Using integrated current lines to control the operation point of highly sensitive magnetoresistive sensors

Abstract In highly sensitive magnetic sensors coupled to magnetic flux concentrators, the optimal operation point with maximum sensitivity may appear deviated from zero magnetic field. Such characteristic can hamper the detection of very low magnetic fields. In this work a magnetic bias technique is presented which allows an efficient control of the operation point of the magnetoresistive sensor placed in the gap of two magnetic flux concentrators. Specifically, the magnetic field created compensates the shift of the output curve and is here generated by a current line directly integrated on chip. This method allows to control the input current and, therefore, change the local magnetic field towards a fine tuning of the offset field. The optimum configuration includes 44 current lines with 2.3 mA on top of each magnetic flux concentrator yielding a shift of 0.1 mT.