Showing papers on "Negative impedance converter published in 1987"

Frequency feedback on a current loop of a current-to-pressure converter

Abstract: A current-to-pressure (I/P) converter (20) provides an output pressure as a function of the magnitude of a variable input DC current. The I/P converter (20) includes a pressure sensor (64) which produces a feedback signal representative of the output pressure. Based upon the feedback signal and the magnitude of the input DC current, an electrical control signal is produced which controls a device (40) for varying the output pressure. The I/P converter (20) also includes a circuit (86) for generating a time-varying signal which is sent back over the current loop wires (28) through which the input DC current flows. The time-varying signal provides an indication of whether the I/P converter (20) is functioning properly. This permits diagnosis of possible causes of control system malfunctions without having to inspect the I/P converter (20) itself.

Method and apparatus for warning of disconnection of an appliance from a power source

Abstract: In the method of the invention, a signal is injected into the power cord of an appliance and a reference voltage is set in response corresponding to a reference impedance at the point of signal injection. The reference impedance is present with the appliance connected to the power source. The reference voltage is continuously compared against a present voltage corresponding to present impedance at the point of signal injection. An alarm sounds if the present voltage changes to exceed the reference voltage, indicating a higher impedance because the appliance has been disconnected. In one embodiment, the apparatus includes an impedance bridge having an adjustable reference arm for producing a reference voltage corresponding to the impedance of the cord and appliance and a sensing arm for producing the present voltage. In a second embodiment, the apparatus injects an adjustable current into the power cord and appliance for a predetermined time to provide a present voltage. The present voltage is then compared against a reference voltage. The third embodiment is designed for mounting within the chassis of an appliance. The current is injected into the power cord and power source for a predetermined time to produce the present voltage for comparison against a reference voltage.

FET voltage reference circuit with threshold voltage compensation

Abstract: A voltage converting circuit has an output MIS transistor which gives a low output impedance and outputs an intermediate level of power source voltage. The output level is set with a high accuracy through a voltage dividing ratio determined by an impedance element. This impedance element is connected with a compensating MIS transistor to compensate for variations of the gate threshold voltage caused by the manufacturing process.

Electronic load for testing transformers

Abstract: An adjustable electronic load for testing current transformers and/or voltage transformers, the load having connected, between its input current terminals, a series connection including the input of a current-to-voltage converter and the output of a controlled generator, and having connected, between its input voltage terminals, the input of a voltage-to-voltage converter. The outputs of the current-to-voltage converter and the voltage-to-voltage converter are each connected via an impedance to a control input of the controlled generator. The voltage-to-voltage converter and the current-to-voltage converter each comprise at least one amplifier with adjustable amplification. The amplifications of the two adjustable amplifiers are adjustable jointly in opposite directions. In the case of a load for testing a current transformer, with the rated secondary power of the current transformer being predetermined, the amplification of the current-to-voltage converter is reduced or increased and the amplification of the voltage-to-voltage converter is increased or reduced respectively, so as to increase or reduce the rated secondary current, respectively. In the case of a load for testing a voltage transformer, with the rated secondary power of the voltage transformer being predetermined, the amplification of the voltage-to-voltage converter is reduced or increased and the amplification of the current-to-voltage converter is increased or reduced respectively, so as to increase or reduce the rated secondary voltage, respectively.

Differential impedance neutralization circuit

Abstract: An impedance neutralization circuit produces correction currents to compensate for the effects of parasitic impedance on the output voltage of an amplifier. In the described embodiment, the neutralization circuit includes a pair of emitter followers, one coupled to the collector of each transistor of a common base amplifier for sensing the output voltage at each collector. A pair of transistors are coupled one to each emitter follower for applying the sensed voltage across a neutralizing impedance proportional to the parasitic impedance seen at the collector of the opposite transistor of the common base amplifier. The voltage applied across the neutralizing impedances produces a correction current. The correction current is summed with a distortion current of proportional amount but opposite sign produced by the output voltage applied across the parasitic impedance to produce a substantially error-free output voltage.

DC to DC converter with overvoltage protection circuit

Abstract: An overvoltage protection circuit limits the output voltage of a DC to DC converter to a maximum desired output voltage. An output voltage sensing circuit includes a semiconductor device such as a sidac having a normal resistive region of operation as well as a negative resistance region of operation which begins at a breakover voltage and extends into a foldback region. One terminal of the sidac is coupled to sense the converter output voltage while the second terminal opposite end of the sidac is coupled to a biasing device in the form of a resistor which generates an overvoltage signal when the sidac conducts current. The overvoltage signal from the biasing resistor is coupled to a converter switching transistor disabling circuit which reduces the converter output voltage to a level below the maximum desired output voltage in response to the overvoltage signal.

