Importance

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Abstract

A write amplifier is provided with one or more improved switching performance, low output common-mode voltage, and precise write head current control. A low output common-mode voltage is achieved using a combination of circuit components which limit the undesirable delivery of current from a differential pair of transistors used for switching, or steering, the current delivered to the write head. Additionally, a voltage source within the amplifier precisely controls the write current delivered to the differential pair. Toward that end, the introduction of operational amplifiers, resistors, and a transistor to provide a circuit wherein the current delivered to the write head by the voltage source is predominantly a function of a write current and a corresponding resistive network, comprised of the write head and resistors connected to the collectors of the differential pair, and wherein the write head current is substantially independent of the current used to perform switching through the differential pair itself. Furthermore, the switching of the differential pair is improved by tying the bases of the differential pair together and capacitively bypassing them to ground and connecting them to an adjustable voltage source, such that the voltage at the bases prevents overdrive of the differential pair of transistor. Additional resistors are also added to damp any remaining transients caused during the switching process.

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