Showing papers on "Output impedance published in 1971"

Impedance related blood flow measuring device

Abstract: A cardiac blood flow measuring method and apparatus including two current electrodes and two voltage pick-up electrodes positionable in direct contact with the subject, with a circuit for applying a high frequency, low voltage current to the current electrodes and a circuit for measuring the total impedance across the voltage pick-up electrodes by using a summing circuit for adding selectively either a resistive or a reactive voltage to the subject''s total impedance voltage to determine selectively either the subject''s resistive impedance or reactive impedance with the reactive impedance being employed to measure cardiac blood volume flow.

High frequency matched impedance microcircuit holder

Abstract: A high frequency (greater than 108 hertz) microcircuit holder having a predetermined characteristic impedance that matches the impedance of the incoming transmission lines. The package is designed to achieve maximum power and/or signal transfer to a microcircuit hermetically sealed in the package. The characteristic impedance of the holder is reduced by a predetermined capacitance established between an input contact and a metal base plate. The impedance of the input contact is increased by reducing the cross-sectional area of the input contact as it passes through the dielectric wall of the microcircuit package. This increase in the impedance of the contact reduces the effect of the dielectric surrounding the contact which otherwise would result in a decrease in the impedance of the contact.

Microwave impedance matching system

Abstract: An impedance matching device for automatically and continuously matching a time varying microwave load to a fixed frequency microwave power source and its output line.

Self-biasing inverter

Abstract: A self-biasing inverter circuit comprises a load device and a semiconductor driving field effect transistor connected in series with a low-impedance device across a voltage source. The input is impressed on the gate terminal of the driving FET and the output is taken off the junction between the driving FET and the load device. A second field effect transistor having a high output impedance is connected between the source of the driving FET and the negative side of the voltage source and has its gate terminal connected to the inverter output. In this manner the source of the driving FET is biased to a negative voltage level sufficient to maintain said driving FET in the nonconductive state even for logic ''''O'''' signal more negative than threshold. In addition the bias signal is automatically diminished as a logic ''''1'''' input is impressed on the gate of the driving FET to aid in rendering the driving FET conductive.

Biquadratic sections using generalized impedance converters

Abstract: A low-sensitivity RC-active biquadratic section is proposed which employs a generalized impedance converter embedded in a simple passive RC-structure. This may be used to realize complex high-Q pole-pairs and transmission zeros. The multi-parameter sensitivity of the transfer function is independent factor. A high-quality narrow-band elliptic band-pass filter is given as a example.

Tables of Impedance Matching Networks Which Approximate Prescribed Attenuation Versus Frequency Slopes

Abstract: Tables of normalized lumped lossless two-section impedance matching networks, which closely approximate -4, -5, and -6 dB per octave attenuation versus frequency characteristics are provided. Impedance transformation ratios vary from 20:1 to 100:1. Bandwidths range from 30 to 67 percent. The networks are particularly suited to broad-banding of RF power transistor stages. Measured performance of a 12-W, 225-400-MHz transistor stage illustrates application of the designs.

Static hazard detector for isolated alternating current supply lines

Abstract: First and second resistors are connected in series with respective capacitors at first and second junction points. The two R-C series combinations are connected between the two line conductors of an isolated AC supply line, with each capacitor being connected to a different line conductor. Each junction point is connected to one terminal of a respective full wave rectifier, and the opposite terminals of the two full wave rectifiers are connected to a third junction point. Current flow through each rectifier is controlled by a respective transistor, and the transistors are alternately triggered conductive by an oscillator. A photoelectric resistor, such as a cadmium sulphide resistor, is connected in series between the third junction point and one terminal of a third full wave rectifier having an AC potential supply thereto so as to serve as an interposed source of DC potential. A lamp subjected to the voltage of the supply line is operatively associated with the photoelectric resistor so that the impedance of the detector circuit, or the ''''source impedance,'''' is varied so that the detector current is maintained at a constant value over the entire voltage range of from 102v to 132v, for a nominal 120v AC supply. The other terminal of the DC source is connected to one terminal of a milliammeter whose opposite terminal is grounded, and diode means are connected to the millianmeter so that fault current can flow therethrough in only one direction. The milliammeter, through the mentioned circuitry, is connected alternately to the first and second junction points for flow of fault current alternately from the line conductors in only one direction to ground through the milliammeter. A switching relay controls signal lights and an alarm, and normally maintains a ''''safe'''' lamp illuminated. Upon occurrence of a fault current flow through the milliammeter, an amplifier amplifies the fault current to energize the relay to switch connections to sound an alarm, to illuminate a ''''hazard'''' lamp, or to do both. Phase shift adjustment means are associated with the R-C series combinations, and a diode is connected in by-pass relation with the third full wave rectifier to direct reverse current flow in by-pass relation to the third full wave rectifier.

