Showing papers on "Output impedance published in 1977"

A general method for determining resonances in transformer windings

Abstract: This paper presents a method for calculating terminal and internal impedance versus frequency for a lumped parameter model of a transformer The transformer's total frequency response can be accurately determined from this impedance data directly, ie, the terminal resonance and anti-resonance and internal amplification factor characteristic can be calculated for a single or three-phase transformer model Since most equipment associated with power system operation can be accurately modeled with lumped parameter networks, this method also provides an accurate, straightforward method for determining the resonance characteristic of those systems An additional significance of this method is that the accuracy of the calculation is limited only by the user's ability to represent the equipment or system Heretofore, the accuracy of this calculation was limited by the simplifying assumptions required of the network model by each solution method This paper presents the definitions and mathematical theory underlying the method Two examples are presented in which comparisons are made between measured and calculated values for a helical air core coil and a 200 MVA single-phase autotransformer The agreement is excellent

Improved acoustic system for auditory research

Abstract: A closed acoustic system, based on the principles of lumped‐element and transmission‐line acoustics, has been developed for use in acute physiological experiments on small mammals. Through the appropriate utilization of a high‐quality push‐pull electrostatic earspeaker (Stax, SRX), a low‐impedance sound source having a relatively flat frequency response and a bandwidth of over 30 kHz is obtained. The output impedance of the source is increased by means of a lumped acoustic resistance in order to match the characteristic impedance of a uniform delivery line. The characteristic impedance of the delivery line is selected so that acoustic stimuli are propagated from the source to the eardrum without the introduction of substantial amplitude and phase distortion. Sound near the eardrum is coupled to a 12‐in. precision condenser microphone through a high‐impedance uniform probe line that is terminated in its characteristic impedance over the range of higher sound frequencies. When electrical equalization of +6 ...

Monolithic nullor-a universal active network element

Abstract: The design of a monolithic integrated nullor is described. It is a universal active element with floating input and output ports and with large internal gain. The element consists of a differential input stage, a symmetrical level shift stage, and a differential output stage. In the latter stage the collectors of a long-tailed transistor pair function as a pair of connected vessels for the output currents at high common-mode output impedance. This gives the output port its floating character. The element is capable of conveying a potential from one input terminal to the other input terminal and a current from one input terminal to the other output terminal at an accurate unity gain. The total inaccuracy of these operations is in the order of 2/spl times/10/SUP 4/ at signal voltage levels of 1 V and 1 mA. The element has a bandwidth of 25 MHz and can handle maximum signal values of 10 V and 1 mA. The availability of such universal active elements makes it possible to minimize the number of active elements and passive precision elements in implementation of analog system functions.

A 50-ohm input impedance for helical beam antennas

Abstract: A helical beam antenna with uniform conductor size has a nominal impedance of 140 ohms. This may not be convenient for some applications. The purpose of this note is to call attention to the fact that the impedance can be adjusted to 50 ohms by increasing the conductor size close to the feed point at the ground plane. This lowers the characteristic impedance of the conductor-ground plane combination (acting as a transmission line) and transforms the helix impedance to a lower value over a substantial bandwidth

Computer simulation of gallium arsenide field-effect transistors using Monte-Carlo methods

Abstract: A gallium arsenide planar field-effect transistor (f.e.t.) structure is simulated using a particle-mesh computer model. The model incorporates two dimensions in configuration space and three dimensions in k-space; with a full description of the material scattering cross-section which is implemented using Monte-Carlo techniques. The f.e.t. static characteristic has been calculated together with the lumped equivalent-circuit paramters. A comparison is made between devices with and without substrate. Detailed information about electrostatic potential and valley population profiles is presented for the first time. Cole-Cole plots of complex output impedance are used in determining device frequency response.

Theory of the Signal Transfer and Noise Properties of the rf SQUID

Abstract: The forward and reverse interactions between the SQUID input and output via the weak link are investigated in detail and presented in the form of an electronic equivalent circuit of the SQUID. The input and output impedances and the gain of the SQUID are given. The noise properties for all kinds of source impedances are computed and optimal values derived.

