Importance

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Abstract

A circuit for providing a scaled sinusoidal voltage proportional to a sinusoidal current referenced to a first reference potential. The scaled sinusoidal voltage is referenced to a second reference potential. A scaling resistor is connected between an operational amplifier inverting input terminal and the operational amplifier output terminal. A transformer has a primary winding in series with the sinusoidal current. A secondary winding has a first terminal coupled to the second reference potential and a second terminal coupled to the operational amplifier inverting input terminal. An integrator has an inverting input terminal coupled to the operational amplifier output terminal, a noninverting input terminal coupled to the second reference potential and an output terminal coupled to the operational amplifier noninverting input terminal. The operational amplifier provides an output voltage signal to maintain the operational amplifier inverting input terminal at substantially zero volts across the transformer secondary winding. The transformer has a substantially reduced number of secondary turns with a forced zero voltage across the secondary turns increasing the bandwidth over prior art techniques. The integrator responds to the scaled output voltage to provide an average offset bias signal to the operational amplifier noninverting input terminal to enable the operational amplifier to operate in its linear range.

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First Claim