Sense amplifier for high speed memory

Abstract: A sense amplifier for use in the interrogation of a phototransistor matrix employs an electronically controlled impedance in parallel with the load resistor of each column. The electronically controlled impedance substantially reduces the time constant of electrical noise resulting from row selection. Additionally, a balancing capacitor functions to cancel the transient which results from the switching of the controlled impedance.

Input circuit for a television tuner

Abstract: A television tuner having an AGC controlled PIN-diode attenuator between the aerial terminals and the first transistor. The attenuator is formed in such a manner that its output impedance in case of continuing control deviates to an increasing extent from the transistor input impedance so that a considerable improvement of the signal-to-noise ratio is obtained.

Dynamic Properties of Impulse Measuring Systems

Abstract: After some basic considerations the dynamic properties of the measuring system are subjected to a general examination based on a number of responses, characteristic of the system. It is demonstrated that an impulse circuit has an internal impedance different from zero, for which reason the interaction between the generator and the measuring circuit is of paramount importance to the voltage across the test object. Based on the measured values the determination of the applied voltage is considered.

Field effect device and circuit having high current driving capabilities utilizing such device

Abstract: High speed, high voltage swing, low output impedance clock circuit is described. The circuit is designed to provide high current drive and uses a novel field effect device to resistively couple supply voltage to output voltage. The invention further relates to the field effect device per se.

Arrangement for decoding a four-level signal

Abstract: A device for decoding a four-level signal comprising two mutually connected digital circuits which are each provided with a current source and an associated switching member so as to connect the current source to an output impedance associated with the relevant digital circuit, the switching member associated with one digital circuit responding to a previously determined amplitude value of the input signal applied to the two digital circuits, and the switching member associated with the other digital circuit responding to a certain first or second amplitude value of the input signal dependent on the position of the switching member of the first digital circuit.

Improved Buffer Amplifier for Incorporation Within a Biopotential Electrode

Abstract: An amplifier for an active electrode is described which requires only a two-conductor connecting cable, is current limiting for patient safety, and has essentially unity voltage gain. In addition, the output impedance is lower and the input impedance has more adjustment latitude than is possible with a conventional source follower.

Tone ringer with a negative impedance amplifier

Abstract: A tone ringer device that includes an electroacoustic converter having a pair of electric terminals directly connected to the ports of a two-port amplifier having a negative impedance. A rectifier bridge circuit converts the ringing signals into a DC supply voltage for the amplifier. At a given frequency, the electroacoustic converter exhibits an electrical impedance between its terminals having a maximum magnitude with a zero phase angle.

Electronic musical instrument with expression control device for simultaneously controlling different tone signals by different amounts

Abstract: An electronic musical instrument includes two different music part playing sections such as an organ section and a rhythm section. The tone signal from the organ section is applied to an amplifier followed by a loudspeaker through a variable resistor for expression control, while the tone signal from the rhythm section is applied to the amplifier through a resistor having a resistance higher than the minimum resistance of the variable resistor and lower than the maximum resistance of the same. The input sides of both resistors are shunted by another resistor having a resistance comparable with the output impedance of the playing sections. When the variable resistor is operated, the rhythm section signal is subjected to volume control of a narrower range than the organ section signal.

Electrical impedance networks

Abstract: 1,244,032. Gyrators. POST OFFICE. 4 Feb., 1969 [9 Feb., 1968; 22 Oct., 1968], Nos. 6533/68 and 50113/68. Heading H3U. A gyrator comprises a pair of differential amplifiers A1, A2 interconnected by resistors R1, R2, R3 and impedances Z1, Z2 one of which is resistive, the inverting input of A2 being connected to either input of A1 as indicated by the link BC. If resistor R3 is considered as an external load, the network constitutes a threeterminal network with an input terminal T1, an output terminal at the + input of A2 and a common terminal T2 (earth). In Fig. 4A, the load resistor R3 is constituted by a T network RA, RB, RC and is connected to two gyrators NA, NB each of which comprises a capacitor as the reactive impedance (Z1 or Z2). This arrangement is equivalent to an inductive T network, Fig. 4B (not shown). The network may be formed as an integrated circuit.

