Improvements in or relating to hard disk drives

摘要

An improved write drive circuit which includes a discharge circuit 22 added to the base of the bottom transistors 24 of the H-bridge to prevent excessive overshoot and ringing while allowing for higher data rates. The discharge circuit 22 is turned on after the head voltage or current reaches an overshoot condition. In preferred embodiments, the discharge circuit includes variable discharge capability by selecting one or more parallel drive transistors or varying a variable delay in the discharge circuit or any combination of both variables. Both can be controlled by a word written to the disk drive pre-amp over the serial control port.