METHOD AND APPARATUS FOR ADAPTIVE GAIN BALANCING OF AT LEAST ONE OF TWO ROTATIONAL SENSORS IN A HARD DISK DRIVE

A hard disk drive and its circuit board and an integrated circuit are disclosed using two piezoelectric devices each having one terminal used to generate signal. The first signal goes to one input of a differential amplifier. The second signal goes to an amplifier whose gain is controlled to create an amplified second signal for the differential amplifier whose output and the first and second signals create a selected signal received by an A/D converter to create a sampled signal used to create a linear disturbance signal and/or a rotational compensation signal, which in turn are used to control the gain of the amplifier to minimize a PES envelope and/or a harmonic PES envelope either in calibration or normal operation of the hard disk drive.