Abstract: A circuit for input switching for a read channel is described. The present invention suppresses unwanted signals at the input of a read channel. The present invention uses an open impedance switching circuit to inhibit AC transients during DC bias restoration. One embodiment of the present invention uses a low impedance switching circuit to provide rapid restoration of DC bias levels. Coordination of the operation of the open impedance switching circuit and the low impedance switching circuit is provided to maximize suppression of unwanted signals.

Abstract: A filter boost preattenuator provides controlled, rapid variable signal preattenuation at the input of a filter to optimally compensate for the absolute gain increase of the filter caused by increasing the high frequency boost level of the filter. The amplitude of the filter output exhibits very little change during boost variations that dynamically occur in applications such as data and servo signal recovery in disk drives. Using the present invention, disk space overhead needed to allow for readjustment of the automatic gain control system of a read/write channel is minimized. In the present invention, the feedforward signal provided from the variable gain boost circuit is applied to a feedback circuit and subtracted from the system input. The feedback forces a drop in the overall gain of the filter that increases with boost gain.

Abstract: A method of correcting read channel signal compensation in magnetic storage data storage systems with calibration data stored on select portions of the magnetic recording medium.