Magnetic-field vector sensor based on a two-collector transistor structure

Abstract

The paper describes a silicon micro-transducer which is capable of measuring two components of a magnetic-field vector at the same time. The good linearity along both main sensing axes is demonstrated both theoretically and experimentally. This offers the possibility of using the device for rotation or angle measuring as well as for merely field monitoring purposes. In a wide range of field strengths the angle information of the sensor's output is independent of the magnitude information. Thus a degradation of permanent magnetic properties in time would not demand a recalibration of the sensor, if used as a contactless angle detector. The device consists of a planar four-collector npn-transistor, which is fabricated in a standard bipolar integration process. The Lorentz force acting on electrons in the collector region is exploited in such a manner that small current differences between collector contacts occur. These currents appear to be proportional to the induction vector components.