Loudspeaker lower bass response using negative resistance and impedance loading

Abstract: An apparatus and method for improving the bass response characteristics of an electrodynamic loudspeaker is described. The loudspeaker normally exhibits actual mechanical parameters such as damping, compliance, and mass which normally determine the bass response and lower cut-off frequency of the loudspeaker. The method and apparatus of the present invention cause the loudspeaker to exhibit apparent mechanical parameters which differ from the actual mechanical parameters to substantially change the effect of the actual mechanical parameters on the bass response. The apparatus in a preferred embodiment includes an electrical network through which electrical energy corresponding to the sound to be reproduced is applied to the voice-coil of the loudspeaker. The electrical network has an effective output impedance including a negative impedance in series with a plurality of impedances connected in parallel. The value of the negative impedance (including negative resistance) is chosen to be substantially equal to the impedance of the voice-coil. The plurality of parallel impedances have values which cause the loudspeaker to exhibit apparent mechanical parameters which are substantially different from the actual mechanical parameters in the bass response of the loudspeaker.

Package for push-pull semiconductor devices

Abstract: A semiconductor package for containing two individual devices such that they may be externally connected in a push-pull relationship. Two transistors, each having an input and output pad are formed on the same dielectric wafer, in a spaced relationship with each other and a ground plane so as to form two separate transmission line paths. The transistors are wired either in a grounded emitter or grounded base configuration. A shunt inductor is formed by a metallized strip or lead bond from the collector of one transistor to the collector of the other transistor. This inductor reduces the influence of the parasitic capacitance in the equivalent output circuit of the transistors. Since the collectors of both transistors are at the same DC level it is not necessary to include a DC blocking capacitor in series with the inductor. This increases the reliability and the reproducibility of the circuit because bonding wires necessary in prior devices to connect the blocking capacitor in series with the output inductance is not necessary. This packaging technique increases the output impedance, decreases the internal losses, and increases the bandwidth when wired as a push-pull circuit.

Detection of 10‐μ radiation with point‐contact Schottky diodes

Abstract: Point‐contact Schottky diodes have been used to detect 10.6‐μ radiation. Best results were obtained with n‐Ge/W contacts. These gave voltage responsivity about an order of magnitude larger than typical metal‐oxide‐metal point contacts under zero‐bias conditions, although with higher source impedance.

Test apparatus for obtaining impedance settings for hybrid balance networks

Abstract: Impedance settings are obtained automatically for manually adjusting a network to obtain a driving point impedance substantially equal to a particular unknown impedance. Discrete impedance settings for setting up, for example, a manually adjustable hybrid balance network are obtained by employing a hybrid network, a noise signal source, at least first and second automatically adjustable balance networks and at least first and second control circuits. An impedance to be matched, for example, a 2-wire telephone cable, is connected to the hybrid. Signals detected at the cable and at the inputs to the respective balance networks are employed to generate control signals for adjusting impedance elements in the automatically adjustable balance networks. Impedance elements in the first balance network are continuously adjusted to match substantially exactly the impedance of the cable. Then, the most sensitive of the corresponding control signals is rounded off to a discrete value and supplied to adjust a corresponding discretely adjustable impedance element in the at least second adjustable balance network. The second control circuit then generates signals for adjusting the remaining impedance elements in the second balance network to obtain the most optimum driving point impedance to match the cable impedance. Values of the impedance control are displayed in binary form to be used by a craftsperson for setting up a corresponding manually adjustable balance network to match the particular cable connected to the hybrid.

Attenuator with compensation of impedance errors

Abstract: Step attenuators wherein a number of individual attenuators are connected in series, with a switch across each individual attenuator, are well known. By opening and closing particular combinations of the switches, any one of a number of different values of attenuation may be selected. Each individual attenuator has in the past, as well as in the present invention, had a characteristic impedance equal to the impedance of both the signal generator (which feeds the input of the step attenuator) and the load (connected across the output of the step attenuator). However, the switches for selecting the individual attenuators may have substantial resistance especially where solid state switching diodes or mercury wetted reed relays are employed. The latter type switches display resistances caused by skin effect at highter frequencies. This causes inaccuracies of the attenuation steps due to mismatch, in prior art systems of the type described above. To avoid the mismatch, an additional impedance is added to the circuit, between each adjacent pair of attenuators, to form a network. The network includes the resistance of the switches. This network is designed to have a characteristic impedance equal to the characteristic impedance of each attenuator. Stated otherwise, it has the same characteristic impedance as the impedance of the signal generator and the impedance of the load.

