Kopfleseverstärkerschaltung

In accordance with the present invention, a magneto-resistive head read amplifier circuit is provided which can be incorporated into a magnetic reader for reading information stored in magnetic form on a storage medium. The magneto-resistive head read amplifier of the present invention incorporates an inductor in the bottom current drain of the head read amplifier circuit which reduces or eliminates noise generated by the bottom current source transistor of the head read amplifier circuit. In accordance with a first embodiment of the present invention, the magneto-resistive head read amplifier is a single-polarity head read amplifier circuit which utilizes a bias current having a particular polarity. In accordance with a second embodiment of the present invention, the magneto-resistive head read amplifier is a dual-polarity head read amplifier circuit capable of operating with bias currents of opposite polarity. Both embodiments of the present invention preferably utilize a common mode feedback circuit and a differential feedback circuit which set the operating point of the head read amplifier circuits. The differential feedback circuit nulls the differential output voltage of the head read amplifier circuit and the common mode feedback circuit sets the minimum bias current for the magneto resistor. In the dual-polarity head read amplifier circuit, switching logic is utilized to enable the polarity of the bias current to selected.