Abstract: A low cost disk drive system includes track zero information located in a single sector on the disk surface. The information is comprised of a first type of signal located in tracks to one side of an arbitrary reference track and a second type of signal located in the tracks to the other side of the arbitrary reference track. The magnetic head of the disk drive system is moved radially with respect to the disk and the transition between the signals detected in order to locate the head at the reference track.

Abstract: The track access time in a disk drive system is minimized by determining an optimum velocity profile each time the system is operated. The optimum velocity profile is determined by performing repeated seek operations with successively higher velocity profiles until a seek failure occurs. A velocity profile slightly lower than the profile which caused failure is then used to control seek operations. During seek operations, the time between track crossings is monitored and the velocity profile reduced if the transducer of the disk drive system is not adequately following the preset velocity profile.

Abstract: An amplifier for bidirectionally driving a motor includes circuitry for enabling the amplifier to operate with a bipolar input signal while employing a single power supply. The amplifier includes an input section which receives the bipolar input signal and provides a unipolar output voltage. The operational amplifier drives a bridge drive network to provide a drive current to output bridge transistor in one of two directions. The bridge network includes control circuitry for causing all of the transistors of the drive bridge to be operated in their active regions, thereby improving the power dissipation characteristics of the network. The output bridge transistors are also controlled to operate in their active regions. In addition, circuitry is included for providing negative feedback for the amplifier despite the fact that the output current is always a positive current.