Showing papers on "Output impedance published in 1980"

Tuned-circuit RF-excited laser

Abstract: An RF-excited gas laser is improved by the addition of an inductor in parallel with a discharge resistance Rg and capacitance Cwg to form a tuned circuit having a resonance frequency such that the real part of the complex impedance of the discharge chamber is matched to the output impedance of a driving oscillator and by the use of an input circuit that compensates for the imaginary part of the discharge chamber impedance.

Arrangement for controlling the electrodes of an arc furnace

Abstract: An impedance controller is used for controlling electrode-to-bath spacing in an arc furnace. Measured quantities proportional to the electrode voltage and the electrode current are determined and an actual impedance value is formed from the measured values by means of a divider. The actual impedance value is compared with a predeterminable desired impedance value to derive a control signal. If in the event of a short circuit, the actual impedance value reaches a predetermined lower limit, a switching element sets into the controller a signal causing full drive, so that the electrodes are raised at maximum velocity. If the sum of the two measurement quantities becomes zero, the output of the controller is cut off.

Bridge-balancing system for measuring extremely low currents

Abstract: A bridge-balancing system for measuring minute current flows in devices having an extremely high impedance, the bridge having two sets of opposing arms to define input and output diagonals. A direct voltage is applied to the input diagonals and an amplifier having a high input impedance is connected to the output diagonals to yield an analog signal whose sense and magnitude depend on the degree to which the impedance of the device under test which forms one arm in one set differs from that of an adjustable high-impedance element forming the opposing arm of that set, a pair of fixed matching resistors defining the arms of the other set. The adjustable element is constituted by a field effect transistor operating in its variable resistance region wherein the extremely high impedance presented thereby depends on the applied gate potential. In the manual mode of the system, the impedance of the device under test is determined by varying the potential applied to the gate until a point is reached at which the signal is nulled and the bridge is in balance, at which point the impedance of the transistor matches that of the device under test and has a value which is a function of the applied gate potential. In the automatic mode, the analog signal is converted into a corresponding digital value which is evaluated in a microprocessor to determine the potential required to effect nulling, the microprocessor yielding a digital instruction that is converted into an analog control signal which is applied to a correction amplifier that imposes a nulling potential on the gate.

Battery monitoring means and method for an implantable tissue stimulator

Abstract: A battery monitoring means for an implantable tissue stimulator in which a signal related to the internal impedance of an implanted battery is telemetered to an external receiving means. More specifically, the implanted battery is loaded by a varible load until current flowing through the battery lowers its output voltage until it has a predetermined relationship with respect to a reference voltage. The current flowing through the battery to achieve the predetermined relationship is directly related to the internal impedance of the battery. A voltage related to the value of this current is then telemetered to the external receiving means. In a specific embodiment, the variable load is a field effect transistor (FET) connected as a source follower. The impedance of the FET is controlled by the output of an operational amplifier having as inputs the reference voltage and a voltage related to the output voltage of the battery. The monitoring means operates in a closed-loop servo system manner until the two input voltages to the operational amplifier are equal. The other terminal of the battery is connected to a shunting resistor. Thus the voltage drop across the shunting resistor is related to the current drawn from, and the internal impedance of, the battery. This voltage is telemetered to the external receiving means.

High transformation ratio for impedance matching with a radial line

Abstract: A description is given of impedance matching by means of radial lines mounted in a rectangular waveguide. It is shown that low-loss high-resistance transformation ratios of up to 1:300 are suited for matching active microwave semiconductor devices.

Impedance measurement using a 6-port directional coupler

Abstract: The development of a 6-port directional coupler is briefly described. Its application to a new technique of impedance measurement in which the magnitude and phase of the associated reflection coefficient are determined in terms of power measurements is shown. In contrast to a wellknown commercially-available network analyser the technique obviates the need for a complex heterodyne system. It is also potentially suitable for automatic wide-band impedance measurement.

Automatic, digitally synthesized matching line terminating impedance

Abstract: A circuit for automatically digitally synthesizing an output impedance, which may be a matching line terminating impedance, is provided The means for establishing the desired output impedance characteristic is accomplished using a simplified recursive digital filter arrangement In addition, means are provided for eliminating the effects of incidental undesirable shunting impedances

The impedance of the Leclanché cell. III. The impedance of the cell at different stages of discharge and state-of-charge indication by the impedance method

Abstract: The prediction of the residual capacity of some primary electrochemical storage cells has been investigated using the impedance technique over an extensive frequency range. The frequency responses of Leclanche cells in various states of charge are presented and it is shown that the gross changes in impedance which result from discharging provide an adequate parameter for state-of-charge prediction. The component factors of the whole-cell impedance have been investigated and the contributions of the various cell components to the resultant frequency-response (resistive and reactive) spectrum identified. A knowledge of these contributions is important for the development of a suitable device for the rapid testing of cell quality since in principle the examination of each mode of failure of each component demands a separate test. In practice the understanding of the frequency response of the cell has enabled us to construct a relatively simple instrument which gives an adequate estimate of cell condition for ordnance applications. A block schematic diagram is presented and the operation of the device is described in principle.

