Magnetic-field-sensitive multicollector n-p-n transistors

A recently introduced type of magnetic-field-sensitive silicon microtransducer is described. These devices consist of a multicollector n-p-n transistor fabricated with standard integration techniques. The dependence of output signals on bias conditions, which influence the emitter and collector-current distribution, is analyzed theoretically for both two- and four-collector structures. These one- and two-dimensional vector sensors have been fabricated and tested. The experimental results are compared qualitatively with the theory. Theory and measurements indicate that the two-collector structure gives a differential collector-output current, which is linearly proportional to a magnetic induction, applied along one axis only. Theory and measurements also indicate that the vector sensor gives output signals, which are a linear function of the two components of an in-plane magnetic-induction vector. Consequently, this device is capable of measuring the magnitude and direction of such a vector.