5.1 The Structure

A three-drain MAGFET is as old as the first MOS Hall plate device [14]. It was first proposed in [10,20] where it is suggested to bound together the Hall voltage terminals and the drain to form a three-drain MAGFET. As stated by Gallagher [14], in a MOS Hall plate device the Hall voltage terminals should be placed as close as possible to the drain terminal in order to sense the Hall voltage and not to interfere with the electric behavior of the MOSFET. That is the reason why in [10,20] the proposal of a three-drain MAGFET using Hall plates has been given. By taking the central drain current as a reference, a differential current is sensed on the lateral drains. However, no simulation results or experimental data showing the three-drain MAGFET as a magnetic sensor with a differential current output have been published yet.

In principle, the three-drain MAGFET looks exactly as a two-drain MAGFET (see Figure 4.1). The only difference is that the drain is split in three parts. Because of the lack of experimental data, this chapter only shows simulation results of this structure using the characteristics of a 10 $\mu$m standard CMOS process. In the following analysis the investigated three-drain MAGFET has a $W/L$ ratio of $0.64$ ( $W = 80\,\mu$m and $L = 125\,\mu$m) and a distance between the drains of $10\,\mu$m.

Figure 5.1: Three-drain MAGFET structure.