Method and apparatus for adjusting a gain of a variable gain amplifier in a read channel module

A read-channel module comprising:

• a variable-gain amplifier module configured to amplify a signal based on a variable gain;
• an analog-to-digital converter module configured to generate a sample based on the amplified signal;
• an automatic gain control module configured to control the variable gain of the variable-gain amplifier module;
• and
• a gain adjusting module configured to
• in response to an amplitude of the sample being less than or equal to a first predetermined threshold, generate a first gain for the automatic gain control module, wherein the automatic gain control module is configured to increase the variable gain of the variable-gain amplifier module based on the first gain,
• in response to the amplitude of the sample being greater than or equal to a second predetermined threshold, generate a second gain for the automatic gain control module, wherein the automatic gain control module is configured to decrease the variable gain of the variable-gain amplifier module based on the second gain,
• receive feedback of a present gain of the automatic gain control module, and
• generate the first gain and the second gain by (i) multiplying the present gain of the automatic gain control module by a predetermined multiplier or (ii) adding a predetermined offset to the present gain of the automatic gain control module.

A method comprising:

• amplifying a signal and generating an amplified signal using a variable-gain amplifier module having a variable gain;
• generating a sample based on the amplified signal using an analog-to-digital converter module;
• controlling the variable gain of the variable-gain amplifier module using an automatic gain control module;
• in response to an amplitude of the sample being less than or equal to a first predetermined threshold,
• generating a first gain for the automatic gain control module, and
• increasing the variable gain of the variable-gain amplifier module based on the first gain of the automatic gain control module;
• in response to the amplitude of the sample being greater than or equal to a second predetermined threshold,
• generating a second gain for the automatic gain control module, and
• decreasing the variable gain of the variable-gain amplifier module based on the second gain of the automatic gain control module;
• generating a phase information from the sample in response to the amplitude of the sample being (i) greater than or equal to the first predetermined threshold and (ii) less than or equal to the second predetermined threshold;
• and
• suspending determination of the phase information in response to the amplitude of the sample being (i) less than or equal to the first predetermined threshold and (ii) greater than or equal to the second predetermined threshold.

A method comprising:

• amplifying a signal and generating an amplified signal using a variable-gain amplifier module having a variable gain;
• generating a sample based on the amplified signal using an analog-to-digital converter module;
• controlling the variable gain of the variable-gain amplifier module using an automatic gain control module;
• in response to an amplitude of the sample being less than or equal to a first predetermined threshold,
• generating a first gain for the automatic gain control module, and
• increasing the variable gain of the variable-gain amplifier module based on the first gain of the automatic gain control module;
• in response to the amplitude of the sample being greater than or equal to a second predetermined threshold,
• generating a second gain for the automatic gain control module, and
• decreasing the variable gain of the variable-gain amplifier module based on the second gain of the automatic gain control module;
• and
• generating the first gain and the second gain by (i) multiplying a present gain of the automatic gain control module by a predetermined multiplier or (ii) adding a predetermined offset to the present gain of the automatic gain control module.