Temperature-compensating amplification circuit and a position detecting apparatus using such amplification circuit

摘要

Magnetic resistive elements 4 and 5 cooperatively detect the change of the magnetic field responsive to the rotation of a gear 2 fixed to a shaft 1. An amplification circuit 6 comprises an operational amplifier 7 having an input terminal to which a gain-determining input resistor 8 is connected. A gain-determining feedback resistor 9 is provided in a feedback path of the operational amplifier 7. The gain-determining resistors 8 and 9 are formed by a P well region and a P+ region of a MOS process element. The temperature characteristics of the gain-determining resistor 8 and 9 are opposed to that of the magnetic resistive elements 4 and 5. The temperature characteristics of the gain of the operational amplifier 7 cancel the temperature characteristics of the magnetic resistive elements 4 and 5.