embodiment, first and second resistors are sequentially connected across the battery. The battery output voltage is telemetered to an external receiving means during this sequential connection. By knowing the values of the two resistors, the internal impedance of the battery can be calculated, this impedance being related to the remaining life of the implanted battery.

Impedance parameters and the state-of-charge. II. Lead-acid battery

Abstract: The determination of the state-of-charge of the lead-acid battery has been examined from the viewpoint of internal impedance. It is shown that the impedance is controlled by charge transfer and to a smaller extent by diffusion processes in the frequency range 15–100 Hz. The equivalent series/parallel capacitance as well as the a.c. phase-shift show a parabolic dependence upon the state-of-charge, with a maximum or minimum at 50% charge. These results are explained on the basis of a uniform transmission-line analog equivalent circuit for the battery electrodes.

Loss compensation regulation for an inverter power supply

Abstract: An inverter power supply circuit that compensates for variations in the power supply's output voltage, which variations are due to variations in output loading, is disclosed. The input side of the circuit's DC-DC Converter-Inverter-Converter coupling transformer incorporates a compensation network having an impedance that is equivalent to the power supply's output impedance. Variations in the output loading cause corresponding proportional changes in the currents passing through the load and the compensating network. The changing current in the compensating network on the input side of the coupling transformer generates a corresponding changing voltage that is coupled, as a positive feedback, to the chopping transistor of the power supply to provide compensation for the variation in loading on the output side of the coupling transformer.

High bandwidth transversal filter

Abstract: A high bandwidth transversal filter is described having an input impedance matching network, a tapped delay line, a plurality of weighting amplifiers, a distributed summing circuit, and an output impedance matching network The delay line is implemented with a transmission line The input impedance of this transversal filter depends on the inductance and capacitance of the transmission line and the capacitance of the inputs of each of the FET's used as weighting amplifiers The gates of the FET's provide high impedance low loss taps of the delay line The weighting is accomplished by either varying the drain current of the FET's or by using capacitive voltage dividers to apportion the tapped signals The resulting weighted signals are applied to a distributed summing circuit which provides both high bandwidth summing and additional delays This summer is also implemented with a tapped transmission line The output impedance of this transversal filter depends on the inductance and capacitance of the summing line and the capacitance of the output of each FET The parameters of the transmission lines constituting the input delay line and the distributed summer can be selected to provide broadband impedance matching for the input and output of the filter The FET's thus act as high impedance taps, as weighting amplifiers, and as part of the input and output impedance matching networks

Selective switching circuit of signal transmission line

Abstract: PURPOSE:To make it possible to select a transmission line without exerting an influence on a signal source, etc., by terminating a nonselective signal by impedance equal to a terminating impedance value all the time in simple circuit constitution including a switching method and amplifier. CONSTITUTION:The 1st route among input routes is provided with switching methode SW1A connected to a signal source and to the 2nd route, the other switching method SW1B and amplifier AMP are cascaded; and AMP is so composed of operational amplifier OPA with series resistance element Rz and feedback resistance Rf that its input impedance will be queal to terminating impedance Z0 and the input of AMP will be set out of phase with its output. Therefore, method SW1A is opened after the selection to close method SW1B, and the terminating impedance viewed from the signal source becomes equal to impedance Z0 while a leaking signal having passed through method SW1A and OPA is canceled at the output side of mixer MIX.

GaAs Dual-gate FET frequency discriminator

Abstract: A microwave frequency discriminator comprising a dual-gate field effect transistor (FET) amplifier, bias circuits and a detector. The FET is biased to produce an output RF signal within a predetermined frequency bandwidth in response to an input RF signal. A limiter provides a substantially constant power level of the input RF signal to the FET. A detector biasing circuit is used to match electronically the output impedance of the FET to the input impedance of the detector. At such impedance conditions a dc output voltage of the detector varies substantially linearly throughout the frequency bandwidth as a function of the frequency of the input RF signal, approximating the characteristic of a frequency discriminator.

Oxygen monitoring circuit with built in testing means

Abstract: An oxygen monitoring circuit is disclosed. The circuit comprises a high impedance follow and hold circuit adapted for connection to an oxygen probe, a readout unit connected to the high impedance follow and hold circuit, a programmer normally connecting the oxygen probe to the high impedance follow and hold circuit but momentarily disconnecting the oxygen probe from the high impedance follow and hold circuit for a relatively short time interval and loading it with a resistor having an impedance relatively higher than the normal impedance of the probe, and a probe failure indicator connected to the outputs of the oxygen probe and of the high impedance follow and hold circuit for detecting any significant change in impedance of the probe and resistor combination as a result of loading and for operating an alarm when the impedance of the probe exceeds a predetermined value.

