Showing papers on "Negative impedance converter published in 1969"

Starting and operating control for an ac motor powered by a dc power supply

Abstract: An AC Motor Control, wherein the AC motor is powered by a DC power supply through a DC to AC converter circuit, and wherein the control has an AC current sensor for producing a current signal indicative of the current supplied to the motor which signal is coupled to the converter to prevent excessive current drain on the power supply under starting condition and an AC voltage sensor for producing a voltage signal indicative of the potential across the motor leads and this voltage signal is used to control the converter under operating conditions so that synchronous speed is maintained. Since, under operating condition, the current is inherently substantially stable at rated current, a switch is incorporated responsive to the current signal at rated current to decouple the current signal from the converter and couple the voltage signal thereto.

Phase coherent and amplitude stable frequency shift oscillator apparatus

Abstract: A phase coherent and amplitude stable frequency shift oscillator apparatus comprising a negative impedance converter, biased into an unstable oscillatory condition, in combination with a pair of impedances respectively coupled to the input terminals thereof for determining the frequency of oscillation. One of the impedances includes a series resistive-reactive impedance circuit and the other includes a parallel resistive-reactive impedance circuit. Means are provided for changing the value of the resistive components of the impedances in order to alter the output frequency of the oscillator apparatus and a level limiting and buffering means is provided for stabilizing the oscillatory operation and buffering the output obtained from the apparatus.

Three-port electrical network

Abstract: A three-port electrical network that has a first port whose impedance is high and whose voltage controls the potential of a second port which has low or zero impedance and through which an independent current flows to reappear at a third port at high impedance which consists of a unity gain amplifier having high input impedance and low output impedance and means for deriving a current related to the current flowing in the output port of the amplifier and means for conveying this current to a third port. The latter two means are current followers energized from constant current sources.

Shunt-type negative impedance converter with both short and open circuit stability

Abstract: A shunt type negative impedance converter (NIC) which is normally only short circuit stable is also made open circuit stable by internal circuit action so that it can be used in shunt across telephone trunk circuits to cancel the resistance of central office battery feed resistors. It includes two transistors of opposite conductivity type with a resistive voltage divider and a zener diode controlling the base biasing voltage of the PNP transistor. Whenever a telephone subscriber goes on-hook, presenting a substantially open circuit to the converter, the action of the voltage divider and the zener diode causes both transistors to switch to their nonconducting states.

Integrated circuit periodic ramp generator

Abstract: A temperature stable, low source impedance periodic ramp voltage generator capable of both positive and negative output voltage polarity, or only either one of these, is fabricated in large part as an integrated circuit. The generator comprises the combination of an operational amplifier used as an integrator and a bilateral or unilateral voltage-sensitive switching device, such as a silicon bilateral switch or a silicon unilateral switch, for periodically discharging the feedback capacitor of the integrating circuit.

Matched microwave limiter

Abstract: An improved limiter for microwave circuits to remove voltage applied to a load when the voltage amplitude exceeds a predetermined value without reflections in the circuit. A pair of voltage sensitive switches are connected across a circuit with one switch in series with an insert impedance substantially equal to line impedance. The switches are separated by an impedance inverter to effectively apply a very large impedance across the insert impedance to prevent R-F reflection in the limiting mode.

Impedance measuring device including charging-discharging means

Abstract: A device for measuring the value of an unknown of one of a capacitive impedance and a resistive impedance connected in parallel includes a pulse generator circuit for producing an output in response to a first predetermined voltage across the parallel impedance combination, a circuit for charging the capacitive impedance to a second predetermined voltage greater in value than the first voltage in response to the output of the pulse generator circuit, and a recording circuit for measuring the output o the pulse generator circuit.

Light-coupled, voltage-controlled constant-power source

Abstract: A solid-state circuit for supplying constant power to a varying resistive load in response to a control voltage includes a light source and a photosensitive resistor. Load current is generated by a load current generator operating in response to a control signal. Resultant voltage drop across the load controls a second current generator which is serially connected with a light source. A third current generator, controlled by an independent control voltage, is serially connected with a photosensitive resistor exposed to the light source. Voltage on the photosensitive resistor comprises the control signal which controls the load current generator.

An electrical converter system employing a control converter for controlling the operation of a power converter

Abstract: A converter system utilizing a control converter operated during both the positive and negative current half cycles of the output voltage to initiate firing pulses for a power converter which can be operated in either a noncirculating current mode or a circulating current mode.

Voltage regulating device for generators

Abstract: A voltage regulating device for generators comprising a circuit for detecting the current through a load of a generator; an amplifier circuit for amplifying the output voltage of said load current detecting circuit and a phase control circuit which is driven by the output of said amplifier circuit for controlling the conduction starting phase of the exciting current of the generator in response to the characteristic of the load so as to control the output voltage of said generator and SCR-diode bridge circuit. The output pulses from said phase control circuit lag behind when the load current is high while the output pulses advance when the load current is low, so that the generator may have the characteristic that its output voltage may be dropped at a very steep slope when the load current is increased.