Showing papers on "Current sensor published in 1976"

A permalloy current sensor

Abstract: The design, fabrication and output characteristics of a thin film Permalloy magnetoresistive magnetic field sensor in a balanced bridge configuration are described. The bridge elements consist of two magnetostatically coupled Permalloy films (100 to 500 A°) separated by a thin film titanium spacer (100 to 1,000 A°). When this bridge is integrated with electrically isolated overlay conductors, the resulting device is ideally suited to sense currents in power supply applications over a 0 to 100 MHz frequency range with negligible dc offset. Devices with 35 mV peak outputs optimized to sense 50, 250 and 500 mA peak currents have been implemented and tested.

Electric vacuum cleaning and agitator motor control system

Abstract: Electrical energization and control circuit particularly for use in permanently installed vacuum cleaning systems having a centrally located A.C. powered vacuum turbine and a remote flexible cleaning unit equipped with low voltage A.C. or D.C. agitator motors. Energization of the A.C. turbine motor circuit is controlled by a current sensor in the one of the two wires leading to the remote low voltage agitator motor so that a selector switch in the handle of the cleaning unit may, in one position, energize the low voltage agitator motor or, in a second position, bypass the agitator motor through a resistance to initiate a current flow that is sensed by the current sensor to activate the A.C. motor circuit.

Integrated FET circuit with input current cancellation

Abstract: An integrated circuit including an FET and an analog for cancelling input current that would otherwise be required to supply the FET gate leakage current. The analog establishes a leakage current the magnitude of which is a substantially fixed proportion of the FET leakage current over a given operating range, and employs proportional current mirror means referenced to the analog leakage current to supply the FET leakage current and thereby substantially cancel the input bias current. In a preferred embodiment the analog comprises a lateral PNP multi-collector transistor with one collector connected to its base to establish a reference current, another collector providing the cancellation current, and its base voltage tracking the FET gate voltage so that the two leakage currents remain substantially equal. An analog FET may also be employed to cancel gate-to-drain and gate-to-source leakages. A description of the invention as applied to an operational amplifier is given.

Current switch circuit having an active load

Abstract: CURRENT SWITCH CIRCUIT HAVING AN ACTIVE LOAD ABSTRACT An improved current switch circuit which has an active load is disclosed. The active load comprises a current source at the collectors of switch transistors which generates a current which is less than the current generated by the current source at the emitters of the switch transistors. The active load also includes a circuit for supplying the current difference between source cur-rents as a supplementary current to the current source at the emitters when the associated switch transistors are conductive and a circuit for diverting the source current at the collectors when the switch transistors are non-conduc-tive. Depending on the current generated by the current sources, the performance of the circuit can be selected to optimize power dissipation versus switching speed. The circuit uses a minimum of resistors and a minimum amount of semiconductor area and thereby ensures low power dis-sipation.

Device for supplying a regulated current

Abstract: A device for supplying a regulated current to an integrated circuit with current injectors. This device comprises two current paths, the currents which flow in the current paths having a fixed ratio which is maintained by means of a current dividing circuit and upon which current a current dependent ratio is imposed by means of a coupling circuit, in order to stabilize two currents. In accordance with the invention at least one of the semiconductor junctions included in the device, which also stabilize the currents, is constituted by the circuit to be powered, which is based on the recognition that the circuit to be powered exhibits a voltage-current characteristic which corresponds to that of a forward-biased semiconductor junction.

Current scaling circuits

Abstract: Each circuit responds to an input current with an output current in fixed ratio to its input current despite variations in the absolute temperature T at which its input and output transistors are operated. Input current from a two-terminal current regulator of a particular type is employed to develop across a resistance a voltage V which varies as a function of T. The input current passing through the resistance serves as the emitter-to-collector current of the input transistor, which is self-biased. The voltage V is applied between the bases of the input and output transistors of the current amplifier for producing the desired output current at the collector of the output transistor.

Current control circuit with current proportional circuit

Abstract: A current control circuit comprises a current proportional circuit having two terminals, the current of one terminal being a proportional relationship with the current of the other terminal. An output terminal coupled with the current proportional circuit and a load through which a controlled current flows, and a constant current source. A steering circuit to which a switching signal is applied, is provided between the two terminals of the current proportional circuit and the constant current source, in order to couple the constant current source to one of the two terminals in response to the switching signal.

Wide range current flow fault detector

Abstract: A wide range current flow fault detector comprising a current sensor and a selective interrogator are disclosed. Current flow, or the lack thereof, between a power supply (e.g., capacitor bank) and a load (e.g, the hammer coils of a line printer) is sensed by a current sensor connected to detect the voltages at spaced points along a selected length of the supply conductor connecting the power supply to the load. A differential amplifier forming a part of the current sensor produces an output voltage related to the voltage difference between the selected points. The output voltage of the differential amplifier is compared, in a comparator, with a preset voltage. Any time the output voltage of the differential amplifier is above the preset voltage, the output of the comparator changes from a first state (e.g., low) to a second state (e.g., high). At all other times, the output of the comparator remains in the first state. Thus, the output state of the comparator denotes the presence or absence of current flow through the supply conductor adequate to cause the output of the differential amplifier to rise above the preset level. The interrogator selectively interrogates the output of the comparator to determine if: (1) a current adequate to raise the differential amplifier output above the preset level exists when such a current should be flowing through the supply conductor; and (2) zero current or a current inadequate to raise the differential amplifier output above the preset level exists when zero or very little current should be flowing through the supply conductor.

Means for controlling the electric current density of a high tension direct current source

Abstract: In a current-density controlled source of high-voltage current fed from a low-voltage current source and supplying a high-voltage direct current to two output terminals, an error voltage resulting from the comparison of a constant reference voltage and the voltage appearing at the terminals of a resistor through which flows a current proportional to the current to be controlled acts on the amplitude of an alternative current signal produced by an oscillator, the amplitude variations of the signal produced by said oscillator causing the amplitude high voltage current supplied to said output terminals to vary.

Device for sensing the operative status of electrical equipment

Abstract: The operative status of an electrical apparatus unit such as a television receiver, incorporating an AC-DC converter, and drawing a substantial amount of current is sensed while differentiating from the usage of a lower amount of current, as when operating in a standby mode. The sensor distinguishes between the standby current waveform and a distinctly different current waveform generated when the AC-DC converter draws current in the mode in which full power is on. The sensor incorporates a reference current detector responsive to the mean of the absolute value of alternating current flowing through a power line to the electrical unit, and a peak value current detector responsive to the peak value of the periodic signal on the power line. A comparator circuit receives outputs from both detectors, and provides an output signal when the ratio therebetween is in excess of a predetermined value, this condition only applying when the AC-DC converter is operative. The comparator may comprise a differential amplifier which periodically triggers a pulse generator to maintain a selected signal level and activate a relay as long as the selected proportionality exists between the peak and mean values of the AC power signal.

High speed current detection amplifier circuit

Abstract: A relatively high sensitivity and high speed current detector consists of essentially a common base differential amplifier consistng of two junction transistors, each having separate emitter and collector resistors, and a constant current source connected to the collector resistors. Separate input terminals connected to the emitters allow complementary information current signals or an information current signal and a reference current signal to be applied to the emitter terminals. The output signal and the complement thereof appear at their respective collectors.