A Universal Four-Pair Impedance Bridge

Abstract: A wide range 10 ppm four-terminal-pair audiofrequency impedance bridge is described. The bridge can be operated either in an impedance mode, for self-inductance, mutual inductance, and resistanre measurements; or in an admittance mode for capacitance and conductance measurements. The frequency range for full aecuracy is 40 Hz to 2 kHz. Maintenance of the calibration of the bridge is facilitated by the use of transformer ratios to extend the range of a small number of precision components, and extensive use is made of electronic techniques to automate auxiliary balances.

Impedance matching by the combined effects of the outer and middle ear

Abstract: When the impedance mismatch between air and the oval window is computed by considering the latter as a small piston in a baffle, and taking the appropriate source impedance into account, it can be shown that the mismatch is frequency dependent and may be greater than 50 dB at 100 Hz. The middle ear transformer by itself is inadequate to compensate for the loss of transmission due to the mismatch. Only at the frequency of the outer ear resonance does the combined action of the outer ear and the middle ear produce an estimated gain that roughly compensates for the loss of energy at the interface. Detailed computations are shown for cats, and some results applicable to the human ear are also included.

Device for measuring and indicating changes in resistance of a living body

Abstract: A device for measuring and indicating changes in the resistance of a living body including a single battery source, a means for setting a reference voltage level provided across the battery, a unity gain high input impedance and low output impedance buffer amplifier having as its input the reference voltage level, a balanceable resistance bridge having the output of the buffer amplifier applied thereto and having the living body coupled thereto as a part of the bridge, a meter amplifier for amplifying any imbalances in the bridge caused by changes in the resistance of the living body and a meter coupled to the output of the meter amplifier for indicating the changes in resistance of the living body.

Root canal measuring apparatus

Abstract: A root canal measuring apparatus can measure a length of a root canal without using an oral electrode. The apparatus is composed of an oscillating circuit having a relatively high output impedance, an output terminal connected to one output end of the oscillating circuit and also connected to a tooth electrode, another output terminal connected to the other output end of the oscillating circuit and also connected to a conductive portion forming an electrostatic capacity with a patient, and a display unit for displaying a variation in voltage between both the output terminals.

The development of a guide on surge voltages in low-voltage ac power circuits

Abstract: Surge voltages in ac power circuits become more significant with the increased application of miniaturized electronics in consumer and industrial products. A Working Group of IEEE has prepared a Guide describing the nature of these surges in ac power circuits up to 600 V, and is currently developing an Application Guide for using the environmental data defined in the Guide to improve protection. The Guide proposes two waveforms, one oscillatory, the other unidirectional, depending on the location within the power system. It also includes recommendations for source impedance or short-circuit current. This paper describes the data base and approach used by the Working Group and the recommendations proposed to represent typical surges, in order to obtain feedback for writing the Application Guide.

Microstrip Characteristic Impedance

Abstract: A recent paper by Bianco et al. gives five definitions of microstrip characteristic impedance which do not have the same frequency dependence. This paper shows that the most widely used definition can be based on wave-impedance and is a unique unambiguous characteristic impedance for microstrip, consistent with characteristic impedance definitions of other waveguiding structures.

High-resolution dc-voltage-biased ac conductance bridge for tunnel junction measurements.

Abstract: A simple, low‐cost conductance bridge circuit, which provides high‐resolution measurements of dI/dV and d2I/dV2 for a voltage‐biased load, is presented. A resolution in dI/dV for a 90‐Ω tunnel junction of several parts in 105 has been measured using a 35‐μV‐rms modulation level and a 1‐s postdetection time constant (Bn=0.25 Hz). The output impedance of the voltage source and the error in the conductance measurement are discussed. The output impedance of the circuit with an AD119 operational amplifier is 0.02 Ω. A detailed discussion of Johnson‐Nyquist, tunnel junction, and amplifier noise is presented.

Design method for linear amplifier

Abstract: A method of designing a linear rf amplifier comprising an output load impedance and an active device including the steps of (a) applying DC bias to the device, (b) applying two different frequency signals of an amplitude C, and (c) changing the value of the load impedance and recording the impedance value and associated C/I ratio for each impedance value (C/I being the ratio of amplitude C and amplitude I--the amplitude of an intermodulation product frequency). The last step (c) is repeated for a plurality of output levels. The above is repeated for a plurality of input power levels. The next step is selecting from the recorded information the impedance values corresponding to the maximum C/I ratio and recording the impedance values and corresponding C/I ratios, input power levels and output power levels. Then, choosing a desired C/I ratio from those recorded in the previous step and selecting the impedance value corresponding to the maximum output power level.

