Showing papers on "Negative impedance converter published in 1973"

Impedance measuring system

Abstract: There is disclosed a constant magnitude alternating current source connected to at least one electrical impedance to be measured. First and second voltage detectors are connected to the electrical impedance to measure voltage across first and second portions of the electrical impedance, respectively, in response to the current conducted from the current source. A computer is attached to the first and second voltage detectors for processing the measured voltage to compute desired characteristics of the electrical impedance.

Impedance simulating circuit for transmission lines

Abstract: A circuit for simulating the presence of positive or negative impedances in shunt or in series with a transmission line. A voltage generating circuit generates an impedance simulating voltage and introduces that voltage in series with the transmission line. A current generating circuit generates an impedance simulating current and introduces that current in shunt with the transmission line. Current feedback circuitry controls the voltage generating circuitry in accordance with the amplitude of the signal current in the transmission line to simulate either a positive or negative series impedance. Voltage feedback circuitry controls the current generating circuitry in accordance with the signal voltage across the transmission line to simulate either a positive or negative shunt impedance. Circuitry is also provided to afford these simulated impedances in the presence of echo suppressing and impedance matching characteristics.

Two-phase solid state power converter

Abstract: A driven two-phase power converter such as a DC-to-AC inverter or boost converter is modified by the incorporation of a unique differential current transductor and transistor pulse drive circuit. The differential current transductor senses any difference in the average current in the two legs of the twophase power converter circuit and produces a voltage proportional to that current difference. This voltage is then used in the pulse drive circuit to control, on a half-cycle basis, the widths of the drive pulse to the switching transistors in a manner which equalizes the currents in the two legs.

Method and apparatus for measuring the impedance of a line

Abstract: A method and apparatus for measuring the impedance of a line in which the resistive and inductive component of line impedance are determined from measured instantaneous values of voltage, current and the rate of current change using a digital computing circuit.

Voltage regulator with controlled current

Abstract: A voltage regulating system for AC generators including a three phase current boost and a voltage responsive control circuit having a full converter type output stage. The three phase boost circuit and the full converter output stage are connected in series with the field winding of the exciter. At high power output levels, the inverting capability of the full converter power stage is used to oppose the voltage generated by the current boost to prevent loss of control over the generator, by diverting excessive boost currents through a load means connected to the current boost circuit.

Flame detection system with compensation for the flame detector

Abstract: A flame detection system utilizes a flame responsive impedance, such as a lead sulphide photocell, and responds to the change in infrared radiation and the flame flicker frequency of the sensed flame. The flame responsive impedance is connected through a variable impedance means to a source of direct current voltage. The voltage between the flame responsive impedance and the variable impedance means is compared by an amplifier to a voltage divider network so that a feedback voltage can be generated by the amplifier to control the variable impedance means. The variable impedance means is controlled by the feedback so as to keep the direct current voltage across the flame responsive impedance constant to compensate for variations in flame background radiation, and cell to cell variation. The system then uses a band-pass amplifier and detector-integrator system to control an output switch.

Measuring apparatus utilizing variable impedance elements

Abstract: The measuring apparatus comprises an impedance element which is energized by a reference voltage of a predetermined voltage level and has its impedance varied with variations in the physical properties of an object to be measured, and a negative impedance network, with its input impedance set at a negative value, which includes an amplifier and a positive feedback impedance element connected between the input and output terminals of the amplifier and is connected in series or parallel with the first mentioned impedance element. With the arrangement, the variations in the physical properties of the object can be detected in an extremely enlarged state in the form of a terminal voltage appearing across the first mentioned impedance element or an output voltage appearing across the output terminals of the negative impedance network.

Compensated transformer circuit utilizing negative capacitance simulating circuit

Abstract: A circuit for reducing or eliminating the effect of the stray capacitance of the windings of a transformer on signals coupled through that transformer. Circuitry is provided for generating voltages and currents which simulate the presence of a negative capacitance and for coupling those voltages and currents to a transformer in cancelling relationships to the stray capacitance thereof. Circuitry is also provided for imposing an upper frequency limit beyond which capacitance cancellation will not occur. The upper frequency limit stabilizes the circuitry and allows signal transmission to be limited to a predetermined desired band of frequencies.

Voltage-to-current converter and function generator

Abstract: A voltage-to-current converter serving as a function generator or an essential element thereof and producing various output voltages in accordance with an input signal. It comprises a voltage-to-current converter circuit including at least two transistors, one of these transistors being an output transistor carrying current proportional to the potential difference between two input terminals respectively connected to the emitters of the two transistors, and a current-to-current converter providing at an output terminal a current proportional to the current through the afore-mentioned output transistor. With this voltage-tocurrent converter a function generator of a simple circuit construction may be produced inexpensively. Also, it may be readily made as a semiconductor integrated circuit.

