4.2 MagFET

The magnetic field sensitive MOSFET (MAGFET) is used as a sensor to convert the magnetic field applied perpendicular to the channel to an electrical signal, like current, voltage, or frequency [143]. Integrated magnetic field sensor arrays can detect variations of the magnetic field in a small area. Such sensor arrays are used, e.g., to determine fringing fields in electrical motors or to detect defaults in metallic pipes [144]. Magnetic sensor arrays have been fabricated up to sizes of about $ 1\,{\mathrm{cm}}^2$ and are also used to detect non-magnetic quantities like currents by their surrounding magnetic field, displacement of magnets, or the movement of membranes to which magnetic dipoles have been applied [145]. Thus, two different applications can be distinguished:

Direct applications
are used to measure the magnetic field and are the main goal for investigations on MagFETs. Some examples are the measurement of the geomagnetic field, detection of the magnetic field on magnetic cards or banknotes, or to read data of magnetic data storage medias.
Indirect applications
use the magnetic field to determine different physical quantities like potential-free current detection mentioned above, contactless switching, or the measurement of angles or velocities where an auxiliary permanent magnet is used.
These applications require the detection of magnetic fields in the range between $ 1\,\mu{\mathrm{T}}$ and $ 1\,{\mathrm{T}}$ [146].

Robert Klima 2003-02-06