SIGNAL AMPLIFIER AND MAGNETIC SENSOR DEVICE

摘要

<P>PROBLEM TO BE SOLVED: To solve the following problem: in a signal amplifier receiving a very small signal to be detected of a magnetic sensor or the like, a dynamic range can not be secured because the offset of the input signal is large. Ž<P>SOLUTION: The signal amplifier includes an amplifying part 30 for receiving one of differential input signals and an amplifying part 32 for receiving the other, and a common mode detection circuit 28 for detecting a middle point potential of differential output signals obtained from the amplifying parts 30 and 32 and performing feedback control of offset potentials of the differential output signals. The amplifying parts 30 and 32 have bias circuits 36a and 36b for converting middle point differential signals output from differential amplifier circuits 34a and 34b into bias signals to be applied to driver circuits 38a and 38b. Each of the bias circuits 36a and 36b has a resistance variable element whose resistance value changes in accordance with a control signal from the common mode detection circuit 28 to adjust a voltage dividing ratio and adjust the bias signals. Ž<P>COPYRIGHT: (C)2010,JPO&INPIT Ž