Differential amplifier circuit for use in a read channel for a magnetic recording system

A method of operating an integrated circuit comprising the step of:

• applying a differential input signal to a first differential amplifier having inverting and noninverting inputs, and also having inverting and noninverting outputs that produce a differential output signal;
• wherein said first differential amplifier further has a common mode input coupled to receive a feedback signal, wherein the inverting and noninverting outputs of said differential amplifier are coupled through gain control circuits having gains of .gamma. and 1-.gamma., respectively, with the gain of each control circuit being controlled by series resistors coupled between an input signal node and an adder node, with a switch in the form of a MOS transistor connected across a corresponding resistor, and with said adder node coupled to a first input of a second differential amplifier, and with said second differential amplifier having a second input coupled to receive a common mode reference signal and an output that provides said feedback signal.

An integrated circuit comprising:

• a first differential amplifier having inverting and noninverting inputs coupled to receive a differential input signal, and also having inverting and noninverting outputs that produce a differential output signal;
• said first differential amplifier further having a common mode input coupled to receive a feed-forward signal, wherein the inverting and noninverting inputs of said first differential amplifier are coupled through gain control circuits having gains of .gamma. and 1-.gamma., respectively, with the gain of each control circuit being controlled by series resistors coupled between an input signal node and an adder node, with a switch in the form of a MOS transistor connected across a corresponding resistor, and with said adder node coupled to a first input of a second differential amplifier, and with said second differential amplifier having a second input coupled to receive a common mode reference signal and an output that provides said feed-forward signal.

A method of operating an integrated circuit comprising the step of:

• applying a differential input signal to a first differential amplifier having inverting and noninverting inputs, and also having inverting and noninverting outputs that produce a differential output signal.
• Wherein said first differential amplifier further has a common mode input coupled to receive feed-forward signal, wherein the inverting and noninverting inputs of said first differential amplifier are coupled through gain control circuits having gains of .gamma. and 1-.gamma., respectively, with the gain of each control circuit being controlled by series resistors coupled between an input signal node and an adder node, with a switch in the form of a MOS transistor connected across a corresponding resistor, and with said adder node coupled to a first input of a second differential amplifier, and with said second differential amplifier having a second input coupled to receive a common mode reference signal and an output that provides said feed-forward signal.