Showing papers on "Output impedance published in 1982"

Electrodeless light source

Abstract: A termination fixture for an electrodeless lamp has dimensions which match the output impedance of a coupled high frequency power source to the real impedance of the lamp when in a discharge condition. The fixture may consist of a pair of coaxial conductors, and the lamp forms the termination load for the ends of the conductors. The length of the conductors is such as to place the lamp one quarter wavelength from the opposite ends of the conductors. The diameters of the conductors are such as to produce a fixture characteristic impedance which matches the lamp impedance to the source output impedance.

Bistability and negative resistance in semiconductor lasers

Abstract: Experimental results of a buried heterostructure laser with a segmented contact to achieve inhomogeneous gain are presented. Measurements reveal a negative differential resistance over the absorbing section. Depending on the source impedance of the dc current source driving the absorbing section, this negative resistance can lead to (i) bistability with a very large hysteresis in the light-current characteristic without self-pulsation or (ii) a small hysteresis with self-pulsations at microwave frequencies. An analysis, which includes the electrical part of the device, leads to an explanation of self-pulsations in inhomogeneously pumped lasers without having to rely on a sublinear gain dependence on injected carrier concentration.

MOS Current mirror with high impedance output

Abstract: An improved MOS current mirror wherein the mirror transistors are biased to operate in the saturated region near the boundary between the linear and the saturated regions to maximize the voltage gain and the power supply rejection ratio while maintaining a high output impedance.

Electrosurgical generator with improved rapid start capability

Abstract: An electrosurgical generator, having particular utility in arthroscopic surgical procedures, is provided with a rapid start capability in its pure cut mode by inhibiting secondary modulation for an initial starting interval during which an uninterrupted high frequency cutting signal is applied to the output terminals. Upon expiration of the starting interval, the secondary modulation takes effect to modulate the cutting signal with a low frequency repetitive signal having a predetermined duty cycle. In addition, the generator output isolation transformer is arranged to provide an output impedance of at least 1,000 Ohms to match the impedance of human joints on which arthroscopic surgery is performed.

Dynamic output impedance for 3-state drivers

Abstract: This describes a tristate driver circuit designed such that it will not be destroyed by excessive high voltage conditions when two such drivers are connected to a bus at the same time. The circuit accomplishes this with parallel high current, low impedance and low current, high impedance output devices, coupled to means for causing the high current, low impedance devices to supply, to the circuit output, only the initial high currents required without inhibiting the low current, high impedance devices from maintaining the steady state conditions needed to clamp the output at the desired output level. The circuit is arranged to cause both high and low current output devices to be initially conductive to charge the output terminal to the desired level, but to subsequently shut off the high current, low impedance device while keeping the low current, high impedance device in a condition to clamp the output at the desired level. This result is achieved by providing the high current output devices with means for automatically terminating once the initially required high current has been supplied to the output.

Microprocessor controlled thermocouple simulator system

Abstract: A thermocouple simulator system which is capable of generating a voltage equivalent to the EMF output of a thermocouple of a selected type at a specified sensing junction temperature. The system includes a keyboard which allows an operator to specify a sensing junction temperature, voltage, thermocouple type, reference junction temperature, and whether a pair of output terminals of the system perform as thermocouple alloy or copper. Using an operation program, a microprocessor calculates the thermocouple EMF using a stored temperature versus EMF polynomial function of the selected thermocouple type. The microprocessor then causes a voltage simulating the calculated EMF to be applied to the output terminals utilizing a reference voltage source, digital-to-analog converter (DAC), and output amplifier. When the wires connected to the output terminals are made of a different metal than the terminals, signals from temperature sensors in the output terminals are fed to the microprocessor through an analog-to-digital converter. The microprocessor then offsets the voltage simulating the EMF output to compensate for the thermocouple junction formed in connecting the wires to the output terminals. The system may also operate as a precision DC power supply with extremely low output impedance.

Device for detecting the variation of a capacitive impedance having dielectric consisting of a lubricant

Abstract: The invention relates to a device for measuring the variation of a capacitive impedance, the dielectric of which consists of a lubricant, provided with an oscillator that supplies a signal having a predetermined frequency to the capacitive impedance by way of a bias impedance. The device according to the invention is characterized by a current measuring means delivering a signal depending on the current passing through the capacitive impedance to a converter the output of which delivers a direct current voltage signal coinciding with the instantaneous value of the capacitive impedance.

Device for measuring the variation of a capacitive impedance, the dielectric of which consists of a lubricant

Abstract: Device for measuring the variation of a capacitive impedance the dielectricum of which is formed by a lubricant. The device comprises an oscillator (1) providing a constant frequency signal through a capacitor impedance (2). A currant measuring means preferably a current transformer (3, 4, 5) provides a signal depending on the current flowing through the capacitive impedance (2). This signal is converted into a DC signal by means of a bandpass-filter (6) and a simpel diode detector circuit. The DC signal corresponds to the momentary value of the capacitive impedance (2). Due to this method the quality of the lubricant e.g. in a bearing can be measured with a relatively cheap device.

