A novel 0.7 V high sensitivity complementary differential MAGFET sensor for contactless mechatronic applications

This paper discusses the design of a novel low-voltage complementary differential magnetic field effect transistor (CDMAGFET) with enhanced magnetic field sensing capability compared to previously reported NMOS only MAGFET or the single-ended cross-coupled MAGFET (CCMAGFET). It uses split-drain concave NMOS and PMOS devices which are cross-connected and operated differentially to provide an enhanced sense voltage. Simulations using the IBM 130 nm CMOS process technology indicate that it has almost double the sensed voltaic output (VSENSE) for the same magnetic field intensity (BZ) applied in quadrature to the MAGFET plane. Short channel devices are used for this design and comparison. The NMOS MAGFET had a sensing channel area of 2 × 0.13 μm × 30 μm while the PMOS MAGFET had a sensing channel area of 2 × 0.13 μm × 150 μm. Depending on the operating bandwidth the sensing channel area can be linearly increased in order to increase the mTESLA vs. channel area sensitivity of the MAGFET (usually by using longer channel length). Careful CDMAGFET layout techniques are discussed to eliminate DC offsets in the presence of a DC magnetic field. Also, in order to minimize the transversal thermal noise current in an AC magnetic field a very low CDMAGFET bias current is used. Experimental verification of the nanometric CDMAGFET operation in the presence of orthogonal DC and AC magnetic field is also reported. The measured relative DC and AC voltaic sensitivity for the experimental CDMAGFET was, respectively, 0.564 and 1.65 mV/(V mTESLA) (the peak AC sensitivity @ 250 kHz).