Patent ID: 7274523

Claim:
A preamplifier for processing read head signals to correct for thermal asperity transients, comprising: an input gain stage receiving a read head signal from the read head; a correction circuit connected to the input gain stage comprising a filter controller detecting a thermal asperity transient in the read head signal and generating a control signal based on the detecting and further comprising a filter operating dynamically based on the control signal to at least partially filter the detected thermal asperity transient from the read head signal to produce a filtered read head signal; and a reader output buffer receiving and transmitting the filtered read head signal, wherein the filter comprises a voltage controlled high pass filter and wherein the control signal comprises a voltage signal; wherein the filter controller receives as an input signal an output voltage of the voltage controlled high pass filter or an input voltage of the voltage controlled high pass filter; wherein the filter controller comprises a detector for identifying peaks in the input signal and a non-linear function generator, an output of the detector being applied to the non-linear function generator to generate the control signal for the filter; and wherein the non-linear function generator is adapted to produce an increasing function of an absolute value of the output of the detector, the non-linear function generator comprising (|V IN |/V C ) 4 or e |VIN|/VC where V IN is the output of the detector and V C is a control coefficient.