A current sensor for use with a conductor with known cross-sectional characteristics is an electronic circuit having a monolithic Hall-effect element disposed substantially perpendicular to the conductor first major surface. A conductive loop substantially encircles the element and is oriented such that its flux is substantially orthogonal to the element surface. An amplifier sets current flow in the loop responsive to minimization of the differential Hall voltage across element. The loop current, at null, will be related to the conductor current by the ratio of the conductor flux path length to the loop flux path length.