Impedance-matching network realized in microstrip technique

Abstract: An impedance-matching microstrip network for matching a predetermined impedance to a lower impedance over a wide frequency band having a tapered line section for transposing the predetermined impedance to a higher impedance. At least one quarter wave line section is coupled to the narrow end of the tapered line section for transposing the higher impedance to the lower impedance.

Closed loop mixture control system for internal combustion engine

Abstract: A closed loop mixture control system for an internal combustion engine comprises an exhaust gas sensor, a source of injecting a current into the exhaust gas sensor to develop a substantial voltage across the internal impedance thereof, and a variable reference setting circuit which establishes a variable reference voltage and reduces its value as a function of time such that the reference voltage lies between the maximum and minimum peak values of the output signal from the exhaust gas sensor.

Resonant element transformer

Abstract: An impedance matching device is created for transforming electrical impedes. The device has more stability at low impedances. A pair of coplanar coupled transmission line conductors are placed on a dielectric substrate so as to form a four port impedance device. The electrical parameters of the device, such as electrical length and even and odd mode impedance, are selected from design parameters determined by evaluating a determinant matched to a complex load impedance Zr. A specific example of matching a standard 50 ohm transmission line to an IMPATT diode is disclosed.

Musical instrument performance amplifier

Abstract: The output section of a musical instrument performance amplifier comprises a pair of high impedance power field effect transistors connected to an output transformer to provide a relatively low push-pull drain load that effectively presents a high impedance constant current source to a loudspeaker. The amplifier, having such high impedance constant current source output, amplifies and sustains instrument sound, provides large amounts of power to the speaker over a wide range of speaker impedances, and enables production of high power harmonics.

Impedance parameters and the state-of-charge. III. Zinc-manganese dioxide and magnesium-manganese dioxide dry batteries

Abstract: The problem of non-destructive determination of the state-of-charge of zinc- and magnesium-manganese dioxide dry batteries is examined experimentally from the viewpoint of internal impedance and open-circuit voltage at equilibrium. It is shown that the impedance is mainly charge-transfer controlled at relatively high states-of-charge and progressively changes over to diffusion control as the state-of-charge decreases in the case of zinc-manganese dioxide dry batteries. On the other hand, the impedance is mainly diffusion controlled for undischarged batteries but becomes charge-transfer controlled as soon as there is some discharge in the case of magnesium-manganese dioxide batteries. It is concluded that the determination of state-of-charge is not possible for both types of batteries by the measurement of impedance parameters due to film-induced fluctuations of these parameters. The measurement of open-circuit voltage at equilibrium can be used as a state-of-charge indicator for Zn-MnO2 batteries but not for Mg-MnO2 batteries.

High - Density High - Impedance Hybrid Circuit Technology for Gigahertz Logic

Abstract: A novel hybrid substrate technology suitable for use as a relatively dense interconnecting medium for very high-speed digital logic devices is presented. It has been well established that as the signal rise and fall times of logic circuits become extremely short, the propagation of these signals between devices must be conducted along transmission line structures. Therefore, hybrid substrate technologies must be capable of realizing interconnects between chips which possess desired highfrequency transmission characteristics. This implies a specific, uniform wave impedance, low attenuation, reasonably good isolation between signal lines, and the ability to provide for line matching at either the sending end or receiving end of any path. In order to obtain these transmission properties in a reasonably dense interconnect array, the structures and fabrication technologies must be chosen so that very small linewidths and spacings can be achieved, while maintaining the desired transmission characteristics. Another important consideration is related to the output impedance characteristics of the emerging high-speed digital circuit technologies. Currently, ECL technology is the most widely used for the implementation of complex digital systems requiring ultra-high switching speeds. However, predictions on the potential increase in achievable switching speeds for this technology are limited to 200 to 400 ps. One of the desirable characteristics of this technology is its reasonably low output impedance. This permits the interfacing to a relatively low impedance (50-70 \Omega ) for driving between devices in a conventional transmission line environment. Newer circuit technologies, such as that employing GaAs MESFET's, offer the potential of much shorter switching times (50 to 100 ps). However, this circuit family possesses an inherently higher output impedance when configured in large integrated arrays. Thus the characteristic impedance of the supporting transmission structure must be high in order to minimize the signal attenuation between communicating chips. In fact, a high-impedance transmission structure would be advantageous for any high-speed circuit family, in that it would reduce the amount of power required to drive the information between devices. For these reasons a fine-line monolithic hybrid substrate technology is proposed that can best meet these goals. Although there are several approaches that can be considered to obtain reasonably fine-line transmission structures, it will be shown that by using sapphire as a supporting structure, very narrow widths (5-10 \mum) of aluminum interconnecting transmission lines can be defined yielding 100 to 200-\Omega characteristic impedances.

