Marvell Asia Pte., Ltd.

Xiaowei Huang

Yunfan Zhang

Niviya Chacko

Mei Lei

Ma Lin

Su Win Myat

Sheng Ming Lai

Chee Guan Tan

A preamplifier comprises an input stage and a capacitive coupling stage. The input stage is arranged to receive a differential signal from a magnetic resistor which indicates a magnetic field sensed on a magnetic disk of a hard disk drive (HDD) when the preamplifier is powered on from an off state. The capacitive coupling stage has an input arranged to receive the differential signal from the input stage, a filter comprising a first resistor, a second resistor, a first capacitor, a second capacitor, and switches arranged in parallel with respective resistors, where the switches are closed when the preamplifier is powered on from the off state to an on state. A switch control is arranged to determine that an offset of the differential signal has settled and open the switches based on the determination.

Reducing offset of a differential signal output by a capacitive coupling stage of a hard disk drive preamplifier

A bias circuit comprises a closed loop gain stage arranged to determine a difference between a first current in a first branch circuit and a second current in a second branch circuit, where the first branch circuit and second branch circuit are coupled to respective terminals of a magnetic resistor (MR). A first set of current mirrors is arranged to provide a source current to the first terminal of the MR and the second set of current mirrors is arranged to provide a sink current to the second terminal of the MR. The first set of current mirrors and a second set of current mirrors are balanced to reduce a difference in setting time between the source current and sink current. The source current and sink current further reduce the difference between the first current and the second current to provide a constant voltage bias to the MR based on a voltage of a voltage source.

Balanced current mirrors for biasing a magnetic resistor in a hard disk drive

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Singapore, Singapore

Xiaowei Huang