A current determiner comprising a first input conductor and a first current sensor, formed of a plurality of magnetoresistive, anisotropic, ferromagnetic thin-film layers at least two of which are separated from one another by a nonmagnetic layer positioned therebetween, and both supported on a substrate adjacent to and spaced apart from one another so they are electrically isolated with the first current sensor positioned in those magnetic fields arising from any input currents. A first shield/concentrator of a material exhibiting a substantial magnetic permeability is positioned between the substrate and the first input conductor. The substrate can include a monolithic integrated circuit structure containing electronic circuit components of which at least one is electrically connected to the first input conductor. A similar second current sensor can be individually formed, but can also be in the current determiner structure that is supported on the substrate along with a second input conductor supported on the substrate suited for conducting input currents therethrough. This second input conductor is positioned at that side of the second current sensor opposite to that side thereof facing the substrate so as to be adjacent to, yet spaced apart from, the second current sensor to thereby be electrically isolated from any direct circuit interconnection therewith on the substrate but to have the second current sensor positioned in those magnetic fields arising from the input currents in the second input conductor. In addition, a second shield/concentrator layer of material exhibiting a substantial magnetic permeability to serve as a magnetic field concentrator is positioned at that side of the second input conductor opposite to that side thereof facing the substrate. In the first instance, the second shield/concentrator layer is electrically connected to the second input conductor, and can be so connected in the second instance.