Voltage to current converters for use in an active filter and with a moise reduction circuit

Abstract: The invention relates to a voltage to current converter suited for integration. The voltage to current converter combines the outputs of two voltage to current converting circuits whose operating input levels are different from each other so as to prevent the generation of direct current offset voltage. The voltage to current converter is suitable for the construction of a filtering circuit.

Fiber optic receiver

Abstract: An optical receiver especially useful for digital fiber optic systems operating a high pulse rates, converts the pulsed current signal generated by a PIN diode into a pulsed voltage utilizing a current to voltage converter comprising an FET input transistor, a complimentary cascoded bipolar transistor, and a large feedback resistor to reduce noise while providing a wide band width and dynamic range. The pulsed voltage signal is amplitude limited in a limiting amplifier and passed through a low pass filter to remove excess bandwidth and further reduced noise before being applied to a high speed comparator which generates the digital output. The pulsed voltage signal is passed from the current to voltage converter to the limiting amplifier through an emitter follower coupling transistor to isolate the open loop gain of the current to voltage converter so that its band width will not be changed with load.

Current-type converter protecting apparatus

Abstract: In a current-type converter system in which a DC current is fed to a load through a pulsating current suppressing DC reactor from a current-type converter constituted by self-extinction elements connected in a bridge circuit, a converter protection apparatus is arranged such that when a fact that a terminal voltage of the DC reactor becomes an overvoltage is detected, the self-extinction elements are turned on so as to form a closed circuit including the DC reactor, the load, and the converter so that the overvoltage can be suppressed and continuous operation of the converter can be carried out.

Instrument for measuring the impedance, specially for determining the change of the impedance of a capacitive sensor by dipping in a fluid

Abstract: The impedance measuring instrument has as signal source a digital sinewave generator (12) which feeds the object to be measured (13). The zero transitions of current and voltage at the object to be measured (13) are detected by means of zero-transition detectors (16, 17) and a start-stop counter (11b) is operated by this means. The output signal of the latter is a measure of the time interval between the zero transitions from which the phase shift between current and voltage at the object to be measured (13) can be calculated with the aid of the known signal frequency of the digital sinewave generator (12). The equivalent resistance of the object to be measured (13) is measured, preferably directly, with the aid of an analog/digital converter (11a) and the quotient of the measurement values is formed. From this quotient and from the phase shift determined, the impedance is finally calculated. The analysing circuit contains a microprocessor (11) as central element which is synchronised with the digital sinewave generator (12) by means of a common clock.

Circuit arrangement for operating a high-pressure descharge lamp

Abstract: The invention relates to a circuit arrangement for operating a discharge lamp (1) by means of a direct voltage source, which circuit arrangement is provided with - direct voltage terminals (A,B) for connection of the di­rect voltage source, - alternating voltage output terminals (K,L) for connection of the discharge lamp, - a direct voltage/alternating voltage converter (3), and - a current limiter (5) for limiting the current through the lamp during the operating condition. According to the invention, the direct voltage/­alternating voltage converter (3) is a sine converter and a controllable direct voltage converter (2) is arranged between the sine converter and the direct voltage input terminals (A,B).

Pulse forming networks

Abstract: In a pulse forming electrical circuit (1) suitable for use with a gas discharge laser having continuously falling impedance, there is provided a saturable inductor (3) operable to cause the output impedance of the circuitry to vary with the current drawn by the load (2) thereby ensuring that the matching between the impedance of the circuitry and the load to be better than would be the case if the impedance of the circuitry were fixed.

Distortion reduction circuit for a D/A converter

Abstract: A distortion reduction circuit for a digital to analog converter, comprising a bit detection circuit for detecting the logic value of any bit from input data thereto, a synchronizing circuit for synchronizing the output from the bit detection circuit with the analog output from the converter, and an adding and subtracting circuit for converting the value of an output voltage from the synchronizing circuit to a direct current voltage having any level. The output from the adding and subtracting circuit is arranged to be added to the analog output from the digital to analog converter.

Voltage regulator having a precision thermal current source

Abstract: A voltage supply circuit for supplying a regulated output voltage the magnitude and temperature coefficient of which can be independently controlled. A pair of transistors and associated circuitry develop a voltage proportional to the V BE of the two transistors which are operated at different current densities and sets a first current through the collector of a third transistor which is proportional to V BE having a positive temperature coefficient (TC). A second current proportional to the negative temperature coefficient base-to-emitter voltage of the third transistor is generated and combined with the first current to produce a third current having a net negative, zero or positive TC. The third current is used to develop a voltage which is combined with the base-to-emitter voltage of the third transistor to produce the output voltage.

Actuator drive circuit

Abstract: An actuator drive circuit for driving a load using a single power supply. The current drive is not dependent on load impedance characteristics. Drive means provides a voltage across the first terminal and the second terminal during at input signal positive phase, and reverse voltage across the first terminal and the second terminal during a negative phase. A current detection resistor is connected in series with the load, and the voltage across the resistor is input to a differential amplifier. The amplifier output provides feedback to the drive means.