An impedance measurement method for double-gap klystron cavity

Abstract: A new method has been developed for measuring the impedance of a two-gap cavity used in high-power klystrons. The principle is based on network analysis. The cavity under test is considered as a microwave network. The two gaps of the cavity and its output terminal are referred to as three ports. We then can use an impedance matrix to characterize this system, and the six independent impedance parameters can be found by measuring the input impedance seen from the output waveguide when the gaps are in different conditions; viz., either open, shorted, or perturbed. The gap impedance then can be deduced therefrom. It is shown that there are three impedances for a double-gap cavity instead of one for a single-gap cavity. Another problem dealt with here is how to evaluate the capacitance introduced by the perturbation. A few typical experimental results are presented.

Notch antenna for a wide frequency band

Abstract: Notch antennae consist either of a cut in a metallic structure or of an electrically conductive frame on a metallic body, and of a tuning capability to a specific frequency. This is implemented according to the invention in that the connecting cable is connected at the one end to the notch antenna, i.e. in the region of the open end in the case of a cut, and at its one end in the case of a frame. Connected in parallel with the connecting cable is a capacitor whose value is changed as a function of the frequency band in order to compensate for the reactive components of the antenna internal impedance. In the region of the opposite end, i.e. in the inner part in the case of a cut and at the opposite end in the case of a frame, a terminating reactance is inserted whose value is likewise changed as a function of frequency such that the resistive components of the antenna internal impedance has the desired magnitude. The latter may consist of the parallel connection of variable capacitances and a connected inductor. The capacitances are formed by capacitors which can be connected in parallel and can be switched, for example, by PIN diodes.

A Programmable Load for Power and Noise Characterization

Abstract: A digitally-controlled one-port tuner, providing sixty-four distinct impedances, has been used to examine the relationship between nonlinear power transistor performance and load impedance. In a similar way, the noise parameters of low noise linear transistors have been deduced from measurements using the tuner to control source impedance. All control, measurement and data reduction functions are performed with a desktop computer.

Air conditioning thermostatic control system having modular inclusion of remote temperature set-back capability

Abstract: Methods and circuits for providing auxiliary or remote temperature set or set-back capability in comparator-based thermostatic temperature control systems. In particular, the invention is applicable to thermostatic control systems of the general type including a temperature-responsive source for producing a temperature-dependent voltage as a function of sensed temperature, a reference voltage source for establishing a temperature set point, a voltage comparator having a comparison input and a reference input for producing a control output signal for energizing a thermal conditioning element when voltages applied respectively to the comparison and reference inputs have at least a predetermined relationship with respect to each other, an electrical connection between said temperature-responsive voltage source and the comparison input, and an electrical connection between the reference voltage source and the reference input. For remote temperature setting, the set point voltage applied to the comparator reference input is forced towards a particular value representative of a particular temperature by employing an auxiliary reference voltage source having an output impedance lower than that of the reference voltage source. Preferably, the auxiliary reference voltage source includes, as an output element, a unity-gain operational amplifier.

Power amplifying circuit

Abstract: PURPOSE:To reduce the impedance of the screen grid of an electron tube, by interposing a transistor (TR) and a bias resistance between the screen grid and two bias resistances determining the bias value of the screen grid CONSTITUTION:Between two bias resistances 2 and 3, determining the bias voltage of the screen grid 11 of an electron tube, and the screen grid 11, a TR7 and a bias resistance 8 are interposed Thus, the input impedance of a TR circuit 14 is increased exteremely and the output impedance is decreased extremely, so that impedance of the screen grid 11 is decreased to suppress low the variations of the bias voltage of the screen grid 11

DC Motor control circuit

Abstract: A DC motor control circuit for controlling the speed and direction of rotation including a plurality of linear amplifiers which are, respectively, connected to each of the stator windings of the DC motor and a pulse generator for generating rotational pulse trains which represent the rotational phases of the rotor of the DC motor and output impedance control pulse generator for generating based on the rotational pulse train control pulses which selectively control the linear amplifiers so as to produce nearly infinite output impedance and a motor control voltage and signal inverter for inverting the motor control voltage and a plurality of switching circuits connected to the inputs of the linear amplifiers for supplying the motor control voltage and phase inverter motor control voltage in a selective manner to each of the linear amplifiers and switching circuit control pulse generator for generating switching pulses based on the rotational pulse trains which are supplied to each of the switching circuits.