Circuit with feedback for controlling the impedance thereof

Abstract: An impedance control circuit with either current-controlled or voltage-controlled feedback loops in a transmission system. The impedance can be set at desired values, including complex values, and be different at different frequencies. The circuit is particularly useful in subscriber line interface circuits in telephone systems.

All digital LSI line circuit for analog lines

Abstract: A digital telecommunication line circuit implementable on one or more large scale integrated circuit (LSI) chips is described. A simplified integrated hardware structure is provided so as to achieve the combination on an LSI chip of an electronic two-to-four wire hybrid, line impedance matching by automatic digital impedance synthesizing of an output impedance and all digital filtering functions for an all LSI telephone line circuit including automatic equalizing.

Low power differential amplifier

Abstract: A differential amplifier (24, 26, 10 and 12) having a feedback network (30, 34, 32, 36 and 38) for increasing common output without loss of gain. Also disclosed is a constant current source (60), and a level shifting network (48, 50, 52 and 54) for shifting the D.C. level of the output signal to a D.C. voltage substantially near that of second current source (44). An output stage (84, 86, 90, 92 and 94) provides low output impedance, low D.C. bias power consumption and high current drive capability.

High-power ac voltage stabilizer

Abstract: An injection transformer has a primary winding series connected with a pair of inverse parallel-connected thyristors between a pair of input terminals. A control circuit is connected across a pair of output terminals for firing the thyristors. The injection transformer has a secondary winding connected between one of the input terminals and one of the output terminals for producing an injection voltage. A filter has components presenting a high impedance to the harmonic frequencies of the injection voltage and a low impedance to the fundamental frequency of the injection voltage, and has components presenting a high impedance to the fundamental frequency of the injection voltage and a low impedance to the harmonic frequencies of the injection voltage. The filter is connected such that the flow of current through the thyristors is limited, the harmonic frequencies are attenuated, and the fundamental frequency is added vectorially to an AC source voltage connectable at the input terminals thus providing a filtered, regulated, AC voltage across the output terminals.

An Adaptive-Control Switching Buck Regulator-Implementation, Analysis, and Design

Abstract: Describing-function techniques and averaging methods have been employed to characterize a multiloop switching buck regulator by three functionsl blocks: power stage, analog signal processor, and pulse modulator. The model is employed. to explore possible forms of pole-zero cancellation and the adaptive nature of the control to filter parameter changes. Analysis-based design guide lines are provided including a suggested additional RC-compensation loop to optimize regulator performances such as stability, audiosusceptibility, output impedance, and load transient response.

Impedance matching circuitry for radio frequency signal power amplifiers

Abstract: Impedance matching circuitry is described that utilizes a plurality of series coupled microstrip transmission lines of different characteristic impedances for matching a radio frequency (RF) signal power amplifier to a predetermined output impedance, such as, for example, 50 ohms. Each of the microstrip transmission lines are successively coupled to the relatively low impedance output of a transistor of the power amplifier that is desired to be matched to the predetermined output impedance. Each of the successively coupled microstrip transmission lines has a greater characteristic impedance than the previously coupled microstrip transmission line for achieving the desired impedance match. The series coupled microstrip transmission lines not only match the power amplifier transistor to the predetermined output impedance, but also suppress regenerative oscillations which may occur when the power amplifier transistor is subjected to impedance mismatches. The inventive impedance matching circuitry may be advantageously utilized in the RF signal power amplifier of a base station radio in a mobile radio communication system.

Arrangement for the generation of a signal in proportion to a capacity

Abstract: An active measuring converter for connection between a two-wire line and an impedance to be measured, wherein an oscillator supplies alternating voltage to the impedance, and the variation in current drawn by the oscillator is in accordance with the value of the impedance. The measurement signal is transmitted together with the power for the active measuring converter via a two-wire line. The oscillator supplies the impedance with stabilized AC voltage independent of its operating current. Electronic switching devices coupled to the impedance either add the alternating current to the measuring signal as an impressed current, or couple it to a resistor-capacitor network for establishing a reference input for the controlled variable voltage. The alternate coupling of the alternating current corresponds to the alternating polarity of the AC current flowing through the impedance. The impedance may be the capacitance of a sonde which varies according to filling level. The converter draws a minimum of current and may be adjusted for any given measurement conditions.