Method and apparatus for controlling circulating-current type cycloconverter

Abstract: A current-circulating cycloconverter includes a positive converter and a negative converter connected in anti-parallel with each other through a DC reactor. A load is connected to an intermediate tap of the DC reactor. When a load current flowing to the load is smaller than a predetermined value, a circulating current flowing through the positive and negative converters is held at a minimum required value. A circulating current is caused to additively flow for canceling a voltage drop produced across the DC reactor when the load current exceeds the predetermined value.

Active load type of current source and method of making it

Abstract: An active load in an integrated logic circuit of the Direct Coupled FET Logic (DCFL type) in which the active load has a negative threshold voltage and the transistors have a positive threshold voltage. The active load is a transistor, the gate metallization of which is combined with the source metallization. If the active load delivers an excessive current, this current can be adjusted by adding at least one second gate which has a positive threshold voltage and which is in electrical contact with the first gate with a negative threshold voltage. The appropriate threshold voltages are obtained by bombarding the corresponding gate regions. The transistors of the integrated circuit are obtained during the manufacture of the second gate.

Switched direct voltage converter

Abstract: A switched direct voltage converter comprises at least one semiconductor switch (S1) controlled by a control circuit (CC) via a switching input (SI). The semiconductor switch is formed by at least one pair of complementary field effect transistors (T1, T2) connected in a series arrangement (I1) having through-connected voltage-controlled gate electrodes. A converted direct voltage (VS) is obtained by changing over the switch (S1) between first and second supply voltage terminals (VT1, VT2). An input terminal (IT) for connection to a direct voltage supply source (V1) is connected via a coil (L) to a series junction point (SP) between the pair of complementary field effect transistors (T1, T2). A converter output terminal (OT) is connected to one (VT1) of the supply voltage terminals, and a capacitor (C3) is connected between the first and second supply voltage terminals (VT1, VT2) and between the input and output terminals (IT, OT), respectively. As a result, in the pair of complementary field effect transistors (T1, T2') the regular output has become an input (supply voltage connection) and a regular supply voltage terminal has become the output. The field effect transistor property of conducting current in two directions is utilized in the converter. A buffer-integrated circuit may be used with the interchanged connections in the converter.

Performance comparisons of a new negative impedance converter with a translinear implementation

Abstract: A translinear implementation for a negative impedance converter, which is a class A current inversion type (I-NIC) is described. The characteristics of the practical realization are compared with that of the conventional implementation using standard 307 and 741 type operational amplifiers (OA). It is shown that the translinear implementation exhibits increased performances and provides an interesting solution for wideband applications.

Impedance effects on electromagnetic susceptibility

Abstract: This report studies the impedance effects on electromagnetic susceptibility for various loading conditions. From measurements of the self-impedance (Z/sub A/) and received voltage across 50 ohms at the terminals of a generic test object, a Thevenin equivalent circuit model is derived. Then, using this model, the load voltage, current, spectral energy density and accumulated energy are computed for several interesting load impedances. Of interest are two worst cases where the load impedance is the complex conjugate of Z/sub A/ and the conjugate pure reactance of Z/sub A/. Another case of particular interest is where the load impedance is that of an electronic unit representing that of a typical subsystem designed for operation at much lower frequencies. These three cases are compared with the voltage, current and energy at a 50 ohm load. It is concluded that the load voltage, current, spectral energy density and accumulated energy of the two conjugate cases can be one or two orders of magnitude larger than that for the 50 ohm case as might be expected. However, load voltage, current, and spectral energy density at the input of the electronic units tested are comparable to that of the 50 ohm case. The spectral energy densitymore » responses are generally within a factor of two (+-3 dB), but may be as large as a factor of three (+-5 dB) over narrow frequency bands.« less

Charging circuit for battery

Abstract: PURPOSE: To simplify circuit constitution, and to charge a battery effectively by connecting a field effect transistor, to which a voltage drop element having a temperature coefficient is connected, in series with the battery. CONSTITUTION: A voltage drop element 3a having a negative temperature coefficient on a FET 2a operated at positive gate voltage and a voltage drop element 3b having a positive temperature coefficient on a FET 2b operated at negative gate voltage are connected among the FETs 2a, 2b operated at positive or negative gate voltage and gates G and sources S for the FETs 2a, 2b in series with batteries. Constant drain currents determined by voltage Vgs at both ends of the elements 3a, 3b having negative or positive temperature characteristics flow through the batteries 1 and constant current charging is conducted, thus simplifying circuit constitution, then miniaturizing a battery charging circuit. COPYRIGHT: (C)1988,JPO&Japio