Abstract: A data storage system comprises magnetoresistive (MR) sensing elements for sensing data from a recording medium that is referenced to ground, and an amplifier circuit including a biasing stage, an amplifying stage, and a matching stage, each referenced to a common supply voltage source and to ground. The biasing stage includes a reference current source for selectively biasing each MR element with a constant current and, in so doing, developing a single-ended voltage signal having a first dc component. The amplifying stage converts the single-ended voltage signal into an amplified single-ended output voltage signal having a second dc component but in which the first dc component is eliminated. The matching stage creates a bias and imposes said bias on the amplifying stage for converting the single-ended output voltage signal to a differential output voltage signal in which the second dc component is eliminated.

Abstract: Writing of data on a storage disk by an inductive magnetic transducer is modulated by write driver circuitry that includes a supply voltage as low as three volts provided by a source referenced to ground, and a bias current source connected to either the supply voltage source or ground. Two bias control switches respectively direct the bias current to one or the other of two current gain circuits according to whether a positive or a negative input terminal has a preselected polarity. The gain circuits selectively respond to the bias currents supplied by the associated control switch for amplifying the bias current to remove a write current from a respective associated terminal of the transducer.

Abstract: An amplifier circuit is disclosed for simultaneously producing electrical output signals whose magnitude is representative of signals produced by a magnetoresistive (MR) element and protecting said MR element from electrical short circuits between said element and its environment. A means including a first feedback loop biases the MR element with a bias current and amplifies a signal current for causing the MR element to produce a circuit output signal corresponding to dRh/Rh and in which any dc offset error is minimized. Rh is the resistance of the MR element and dRh is the magnetic-signal-induced change in the resistance of the MR element. A second feedback loop insures that the MR element is held at a preselected reference potential and concurrently insures that no current will flow sufficient to damage the element in event of a short circuit between the element and its environment.