US Patent 7265926 High speed hard disk drive with symmetric writer

A disk drive data storage system, comprising a magnetic disk a head for writing data to the disk, and circuitry for providing a first voltage (HWX) to a first node (N1) and a second voltage (HWY) to a second node (N2). The first and second voltage circuitry comprises a first transistor (421P2) of a first type and coupled to the first node, a first transistor (422N2) of a second type and coupled to the second node, a second transistor (441P2) of the first type and coupled to the second node, and a second transistor (442N2) of the second type and coupled to the node. The system also comprises circuitry for providing, during a first time period, a first biasing signal (VNDY) and a second biasing signal (VPDY) and circuitry for providing, during a second time period, a third biasing signal (VNDX) and a fourth biasing signal (VPDX).