Hall effect elements are known. A typical planar or horizontal Hall effect element is a four terminal device for which a drive current (a DC current) is passed between two opposing ones of the four terminals and a differential voltage (AC or DC), responsive to a magnetic field (AC or DC), is generated between the other two opposing ones of the four terminals. An amplitude of the differential signal (i.e., voltage) is related an amplitude of the drive current. Thus, a sensitivity (e.g., mV per Gauss) of the differential signal is related to the amplitude of the drive current.
The Hall effect element can be used in current spinning or chopping arrangements in order to reduce a DC offset from the Hall effect element, which is typified by a non-zero output voltage from the Hall effect element even when experiencing a zero magnetic field. With current spinning or chopping, the terminals used to pass the drive current and the terminals used to generate the differential signal can be changed at a current spinning rate in a periodic and cyclic manner. There can be two such changes per cycle with two-phase current spinning or four such changes with four-phase current spinning.
In order to maintain a constant and stable sensitivity, the drive current can be generated with a stable current source or a current sink that uses a stable reference voltage. However, various parameters can cause the sensitivity to magnetic fields of the differential signal to change.
In general, even with a perfectly stable drive current, the Hall effect element itself can experience sensitivity changes. The changes in sensitivity of the Hall effect element can result directly from temperature changes. In order to correct for this sensitivity change, temperature can be sensed and the changes in sensitivity with temperature can be corrected.
However, the changes in sensitivity of the differential signal can also result from stresses upon a substrate on which the Hall effect element is disposed. The stresses may or may not be related to temperature and also may or may not be related to a thermal coefficient of a material of a package used to seal the substrate. The stresses and resulting changes in sensitivity may vary from unit to unit in different ways with respect to temperature.
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