Low-pass active parallel-t filter with zero source impedance

Abstract: The input of the capacitive series arm contains two capacitors to function as the first series capacitor and also as an input voltage divider, the divider being connected between a source of input signal and the capacitive series arm to provide low-pass characteristics. Compared with low-pass filters using resistive voltage dividers, the resistance between the series capacitors and the source of input signal is low, and therefore the series capacitive arm has true reactance.

Variable impedance circuit

Abstract: This invention describes a circuit having a variable impedance which varies in accordance with the input signal level. The inventive circuit is used in conjunction with the deemphasis circuit ordinarily employed in FM and other types of radio receivers. By varying the impedance between the output of the deemphasis circuit and the ground, the sensitivity of the audio frequency stage of the receiver is automatically varied. The variation in sensitivity increases the receiver's ability to reject interference and weak signals. The inventive circuit includes two parallel impedance paths connected between the output of deemphasis circuit and the ground reference. The first path is a fixed impedance path and the second contains a voltage sensitive switch. The impedance of the second path is a function of the current through the voltage sensitive switch and therefore the receiver sensitivity varies directly with the variation in current through the switch when the switch is in a conductive condition.

Imperfectly Conducting Dipoles

Abstract: For many purposes the conductivity σ of copper is sufficiently high so that no significant differences exist between the distributions of current and the admittances of copper antennas and the physically unavailable but mathematically convenient perfectly conducting antennas. The discussion and the tables in Section 2 assume σ = ∞ or z i = r i + jx i = 0, where z i is the internal impedance per unit length. In this section the properties of cylindrical antennas with nonzero values of z i are considered. The basis of the results presented is given in three papers.1,2,3 The impedance per unit length of the cylindrical antenna is conveniently expressed in terms of the dimension-less real parameter $$\Phi_i = 2\lambda r^i/\zeta_0$$ where r i is the resistance per unit length, λ is the wavelength in air, and ζ0 ≐ 1207π ohms. Typical graphs of the distributions of current along cylindrical antennas that are a half wavelength and a full wavelength long when perfectly conducting are shown in Figs. 3.1 and 3.2, with Φi as the parameter. Typical graphs of the admittance of resistive dipoles are shown in Fig. 3.3, and graphs of the impedance in Fig. 3.4. The efficiency is shown in Fig. 3.5. Tables 3.1 and 3.2 give numerical values of the admittance and the impedance, respectively, of resistive dipoles for a wide range of values of h/λ and Φi.

Equivalent Circuits and Coupling Coefficients of Cavity Resonators

Abstract: Consider a cavity resonator of arbitrary form, with resonance frequency f0 = ω0/2π and unloaded quality factor Q0, coupled with a source of internal impedance Z0 via a waveguide (say, rectangular) of characteristic impedance Z0 (see Fig. 20.1).

Signal coupling circuit

Abstract: This application describes a coupling circuit for coupling one or more signal sources to a common load without disturbing any of the coupled circuits. Each coupling circuit comprises a pair of amplifiers and a two-winding transformer. One amplifier, whose output impedance is much less than the load impedance, is connected to the transformer secondary winding. The other amplifier, whose output impedance is much larger than the load impedance, is connected to a center-tap on the transformer primary winding. The load and a matching impedance are connected to opposite ends of the primary winding. When more than one source is to be coupled to the load, the transformer primary windings are connected in series. A similar arrangement can be used at the input end of each amplifier. The suggested network can be used as the error injection network of a feed-forward amplifier.

Signal transmission in recorder systems with impedance transformation

Abstract: A technique for coupling high frequency energy to a recording transducer. The impedance transforming capability of a transmission line is utilized to transform the impedance of the recording transducer to a value which is matched to a source of operating signal for the transducer.

