Design and performance evaluation of two novel linearisation circuits for giant magneto-resistance based sensors

This study presents two simple and efficient linearisation circuits for giant magneto-resistance (GMR)-based magnetic field sensors. GMR sensors are commonly available in wheatstone-bridge form, comprising two active GMR and two passive GMR elements. The output of such a sensor possesses a non-linear dependence on the input magnetic field. The proposed linearisation circuits operate on the output of a GMR sensor and provide a linear output with respect to the magnetic field. The first GMR linearisation circuit (GLC1) is based on an enhanced feedback compensation approach, while the second (GLC2) scheme uses a constant current technique. The methodologies of the schemes are described using mathematical derivations. Detailed analyses of the schemes are carried out to bring out the effects of circuit and sensor non-idealities on circuit performance. Further, the circuits were implemented on printed circuit boards and tested. Test results showed the capability of GLC1 and GLC2 to produce linear transfer characteristics. A prototype GMR sensor unit was then fabricated and tested with the developed circuits. Output non-linearity obtained during the experimentation was around 0.7%. Analyses of the results proved the superior performance of GLC1 and GLC2 over the existing schemes.