Average Value Extractor Is More Precise Than Low Pass Filters

Focus:

When designing ac current sensors, we use the current’s average value to create a voltage that mitigates the error caused by dc offset in the system of integrator and amplifiers. While it’s possible to obtain the average value of an analyzed signal through use of a low-pass filter, the filter narrows its operating frequency range. However, with an op amp, we can subtract an ac component from a signal composed of this ac component and the dc offset This article derives the equations for an average value extractor circuit built from an op amp-based, differential amplifier. Then it demonstrates how this average value extractor can be used to perform dc stabilization of a Rogowski integrator circuit.

What you’ll learn:

• How to dc stabilize a Rogowski integrator circuit using an average value extractor circuit
• How to remove a dc offset while measuring making wide-bandwidth ac current measurements

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Author & Publication:

Gregory Mirsky, Design Engineer, Deer Park, Ill., How2Power Today, Dec 15 2025

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