At its most basic, a Hall effect sensor is a magnetic field sensor which provides an output voltage related to a sensed magnetic field. Linear Hall effect sensors, for example, provide a linear relationship between an output voltage and a characteristic of an applied magnetic field and can include ordinary Hall plates as well as vertical Hall effect devices.
In many Hall effect sensor applications, e.g., differential sensing, desired sensor characteristics include low residual offset error (e.g., a non-zero output signal when there is zero applied magnetic field), low signal-to-noise (S/N) ratio and high bandwidth. To reduce or eliminate residual offset error, Hall effect sensors often are operated using spinning current schemes or techniques in which use of sensor contacts as output signal contacts, voltage or current supply contacts, and/or ground contacts is switched during different operating phases of the sensor, and the output signals from each operating phase are later combined.
Residual offset errors can relate to the voltage applied to the Hall effect sensor; for example, a higher voltage applied to a Hall plate can result in a higher residual offset error because of nonlinear effects (e.g., junction field effects from substrate potential to the Hall plate or thermo-dynamic effects). Thus, lower applied voltages can be preferred. At the same time, however, a high bias voltage can be necessary to improve the S/N ratio because the S/N ratio increases proportional to the bias voltage. Balancing these two characteristics often leads to compromise in the design of Hall effect sensor devices and circuits, such that neither the residual offset error or the S/N ratio is particularly poor. Of course, this results in neither being particularly good either. For example, one conventional approach in Hall effect sensor devices uses a fixed bias voltage optimized for noise. Still other approaches modulate the bias voltage or use stacked or similar Hall plate configurations. While these approaches can offer improvements, they still operate as compromises, leaving room for improvement in the design and operation of Hall effect sensor circuits and devices.
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