Line hold circuits

Abstract: OF THE DISCLOSURE A single line hold circuit adapted for connection between the tip and ring leads of a telephone line. The circuit comprises variable impedance devices for connection between the tip and ring leads, the impedance devices including a semiconductor element having high and low impedance states, the impedance of the low impedance state being sufficiently small to maintain the telephone line in a hold condition. The circuit further causes the semiconductor to be in its low impedance state following an interruption of a predetermined length of time in loop current. A double line hold circuit is also illustrated.

Pulse modulated IMPATT diode modulator

Abstract: A high efficiency modulator circuit for modulating a microwave oscillator having a negative resistance device comprising an IMPATT diode disposed within a resonant cavity is presented. A first transistor comprising a relatively high output impedance, fast transient response, low power dissipation, wideband current source modulates the power applied to the diode thereby reducing power dissipation and improving the power conversion efficiency of the modulator during operation. Current controlling and limiting means is provided in the emitter of the first transistor for controlling and limiting the current to the diode for improving the burn-out reliability thereof. A modulating signal is provided to the base of the first transistor by the emitter of a second transistor connected in a modified Darlington configuration for providing a high efficiency, wideband, low impedance source to the base of the first transistor improving the transient response thereof. Adjustable feedback is provided around the two transistors for tailoring the source impedance and characteristics of the modulator to the particular diode thereby further improving the power conversion efficiency, stability, and transient response of the modulator circuit.

Power source with an electronic impedance changer

Abstract: A circuit arrangement to provide a fixed voltage source in series with an arbitrarily chosen impedance of any magnitude and phase shift having very low power dissipation and capable of being fabricated on silicon integrated chips is disclosed. The circuit arrangement includes a sensing resistor to sense the output current of a power converter which is amplified and fed back with an appropriate phase shift to control the output voltage of the converter. An independent control signal may be combined with the fed back voltage to change the chosen impedance to another type of impedance.

Input optimized FET bias circuit

Abstract: A field effect transistor bias circuit is presented which exhibits a low impedance for small signals and a high impedance for large signals. This circuit uses an operational amplifier to provide a temperature compensated low impedance voltage source for the gate bias which is optimal for small signal operation. In the presence of a large signal, the gate begins to draw current. This causes the operational amplifier to saturate and transforms the bias circuit into a high impedance source, which is optimal for large signal operation.

Impedance generator circuit

Abstract: An improved impedance generator circuit, for use with two-wire transmission systems of the type encountered in telephony, is adapted to be interfaced with the wires and operates in a manner to effectively generate a desired positive or negative impedance across the wires. The impedance generator includes a current source, and generates a positive impedance by drawing from the wires all of the current that would otherwise be required by the positive impedance, or a negative impedance by providing on the wires all of the current that would otherwise be provided by the negative impedance, in response to a metallic voltage applied across the wires by a signal source. At the same time, the impedance generator provides common mode rejection to longitudinal voltages on the wires.

Impedance canceller circuit

Abstract: An improved impedance canceller circuit, for use with two-wire transmission systems of the type encountered in telephony, is adapted to be interfaced with the wires and operates in a manner to effectively eliminate or cancel an unwanted impedance across the wires. The impedance canceller includes a current source, and essentially supplies on the wires all of the current that would otherwise be required by the unwanted impedance in response to a metallic voltage applied across the wires by a signal source, so that the signal source does not supply such current and the unwanted impedance appears as an open circuit to the metallic voltage. At the same time, the impedance canceller provides common mode rejection to longitudinal voltages on the wires.

Magnetic recording system with signal-controlled bias and equalization

Abstract: A stereophonic magnetic tape recording system having a pair of magnetic recording heads each provided with its own signal processing circuit including amplifiers, an equalizer, etc. Shared by both channels, a bias oscillator feeds a bias current, having a frequency higher than the spectrum of the information signals to be recorded, to both record heads. For continuously adapting the recording bias and equalization to the high frequency portions of the information signals, each channel is further provided with a variable impedance circuit connected in parallel with one of the record heads, and a control circuit for varying the impedance of the variable impedance circuit as dictated by the high frequency portion of the corresponding information signal. A decrease in the impedance of each variable impedance circuit results in the reduction of the bias current fed to the corresponding recording head and of the high frequency level of the information signal; conversely, an increase in the impedance of the variable impedance circuit results in an increase in the bias current and in the high frequency level of the information signal.

