Method and apparatus for reducing asymmetry in a signal from a magneto-resistive read head

A circuit for processing an analog output signal from a read head having a nonlinear transfer function, said circuit comprising:

• a nonlinearity correction circuit which has an input coupled to receive the analog output signal and which is operative to generate a corrected analog signal by adjusting the analog output signal to reduce a nonlinearity introduced by the read head;
• said nonlinearity correction circuit including an asymmetry compensation circuit which has an input coupled to receive the analog output signal and which is operative to generate an analog compensation signal representative of the nonlinearity introduced by the read head, and including circuitry operative to combine the analog compensation signal with the analog output signal to obtain the corrected analog signal;
• wherein said asymmetry compensation circuit generates the analog compensation signal as the square of the analog output signal multiplied by an asymmetry factor;
• and including a low pass filter having an input to which the corrected analog signal is applied, said low pass filter having an output which is coupled to an output of said circuit.

A circuit for processing an analog output signal from a read head having a nonlinear transfer function, said circuit comprising:

• a nonlinearity correction circuit which has an input coupled to receive the analog output signal and which is operative to generate a corrected analog signal by adjusting the analog output signal to reduce a nonlinearity introduced by the read head;
• said nonlinearity correction circuit including an asymmetry compensation circuit which has an input coupled to receive the analog output signal and which is operative to generate an analog compensation signal representative of the nonlinearity introduced by the read head, and including circuitry operative to combine the analog compensation signal with the analog output signal to obtain the corrected analog signal;
• wherein said asymmetry compensation circuit generates the analog compensation signal as the square of the analog output signal multiplied by an asymmetry factor;
• and including an asymmetry setting circuit which supplies to said asymmetry compensation circuit a signal defining the asymmetry factor.

A circuit for processing an analog output signal from a read head having a nonlinear transfer function, said circuit comprising:

• a nonlinearity correction circuit which has an input coupled to receive the analog output signal and which is operative to generate a corrected analog signal by adjusting the analog output signal to reduce a nonlinearity introduced by the read head;
• said nonlinearity correction circuit including an asymmetry compensation circuit which has an input coupled to receive the analog output signal and which is operative to generate an analog compensation signal representative of the nonlinearity introduced by the read head, and including circuitry operative to combine the analog compensation signal with the analog output signal to obtain the corrected analog signal;
• wherein said asymmetry compensation circuit generates the analog compensation signal as the square of the analog output signal multiplied by an asymmetry factor;
• including an asymmetry setting circuit which supplies to said asymmetry compensation circuit an asymmetry factor signal defining the asymmetry factor;
• and wherein said asymmetry compensation circuit includes a first predistortion circuit operative to preadjust the asymmetry factor signal to compensate for a first distortion characteristic, a first multiplier which has the first distortion characteristic and which is operative to multiply the predistorted asymmetry factor signal from said first predistortion circuit by the analog output signal, a second predistortion circuit which is operative to preadjust the output of said first multiplier to compensate for a second distortion characteristic, and a second multiplier which has the second distortion characteristic and which is operative to multiply the output of said second distortion circuit by the analog output signal.