A current amplifier includes a cascode transistor for fixing the voltage of an input of the amplifier; a first constant current source connected between the input and a first supply voltage; a second constant current source, for providing a current lower than the first current source, connected between a second supply voltage and the cascode transistor; a second transistor, of different type than the cascode transistor, connected between the input and the second supply voltage, and controlled by...

A current comparator comprises first (1) and second (2) inputs for receiving input currents to be compared. During a first phase (1a) of a clock period the input currents are sensed and stored on first (N1,S7) and second (N2,S8) current memory circuits. On a second phase (1b) of the clock period a switching arrangement (S1 to S4) inverts the input currents and applies them together with the currents stored in the first (N1,S7) and second (N2,S8) current memory circuits to a regenerative latch ci...

A current transformer includes transformer units combined into a bundle, each of the transformer units including an annular iron core surrounding a bus conductor and a secondary winding wound around the iron core for measuring an electric current flowing through the bus conductor, and a shield winding wound around the bundle of the transformer units. The secondary winding may be provided with an air gap in which no secondary winding is present, located at a portion of the current transformer in ...

An integrated circuit amplifier for a high impedance microphone (100) of the capacitance type is disclosed. The subject amplifier circuit permits the further miniaturization of an electret microphone as it is capable of providing an input impedance simulating a resistor value of hundreds of megohms. The circuit particularly comprises duplicate coupling circuits (101a and 101b), a source of reference direct current voltage (103), and a gain providing circuit (102). The coupling circuits (101a and...

A current amplifier uses a current mirror arrangement as an operational amplifier whose output has limited swing. The limited swing is achieved through a plurality of series connected diodes connected to a control input of the amplifier and to the output of the operational amplifier. The control input is coupled through a transistor to inhibit the output of the current mirror arrangement. The output node is coupled to an output for the current amplifier through a Darlington arrangement which pro...

A current measuring system includes three toroidal magnetic cores. The first core has a non-linear B-H characteristic and being adapted for operation in and between its saturation ranges of its B-H characteristic. The second and third cores are adapted for operation in their substantially non-saturating range of their B-H characteristics. The first core is coupled in a flux oscillator configuration to provide a first error signal representative of low frequency flux changes in the core. The firs...

A sensor for measuring large magnitudes of A.C. current utilizes a conductive member having a higher-resistance element parallelled by a pair of elements with lower, and substantially equal, resistance and so arranged as to cause cancellation of magnetic field effects upon the higher-resistance element due to a flow of current through the lower-resistance elements. Thermal-effect compensation of the higher-resistance element of the sensor is also disclosed. Active load termination of a current-s...

A current sensor, integratable with power switching and control circuitry on a common substrate and insulatable from current-carrying conductors, utilizes a piezoelectric element located between a pair of current-carrying conductors. The conductors carry a current flowing in the same direction, causing an attractive force therebetween to act upon the piezoelectric element and generate a voltage therein proportional to the square of the conductor currents. Use of a pair of sensors, each in a diff...

A current amplifier for use with an input voltage comprises a current to voltage converting circuit which converts the input voltage to output currents, and a current multiplier circuit which multiplies the output currents from the voltage to current converting circuit. The voltage to current converting circuit includes first and second transistors each having base, collector and emitter electrodes, with the base electrodes of the first and second transistors being respectively connected to firs...

A current sensor, responsive to the first power of a current to be measured, utilizes a piezoelectric element located between a current-carrying conductor and a permanent magnet having its north-south poles aligned normal to the direction of current flow through the conductor. The substantially constant magnetic field provides a sensor output, taken from electrodes upon opposite surfaces of the piezoelectric member, which is proportional to the first power of current flowing in the single conduc...