A general theory of broadband matching of an active load

Abstract: Given a passive frequency-dependent source impedance and an active or passive load and a preassigned transducer power-gain characteristic, necessary and sufficient conditions are given for the existence of a lossless reciprocal equalizer which, when operating between the given source and the given load, yields the desired transducer power-gain characteristic. The significance of the present approach is that the realization of the equalizer involves only driving-point synthesis by the Darlington theory.

Method and apparatus for time based measurement of impedance

Abstract: Method and apparatus for time lapse based measurement of impedance wherein a series of time measurements are made by voltage transitions with respect to a reference voltage across an unknown component and across a reference component with a known impedance. The time measurements are fed to a microprocessor or other computer means for calculating the impedance of the unknown component.

Electronic impedance device for providing a variable impedance

Abstract: An electronic impedance device provides a variable impedance in, for example, a Dolby noise reduction system. The device includes an input terminal connected to a source of a signal voltage. A differential voltage-to-current converter circuit, having a relatively high input impedance, converts the input signal voltage into two differential output currents that are variable with the input signal voltage. A pair of p-n junction elements, such as diodes, are connected to the converter circuit via a current transfer circuit. The current transfer circuit transfers the differential output currents to the p-n junction elements. A differential current amplifier circuit is responsive to the voltage built up across the p-n junction elements. The differential current amplifier has an output terminal to produce an output current. A feedback line connects the output terminal of the amplifier circuit to the input terminal for permitting the output current of the amplifier circuit to be fed back to the input terminal of the device.

High frequency switching inverter

Abstract: PURPOSE:To contrive to reduce distortion of wave form of output and to reduce output impedance of a high-frequency switching inverter by a method wherein a part of output of the inverter is fed back to an amplifying circuit through a feed back circuit CONSTITUTION:Signals obtained by performing amplitude modulatin in an amplitude modulating circuit 15 on a sine wave sent from a sine wave generating circuit 14, and triangular waves or saw tooth waves sent from a triangular wave or saw tooth wave generating circuit 19 are performed with phase modulation respectively in comparators 20a, 20b, a switching circuit 2 is made to perform switching by the output signals of the comparators to obtain higher harmonic signals, and moreover the signals thereof are demodulated in a demodulating circuit 8 by synchronizing rectification making synchronizing signals sent from a frequency dividing circuit 13 as the reference to convert into the sine wave and to obtain the output of the inverter A part of the output of the inverter is fed back to the amplifying circuit 18 through the feedback circuit 21 Accordingly because distortion of wave form of the AC output is improved and output impedance is reduced, transient characteristic to be generated by fluctuation of load can be improved

Analysis of Distribution Power-Line Carrier Propagation by Transfer Impedance

Abstract: Distribution power-line carrier is used to provide two-way communications for full function load management systems. Because of the low impedance of the distribution lines, and the fact that the impedance changes with the line load, any attempt to match the transmitter and receiver to a characteristic impedance would be impractical.

Envelope detection circuit

Abstract: PURPOSE:To decrease the voltage loss and to realize a low voltage operation, by providing an emitter common amplifying curcuit at an output terminal of a feedback amplifying circuit and smoothing the output of the emitter common amplifying circuit as an output and feeding it back. CONSTITUTION:An input signal is amplified with inversion at an operational amplifier 9 and inputted to a base of a common emitter amplifying circuit 13. An output picked up with a low impedance from the collector is outputted via a smoothing circuit 7 and fed back from the collector to the operational amplifier 9 via a transistor (TR) 17. A TR13 is conductive when the potential of an input terminal is positive and is cut off when negative. When the TR13 is conductive, charging is made to the smoothing circuit 17 and a voltage corresponding to the input voltage is obtained at a terminal 10. Since the output impedance of the TR13 is low, the charging time constat is dependent on a resistor 14.

Microwave impedance measurement apparatus

Abstract: Apparatus for measuring the impedance or another parameter of a device by reference to the standing wave pattern set up in a transmission line along which microwave energy is applied to the device. A section of the transmission line has three spaced probes from the output voltages of which corresponding digital values are produced and digital computing means calculates the impedance from the values. Calibrating measurements using a matched load and a short circuit instead of the device are performed earlier and the result representing probe sensitivities and energy wavelength used to simplify and speed up the calculations, so that a reasonably smooth display plot of the impedance with varying energy frequency can be produced in real time. The computing means has an 8-bit microprocessor for the handling and a 16-bit microprocessor to perform the calculations.

DC-DC converter with an inductive store

Abstract: A DC-DC converter with an inductive store, with a charging capacitor and with a constant-current regulator for regulating the current emitted by the output circuit to a load. In such a DC-DC converter it is intended to ensure that, without any adverse effect on the stability of the control loop, a load which is additionally connected to the output has as little effect as possible on the accuracy of the current regulation. To this end, the invention provides that the desired value output of the actual value/desired value comparator is passed via a resistor to the connection of the charging capacitor facing the actual value transmitter and that the internal impedance of the desired value transmitter has a value other than zero.