Multipurpose test equipment input circuitry

Abstract: An input terminal adapted to receive 0 to 300 volts AC or DC is connected through AC or DC connecting circuits, coupled into the path by switches, and attenuating apparatus including a plurality of ranges automatically switched into the path in response to the amplitude of an input signal, to a buffer which includes overvoltage protection and provides a relatively high input impedance with a relatively low output or source impedance. A frequency counter is connected through a hysteresis amplifier, a digital volt meter is connected through an amplifier including 60 cycle filtering and an oscilloscope is connected through an independent gain amplifier to the output of the buffer.

L-C Filter with impedance transformers

Abstract: Input signals having a particular impedance in a particular frequency range are provided. A first transformer has at its input a particular impedance in the particular frequency range and provides a change at its output to a second impedance in the particular frequency range. A filter is constructed to receive the signals from the first transformer and is provided with the second impedance in the particular frequency range. When the second impedance is lower than the particular impedance, the operation of the filter at the second impedance is advantageous because the size of the inductances in the filter is significantly reduced without impairing the quality of the inductances or increasing energy losses in the inductances. A second transformer is constructed to receive the signals from the filter. The second transformer provides the second impedance at its input and provides at its output a change to the particular impedance in the particular frequency range. Means are connected to the second transformer for providing output signals having the particular impedance in the particular frequency range.

High speed AC/DC coupler

Abstract: A high speed AC/DC coupler has an optical circuit for DC coupling and an AC coupler circuit, both receiving a digital input signal and both providing outputs resulting from the input signal to the same point of a clipper circuit. The response characteristic of the AC coupler circuit is faster than that of the optical coupler circuit and the output impedance of the optical coupler circuit is of such a magnitude to permit the output of the AC coupler to overdrive the output of the optical coupler. The time constant of the AC coupler circuit is set so that the signal from the AC coupler is impressed on the clipper circuit and remains impressed at least until the slower optical coupler output is also applied to the clipper circuit. The circuit provides a faithful reproduction of essentially any length input pulse, delayed a minimal time.

Two to four wire hybrid circuit

Abstract: There is disclosed a two- to four-wire hybrid circuit of a telecommunication system. A line coupling circuit, preferably a transformer is connected to a terminal line. Between the coupling circuit and first and second amplifying means each assigned to a receiving branch and a transmitting branch of a transmission line, respectively there is arranged a balancing network composed of an attenuator, a first and a second hybrid impedance. The first impedance connected to the coupling circuit has a value matching the value of a coupled terminal line impedance which is effective at the four-wire side of the coupling circuit. The second impedance and the attenuator interconnect the outputs of the first amplifying means. The value of the series connection are chosen such that the resistance value of the attenuator is substantially higher than the value of the actual resistance component of the first impedance and the ratio of the coupled line impedance to the first line impedance equals the ratio of the attenuator resistance to the second impedance. The second input of the second amplifying means is connected to the coupling circuit.

Regulated power supply with loss compensation

Abstract: An inverter power supply circuit (10,12) compensates for variations in the power supply's output voltage (vout) which are due to variations in output loading. The input side of the circuit's coupling transformer (T.) incorporates a current sensing network (14) 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 (Rout) and the current sensing network (14). The changing current in the current sensing network (14) on the input side of the coupling transformer (T 1 ) generates a corresponding changing voltage that is coupled, as a positive feedback, to a chopping transistor (Q 1 ) of the power supply to provide compensation for changing losses following variations in loading on the output side of the coupling transformer (T 1 ), without the need for a feedback connection from the output circuit.

Telephone line circuit

Abstract: The line circuit comprises at least a driver stage 1 having an amplifier. This amplifier is provided with a feedback circuit for forming a virtual output impedance which functions as a supply resistor so that additional collector space is created for the amplifier output transistor. In addition, the line circuit comprises a controlled supply source 5 connected to the amplifier output transistor for eliminating this additional collector space, which results in a low-dissipation line circuit.

Voltage-to-current converter circuit

Abstract: A voltage-to-current converter circuit comprises first and second amplifiers each having a noninverting input, an inverting input and an output, the noninverting inputs of the first and second amplifiers being respectively connected to an input terminal for receiving an input signal and circuit ground, a first impedance element connected between the inverting input of the first amplifier and circuit ground, a second impedance element connected between the output and the inverting input of the first amplifier, a third impedance element connected between the output of the i first amplifier and an output terminal to be connected to a load, a fourth impedance element connected between the inverting input of the second amplifier and the output terminal, a fifth impedance element connected between the output and the inverting input of the second amplifier, and a sixth impedance element connected between the output of second amplifier and the inverting input of first amplifier. When the second to sixth impedance elements are selected to have respective impedance values Z 2 to Z 6 which satisfy an equation ##EQU1## the voltage-to-current converter circuit operates as a constant current amplifier which is capable of supplying the load with an output current signal of a constant amplitude when the input signal voltage is constant, regardless of the impedance value of the load.