Bipolar magnetotransistor: Relative sensitivity revisited

In this paper we deduce and discuss a new analytical expression for the relative magnetic sensitivity S_r of bipolar magnetotransistors, which incorporates the ambipolar nature of the device operation in the description of the magnetic performance. Our expression accounts for the previously reported [1] trade-off between optimal electrical performance and maximum magnetic sensitivity, commonly found in bipolar magnetotransistors. Moreover, we are able to express S_r in terms of electrical parameters, such as emitter efficiency and common-emitter current gain, physical parameters, like minority carrier diffusion length or minority-carrier lifetime in the base region, and geometrical parameters, like the lateral spacing between emitter and collector.