Switching circuit which is self-biased in one mode of operation

Abstract: Each of a plurality of circuit paths between a common input terminal and respective output terminals includes a switching device which can be switched between a high and a low impedance state. When a device in one path is switched into its low impedance state in response to a path selection signal, the devices in the remaining paths automatically are switched to their high impedance state in response to a portion of the signal to be passed through the path with the low impedance device. In this way, one of the circuit paths may be selected for coupling the input terminal to a selected output terminal and all other circuit paths are automatically blocked.

Termination for high impedance attenuator

Abstract: A termination for high impedance attenuator to be connected to the input of such high impedance attenuator. The termination circuit includes a series combination of a termination resistor, a delay line and an inductor, thereby cancelling the negative reflection due to the capacitive element at the output of the attenuator while maintaining the overall input impedance constant over a wide frequency range.

Contour correction signal composite circuit of video signal

Abstract: PURPOSE:To form a contour correcting circuit of a video signal, whose phase characteristic is excellent, by use of a few number of parts, by providing a reflecting circuit on the output side of a delaying circuit. CONSTITUTION:When an input signal 16 as shown by a full line in the figure (a) is inputted to an input terminal 15, this signal passes through a delaying circuit 9 and reaches a reflecting circuit 11. In this case, the reflecting circuit 11 has the impedance of a mismatching value to the output impedance of delaying circuit 9, the greater part or a part of the signal is reflected. This reflected signal is returned to a terminal 17 through the delaying circuit 9 once again, and a reflected signal 18 which has been delayed by 2Td is compounded with the previous input signal [a full line in the figure (b)]. Moreover, when this composite signal 19 and an output signal 20 of he delaying circuit 9 are subtraction-processed in a compounding circuit 10, a contour correction signal 22 as shown in the figure (c) is obtained by an output terminal 21.

A programmable power processor for high power space applications

Abstract: A Programmable Power Processor (P3) has been developed by NASA/Marshall Space Flight Center for application in future large space power systems. The P3 is capable of operation over a wide range of input voltage (26 to 375 Vdc) and output voltage (24 to 180 Vdc). The peak output power capability is 18 kW (180 V at 100 A). The output characteristics of the P3 can be programmed to any voltage and/or current level within the limits of the processor and may be controlled as a function of internal or external parameters. Seven breadboard P3s and one "flight-type" engineering model P3 have been built and tested both individually and in electrical power systems. The programmable feature allows the P^ to be used in a variety of applications by changing the output characteristics. The tests have been performed for four potential applications, a high voltage battery peak power tracking charger, a 120-V bus regulator, a 30-V bus regulator, and a peak power tracking impedance matching regulator. Test results, including efficiency at various input/output combinations, transient response, and output impedance, are presented. Packaging considerations for the 18 kW are also discussed.

Hall motor controlling circuit

Abstract: PURPOSE:To obtain a simple Hall motor controlling circuit by providing the first conductive type differential transistors inputting the output of Hall elements and the second conductive type transistors receiving the outputs of the first transistors and outputting from the collectors to a constant current load provided in the collector circuits. CONSTITUTION:A rotary position detection signal from a Hall element H is inputted to differential transistors Q1, Q2 in a Hall amplifier A1. A differential amplification signal obtained from the collector of the Q7 in a current mirror circuit having transistors Q6, Q7 and resistors R6, R7 is inputted to the amplifying stages of transistors Q9, Q10. The voltage gain of the amplifier A1 is set by the feedback circuit of resistors R2, R3. The output impedance becomes large by a constant current circuit of resistor R5 connected to the collector of Q9, Q10 and the transistor Q4. The output current of the amplifier A1 is amplified through a drive circuit A2 to drive a stator coil and to limit the amplitude via the transistor Q5.

Measured Transfer Impedance of Braid and Convoluted Shields

Abstract: The surface transfer impedance of 36 samples of cable shields were measured from 1 kHz to 100 MHz. Measurements were made in 1 and 6 meter long quad­ raxial test fixtures using computer controlled net­ work analyzers. The apparatus was calibrated using shields made from copper pipes, having a known resis­ tance and leakage mutual inductance. These calibra­ tion shields also allowed the noise floor of the system to be measured. The cable shield samples included tubular and machine braids, magnetic and non-magnetic convolutes, tape wound aluminum and stainless steel conduits, metal tapes and combina­ tions. All samples used a 3/4" diameter core made up of 19 shielded twisted pairs. The convolute and conduit samples were 1-1/4" in diameter.