Oxygen sensor temperature monitor for an engine exhaust monitoring system

Abstract: A vehicle engine includes an exhaust monitoring system with an exhaust mounted oxygen sensor and apparatus for processing the sensor output voltage into an exhaust constituent signal which may, for example, be used to control the air-fuel ratio of the engine fuel supply to a substantially stoichiometric ratio, the apparatus including a low pass filter which suppresses components of the signal greater in frequency than a predetermined cutoff frequency. An alternating voltage generator effective to generate a square wave of at least the cutoff frequency is connected through a reference impedance, a capacitor and the oxygen sensor in series to ground, thus creating a voltage divider with an output between the reference impedance and the sensor internal impedance, the voltage at the output having a peak-to-peak amplitude which varies inversely with sensor temperature. The voltage at the output is provided to a peak detector, which generates therefrom a signal representing the temperature of the oxygen sensor. The low pass filter in the closed loop fuel control and the capacitor protect the exhaust constituent signal from distortion by the alternating voltage.

Electronic circuit having its impedance controlled by an external signal

Abstract: This disclosure relates to an electronic circuit which has a controllable impedance. This type of circuit is well suited for application in noise suppression circuits or in signal compression/expansion circuits. The circuit has two stages. The first stage is a voltage to current converter. The second stage is a variable gain current amplifier. The output of the second stage is connected by a feedback loop to an input of the first stage. The circuit has a variable impedance which can be controlled by an external signal. The imput impedance of the circuit is linearly related to the applied control signal.

Crosspoint bias circuit arrangement

Abstract: A semiconductor transmission circuit arrangement which utilizes symmetrical transmission transistors and bias circuitry which exhibits a high output impedance and is arranged to maintain equal d.c. bias currents in the base and the emitter/collectors of the transmission transistor. A multiple collector transistor is utilized as a primary current source and a current mirror circuit is used as a control arrangement.

Discharge lamp lighting device

Abstract: PURPOSE:To provide a discharge lamp lighting device, in which a current-limit element is separated from emans for supplying the oscillatory output of a boosting circuit to a discharge lamp so that the current-limit impedance and the oscillatory output impedance may be preset at the maximum efficiency independently of each other, thus allowing the maximum exhibition of the every cycle lighting system.

Comments on "Transmission-Line Transformation Between Arbitrary Impedances" [Letters]

Abstract: The solution given by the author of the above letter, for the characteristic impedance of the line transformer, has been given before (see H. Jasik, Antenna Engineering Handbook, McGraw-Hill, 1961, paragraph 31.3, p. 9). Jasik also gives the correct length of the transformer whereas Milligan and also apparently Day (IEEE Trans. Microwave Theory Tech., vol. MTT-23, p. 772, 1975) give the distance between load and source impedance along the impedance circle, which is not the length of the desired transformer since the transformer should produce at the source the conjugate of the source impedance if matching, which presumably means power matching is desired. Thus in the expression given by Milligan for length, X/sub 2/should be given as -X/sub 2/, which will now agree with Jasik's expression.

Battery discriminator circuit for smoke detectors

Abstract: A battery powered smoke detector includes a battery powered discriminator circuit which periodically senses the chemistry of the battery represented by its volt-ampere output and internal impedance. An external impedance comparable to the alarm circuit load on the battery is connected in parallel with the battery such as to trigger an alarm when the battery energy delivered through the impedance approaches a level inadequate to drive the alarm.

Impedance trim network for use in integrated circuit applications

Abstract: An adjustable impedance network is disclosed which is suitable to be used in monolithic circuit applications to eliminate problems caused by processing tolerances. One example of such use is to employ the impedance network in the collector circuit of a differential amplifier to eliminate input voltage offset errors. The impedance network includes a plurality of impedance elements serially coupled together between first and second terminals which in the above example would be coupled to respective collector output electrodes of the differential amplifier. Each impedance element is initially electrically shorted by a respective one of a plurality of thermally machinable metallic link. In addition, a selected number of the impedance elements are electrically shorted to a common terminal by two additional metal links which are serially connected together across said selected number of impedance elements. The impedance elements are binary weighted to provide a maximum number of trim values. A laser apparatus may be used to cut or machine appropriate links to open circuit the link to add predetermined resistance between either the first or second terminal of the network and the common terminal thereof. Thus, in the above example, resistance may be added to either collector load resistor of the differential amplifier to compensate for mismatch in the transistors comprising the amplifier.

Active load circuits

Abstract: An active load circuit is interconnected between a signal source such as a pickup cartridge and an amplifier which acts as an impedance matching resistor. An equivalent resistance provided by the amplifier as viewed from the signal source equals a required resistance for impedance matching, and the noise voltage is considerably reduced as compared with that produced by a conventional matching resistor.

