Research Of The Relative Sensitivity Of The Sector Split-Drain Magnetic Field-Effect Transistor

In this paper the relative sensitivity of the sector split-drain magnetic field-effect transistor (MAGFET) has been studied.With the rapid development of society and technology, the traditional sensing technology cannot satisfy the demand of more and more complicated application conditions and environments. It is the trend of modern sensor technology to design and fabricate intelligent integrated microsensors which are suitable for multiple dimensions and multiple parameters sensing.MAGFET can be connected to electric circuits directly to transduce the magnetic signal into electric signal. The fabrication of MAGFET is completely compatible with the semiconductor integrated circuit process. Therefore it is convenient to design monolithic sensor system including sensing devices and signal processing circuits.The sector split-drain magnetic field-effect transistor is a kind of novel MAGFET whose maximum experimental relative sensitivity is 3.77%/T. Its sensitivity is higher than the traditional rectangular MAGFET, so the study of the relative sensitivity is of great value.The relative sensitivity of the sector split-drain field-effect transistor is studied by two methods:1. Numerical simulation. The distribution of voltage and current inside the device are obtained by solving a set of semiconductor equations. Based on the current density, the numerical model of relative sensitivity is established. In the simulation a channel charge equation is modified to include the magnetic modulation effect in carrier mobility equation. The mobility model containing magnetic signal improves the accuracy of computation.2. Analytic model. Using conformal mapping technique the physical relation between sector and rectangular device is established. Based on the relation, geometrical factor of sector split-drain MAGFET is obtained. The analytic model associated with split-drain current difference is proposed by integrating the two-dimensional current equation in the definition domain of device channel.The testing chips are designed with Shanghua 0.6μm CMOS mixed-signal technology. Analytic and numerical models of sector MAGFET are verified by the experiments and are used to optimize the sensing devices which are applicated to design magnetic sensor integrated circuits. The preconditioning circuits of magneticsensor combine sector MAGFET, synchronous sampling function mode and correlated double sampling technique. Compared with asynchronous sampling mode, synchronous circuit has the advantages of short sampling period and small distortion.