Amplification circuit

An amplification circuit for an MR head which can realize a reduction of the power consumption, simplification of the circuit configuration by providing capacitors inside the circuit, and reduction of the number of externally provided parts, wherein a current is supplied to an MR head resistor from a bias current source and the amount of change of the head resistance is converted to a voltage change when reproducing magnetically recorded data. A direct current component of the voltage dropped in the head resistor is cut by capacitors, and only the alternating current component is input to a differential amplification circuit configured by transistors. Recorded data can be distinguished in accordance with an amplified output voltage, so capacitances of direct current cut-off capacitors can be set small and thus the direct current cut-off capacitors can be provided in the IC chip and the number of external parts can be reduced. Furthermore, since the base bias voltages of the transistors are set independently from the MR head, the power consumption can be reduced.