Microwave integrated circuit package

Abstract: PURPOSE:To facilitate impedance matching by a method wherein a substrate which has integrated circuits for microwave is built perpendicular to a supporting board which has input and output terminals and line ends of integrated circuits are connected with input and output terminals, respectively, which protrude toward the direction of integrated circuit ends. CONSTITUTION:Input and output terminals 2, 3 and outer lead wires 4 are extended, being insulated with insulator 5 and vertically from a metal base, and characteristic impedance of terminals 2, 3 are adjusted to the specified value by arranging them. The ceramic substrate 6 has microwave integrated circuits 7, and also has input and output line ends 7, 8, line ends 10 for bias voltage circuit and a conductive film 11. According to this constitution input and output line ends 8, 9 have direct connections with input and output terminals 2, 3, respectively, not having intervening bends, and impedance matching for connecting parts is facilitated. Thus because line ends 8, 9 of microwave circuits and input and output terminals 2, 3 are protruded in the same or parallel direction, impedance matching is facilitated and package size can be reduced.

Slot-Coupled Tee Junction in Rectangular-Guide E Plane

Abstract: An expression for the equivalent circuit of a waveguide tee junction coupled through a narrow transerse slot of variable length is determined from self-reaction and discontinuity in modal voltage. Impedance loading on primary guide and coupling are deternined from the equivalent network parameter. A comparison between theoretical and experimental results is presented.

Variable reference mixture control with current supplied exhaust gas sensor

Abstract: Mixture ratio control for internal combustion engines supplies a constant current into an exhaust gas sensor to develop a voltage of a substantial magnitude in proportion to the initial high value of the gas sensor internal impedance during low temperature conditions. The voltage so developed decreases as a function of time corresponding to the decrease of the internal impedance with temperature. A voltage detector is provided to trigger the control system to operate in a closed loop mode when the gas sensor voltage is reduced to a level below a first threshold level. Responsive to the output of the voltage detector the supplied current is momentarily interrupted to allow the gas sensor voltage to drop rapidly to a level which is higher or lower than a second threshold level depending on the concentration of the sensed gas in the exhaust system. A second detector senses this voltage drop relative to the second threshold to determine whether the gas sensor output represents rich or lean condition. The reference point of the closed loop is raised or lowered in response to the output of the second detector and further decreased as a function of time such that the reference point lies within the range between maximum and minimum peak values of the gas sensor output signal.

Electrode impedance monitoring method apparatus for electrocardiography

Abstract: A patient's own heart is used as a voltage source for measurement of EKG electrode impedance. The amplitude of an EKG signal obtained while the EKG electrodes are shorted together with an impedance is compared to the amplitude of an EKG signal obtained under identical conditions except that the impedance short is not present. The value of the inter-electrode impedance is then equal to one less than the ratio between the unshorted amplitude and the shorted amplitude times the value of the shorting impedance. In a preferred embodiment, the value of the shorting impedance is made equal to the maximum permitted inter-electrode impedance. Then, if the amplitude of the EKG signal taken from a patient decreases upon temporary insertion of the impedance short to a value less than half of the EKG amplitude obtained without the impedance short, the inter-electrode impedance is too high.

Crystal oscillator implemented with CMOS technology

Abstract: In a crystal oscillator for solid state wristwatches, the input of an impedance converter is connected to the output of a complementarily connected transistor amplifier which performs linear operation within its essential operating range, to thereby stabilize and decrease the output impedance of the amplifier on the average. The impedance converter includes one or more active elements such as MOSFET's, junction type FET's and bipolar transistors. A quartz resonator is connected between the input of the complementarily connected transistor amplifier and the output of the impedance converter.

Electronic selector switch particularly for use in radioscondes

Abstract: The output of each of a plurality of CMOS inverting amplifiers is connected to a corresponding one of a plurality of impedances to be measured. A stepping circuit is connected to the inputs of the amplifiers. A voltage supply is connected to the amplifiers and provides a signal to be measured which is directed via a corresponding one of the amplifiers to an impedance measuring circuit connected to the impedances to be measured in common. The impedance measuring circuit produces an output impedance proportional to the impedances to be measured.