Apparatus for regulating a d.c. voltage

Abstract: Apparatus for regulating a d.c. voltage appearing across a load. The emitter-collector junction of a transistor is connected in series with a retardation coil and with the load impedance to a d.c. voltage source. The voltage applied to the load impedance is compared with a reference voltage in a regulating circuit. The latter circuit provides an output signal of a value which is a function of the d.c. voltage appearing across the load impedance. The conductivity of the emitter-collector path of the aforementioned transistor is controlled by the latter output signal. An adjustable impedance is connected in series with the primary winding of a transformer and to the voltage source. The secondary winding of the transformer is connected across the base-emitter junction of the aforementioned transistor, and the signal appearing across this winding controls the operation of the transistor. A frequency generator produces a timing signal, which through the regulating circuit, produces an edge of the output signal. The other edge of the output signal is a function of the d.c. voltage appearing across the load impedance.

Negative impedance converter

Abstract: A semiconductor negative impedance converter device for compensation of insertion losses attributable to the use of high impedance devices such as semiconductor controlled rectifiers in solid state telephone switching networks. The device comprises a double collector PNP transistor and an NPN transistor which can be fabricated in a single semiconductor substrate without the need for isolation of their various regions.

Active shunt impedance for compensating impedance of transmission line

Abstract: An active shunt impedance compensating circuit for a two wire transmission line. A pair of output terminals connect across the transmission line. A negative impedance converter has a negative impedance circuit connecting side and a positive impedance connecting side. The positive impedance circuit connecting side is coupled across the pair of output terminals. First series connected resistance and capacitance impedance elements are connected across the negative impedance circuit connecting side. Second series connected resistance capacitance and inductance impedance elements are connected across the positive impedance circuit connecting side. A negative impedance converter is characterized, assuming an ideal transformation, for forming an equivalent circuit substantially equal to the negative of the first series connected impedance elements in parallel with the second series connected impedance elements.

A surface-controlled negative impedance transistor

Abstract: A negative impedance transistor is described in which a gate on the oxide over the emitter-base junction and attached to the collector causes the collector current I C to decrease when V CE exceeds a critical value. For high V CE , I C eventually increases as breakdown is reached. When operated with a fixed external base current drive, the I C - V CE characteristic is similar in shape to the I-V characteristic of a tunnel diode. The ratio of the peak-to-valley current, and the voltage range over which the negative impedance effect occurs, are shown to be strongly dependent on the base surface concentration, oxide thickness, and the external base current drive. Two models are presented which predict the variation in the base current with gate voltage in terms of base surface recombination and surface potential. These models may be extended to describe the variation in I C with V CE for a constant external base current drive. Two sample applications of the gated transistor are presented.

System for controlling the frequency of an alternating current converter in response to load changes

Abstract: Alternating current having a selected frequency is produced by a converter to operate a synchronous motor at a desired speed. The frequency of the alternating current is determined by an accumulating circuit that supplies synchronizing impulses to the converter at a rate determined by the setting of the accumulating circuit and in response to a pilot signal. During failure of power to run the converter, a trigger generator responsive to voltage from the decelerating motor changes the control setting of the circuit so that, upon restoration of power, synchronizing pulses will be produced at a lower repetition rate, causing the frequency of alternating current from the converter to be commensurate with the reduced speed of the motor.

A high input impedance buffer amplifier using bipolar transistors

Abstract: The input impedance of conventional emitter follower circuits is limited due to the finite value of the passive emitter resistance, shunting effect of biasing resistors and that of intrinsic collector to base feedback admittance and also to the fall in current amplification factor at low operating currents. Further, the input admittance is frequency dependent because the device parameters involved therein are themselves frequency dependent. However, the shunt positive feedback incorporated in such circuits minimizes the shunting effect of the biasing network and also that of the intrinsic feedback admittance. The simulation of negative capacitance across the input terminals nullifies the effect of the presence of the otherwise positive capacity. This technique extends the bandwidth over which the input impedance remains constant. A typical buffer amplifier circuit employing five conventional epitaxial planar bipolar silicon transistors has been described in the present communication. The input im...

Open-circuit voltage transfer-function synthesis using the generalized positive impedance converter

Abstract: An open-circuit voltage transfer-function synthesis procedure is presented that realizes any arbitrary real rational function in the complex variable s. The procedure makes use of an active device referred to as the generalized positive impedance converter (GPIC). The synthesis procedure yields a network realization that 1) requires the minimum number of capacitors necessary for the synthesis, 2) is compatible with integrated-circuit fabrication techniques, and 3) has low sensitivity.

Gain control circuit having variable impedance to determine circuit gain and to control minimum gain

Abstract: A gain control circuit in which a variable impedance to control the gain is placed in parallel with a relatively constant current circuit, and the constant current is proportional to the signal voltage to be controlled. These parallel-connected components are connected in series with an impedance in the emitter circuit of a common base amplifier. A load impedance is connected in the collector circuit of the amplifier and the output signal is derived across the load.

Some negative impedance converters

Abstract: Four new transistor-resistor negative impedance converter circuits are presented, two of the voltage-inversion type and two of the current-inversion type. Their gain-product sensitivities are tabulated.

Impedance Characteristics of TRAPATT Oscillator Circuits

Abstract: An accurate, closed-form analysis has been developed for calculating the harmonic matching impedance required for a time-delay-triggered TRAPATT oscillator. Quantitative agreement was obtained with experimental impedance measurements on an S-Band oscillator.