Interchanger 1 circuits

Abstract: A ternary logic circuit provides the Interchanger 1 logic function whereby for an input of levels 0, 1 or 2 there arises an output with levels 2, 1 or 0, respectively. A transistor current switch has two current paths only one of which includes a load impedance, the other current path bypassing the load impedance. A current source provides two units of current. Either none, one or both of the current units flow in the load impedance to provide the respective output levels, depending upon the input signal.

Transistor S parameter measurement: corrections for 2-port common-electrode impedance and the corresponding 2-port to 3-port transforms

Abstract: In 2-port transmission-parameter measurements on active devices, a residual common-electrode impedance can cause serious errors, particularly in the common-emitter configuration. Transforms are given which enable the true S parameters to be derived in terms of the measured parameters and the common-electrode impedance. It is shown that the inverses of these transforms can be used to derive the 3-port S parameters in terms of measured 2-port values. It is also shown that a unique relationship exists between the 2-port driving-point s parameters in the three configurations, which can be used as a partial check on system accuracy without the need for transformation to 3-port parameters.

Fluidic amplifier or modulator with high impedance signal source means

Abstract: A fluid repeater connects a high impedance sensor to the nozzle of a fluidic modulator such that the nozzle is coupled to the respectively low output impedance of the repeater instead of the high sensor output impedance. The repeater is of the leak type or a fluidic cathode follower shown in U.S. Pat. No. 3,499,458. A fluid controller includes a plurality of high impedance signal sources and lines individually connected through repeaters to an impact summing modulator as a summing point connected to a diaphragm amplifier. The output of the repeaters can be connected directly to the opposed summing signal nozzles of an impact modulator, to a transverse deflection control nozzle; singly or in combination with a non-deflecting opposing modulating difference signal. A feedback restrictor connects the output of the diaphragm amplifier to the modulator. The repeaters in the circuit essentially eliminate all loading and attenuating of the high impedance sensors and permit a substantial simplification in the fluidic circuitry. Suitable "Ratio" and calibrating restrictors connect a regulated pressure supplying to the summing impact modulator. This provides a greatly improved controlling receiver of simplified, modular construction. An integrator may be readily formed by connecting a capacitor, coupling resistor and positive feedback restrictor to the input side of the controlling receiver.

Amplifier with input and output match

Abstract: This application describes an amplifier comprising two active stages having mutually inverse input and output impedances whose magnitudes are at least an order of magnitude greater or less than the impedances of the external circuits to which the amplifier is connected. At the input end, the signal source is coupled directly, or by means of a transformer, to the high input impedance active element, and through a matching series impedance to the low input impedance active element. Similarly, the high output impedance active element is coupled directly, or through a transformer, to the useful output load, while the low output impedance active element is coupled thereto through a series impedance.

Transmission line impedance matching circuit

Abstract: An impedance-matching solid state amplifier circuit for an antenna circuit in which the impedance matching circuit can be connected at either terminus of the transmission circuit or at any point therebetween and in which the amplifier circuit need not be relied upon for any tuning effect as it relies upon the reflected impedance of the load in the matched impedance transmission circuit.

Digital pulse signal transmission circuit

Abstract: A digital pulse signal transmission line circuit is disclosed whose impedance is matched to the output impedance of the transmitter circuit for both an outflow current and an inflow current. An active element such as a transistor is connected in parallel with the input to the transmission line and a unidirectional switching means is connected in series with said transmission line so as to switch the transistor. When the outflow current flows, the unidirectional switching means generates a forward voltage drop due to said outflow current and this voltage drop cuts off the transistor. When the inflow current flows, the unidirectional switching means is cut off and said inflow current flows through the transistor which becomes conductive and causes the output impedance to decrease. As a result of this, the impedance of the digital pulse signal transmission line circuit is always matched to the output impedance of the transmitter circuit.

Techniques for broadband control of radar cross sections

Abstract: : Methods of realizing the load impedance required for radar cross section control of conducting bodies are discussed. It is shown that passive loading, using frequency-dependent dielectric/magnetic materials in a radial or coaxial line, requires a frequency dependence which is not exhibited by any known material. A number of active synthesis approaches are examined, with emphasis on those using the Negative Impedance Converter (NIC). Experimental results are given for a particular NIC realization operating in the 5 - 10 MHz range; the circuit is shown to be capable of producing the load impedance required for a cross-section reduction of 13dB or more over a 2:1 bandwidth.