Junction Impedance Measurements of Diodes by a Simplified Lock-In Amplifier

Abstract: A lock-in amplifier with most parts of its functional components substituted by integrated circuits is described here. This amplifier is far from expensive and is free from the trobles arising from temperature compensations and impedance matchings such as usually occur in conventional transistorized amplifiers. This instrument, operating at frequencies from 20 Hz to 100 kHz, has a noise rejection ratio of 40 dB and is suitable for junction capacitance and resistance measurement of diodes under reverse or forward bias.

Surface acoustic wave device

Abstract: PURPOSE:To increase input/output impedance by intervening a dielectric film having low dielectric constant between interdigital electrode and piezoelectric substrate.

The Locus of Points of Constant VSWR When Renormalized to a Different Characteristic Impedance (Letters)

Abstract: The locus of points of constant VSWR with respect to an impedance Z/sub 1/, when measured with equipment of characteristic impedance Z/sub 0/, other than Z/sub 1/, is found to be a circle that is easily constructed on a Smith chart. The use of a transparent overlay with various such circles converts any network analyzer with a Smith chart display to read swept VSWR values to the new impedance.

Audio-frequency power amplifiers

Abstract: An audio- or low-frequency power amplifier comprises a pair of output transistors which are opposite in a conduction type to each other and connected in a complementary push-pull circuit configuration in which an impedance element is connected between the bases of the paired output transistors whose bases are adapted to be applied with an input signal while the output signal of the amplifier is derived from the coupled emitters of the output transistors. The amplifier further includes a current stabilizer transistor having a base-emitter junction across which a fixed bias voltage is applied and a collector, the current from which is supplied to the impedance element thereby to provide a bias voltage for the paired output transistors. A first resistor is connected between the emitter of the current stabilizer transistor and one electrode or pole of a first d.c. power source while a second resistor is connected between the emitter of the current stabilizer transistor and the other pole of the d.c. source, thereby to maintain constant the bias voltages applied to the paired output transistors.

Power tool theft alarm

Abstract: The internal impedance loads of a plurality of electrical appliances on display are directly connected in series through their power switches and power cords by a connector strip to form a detection circuit. Interruption of the detection circuit is sensed by a relay to activate a power operated alerting device. Continuity of the detection circuit is maintained by plugging all of the power cords into the connector strip and holding all of the power switches closed by removable binding tape or the like.

HF receiver antenna with programme tuner - has controlling fourpole matching circuit between antenna and main impedance transformer

Abstract: TheHF receive antenna has a broadband impedence transformer coupled after the passive part of the antenna. It is made extremely small and eliminates the effects of extremely powerful unwanted transmitters. A fourpole network is connected between the passive part of the antenna and the impedance transformer. This matches the antenna output impedance to the input impedance of the impedance compared to the receiver impedance. The fourpole is tuned by programme selector. The impedance transformer may be a low-noise amplifier or a wound transformer.

Noise pulse generator

Abstract: PURPOSE:To make effective noise tests possible regardless of the low internal impedance of the AC power supply by connecting a thyristor and a condenser in series with the load and AC power supply and by supplying the discharge current of the condenser as a noise pulse with the thyristor.

Computer aided techniques for measuring performances of switching DC/DC regulators

Abstract: A practicable technique for measuring the dynamic performances of switching regulators in a testing laboratory is presented. The method is based upon the use of a mini computer for acquisition and further off-line processing of a suitably chosen perturbed signal. The selected signal is the closed loop transient response, to a step input in the load current or in the reference voltage. The processing is done after digital filtering according to Samulon's algorithm. The technique yields accurate amplitude and phase measurement of closed and open loop transmittance, output impedance ...etc..., without opening the control loop and in one shot.

Impedance compensation of transmission line

Abstract: An unconditionally stable impedance matching network for matching a nonloaded voice frequency transmission line to the standard impedance of a repeater on said line is provided.

Circuit network showing proper equivalent impedance between two network terminals

Abstract: A circuit network with a pair of operational amplifiers and impedance elements, to show equivalent impedance, between two network terminals, of a value either well reduced or enlarged from the impedance of the impedance elements. The network may thus function as idealized diode when the impedance elements are diodes, or may be of large equivalent capacitance or inductance, as the impedance elements are capacitors or inductors.

Distortion corrector for wide-band transistorized amplification stages

Abstract: of the disclosure Corrector consisting in arranging, in the circuit of an electrode of a transistor, or between two transistorized stages, of an amplifier to be corrected, a circuit equipped with at least one varactor in parallel with a resistance and fed by the current flowing through the transistor or transistors under a source impedance which is sufficiently low by comparison with that of this circuit, the effects of the variation in the capacitance of the varactor or varactors, in dependence upon the signal, compensating those due to this varactor effect.