Voltage amplifier for constant voltage biasing and amplifying signals from a MR sensor

摘要

An amplifier for voltage biasing and amplifying the signals produced by a magnetic sensor is provided. Electrically, the resistance of the sensor is disposed between the bases of a differential pair comprising the input stage of the amplifier. Constant bias voltage for the sensor is provided independently of sensor resistance. DC feedback to the input stage balances current flow in both paths of the differential input stage to correct for DC offset arising in the output from input stage emitter resistor. The amplified signal, representing DELTA Rh/Rh, is sensed as a voltage across the magnetoresistive sensor, where DELTA Rh is the change in steady-state resistance, Rh, of the sensor.