According to one embodiment, an amplification circuit includes a differential amplifier and a feedback circuit. The differential amplifier includes a sampling circuit that samples a first voltage which is a difference between an adjustment voltage supplied to a first terminal and a first input voltage, and a second voltage which is a difference between the adjustment voltage and a second input voltage. The differential amplifier amplifies the first voltage to output a first voltage signal and amplifies the second voltage to output a second voltage signal. The feedback circuit detects a common mode voltage of the first voltage signal and the second voltage signal, and adjusts the adjustment voltage which is supplied to the first terminal in accordance with the common mode voltage.

A method of audio signal processing includes receiving a first audio input signal (first input signal) at an input of a first integrating amplifier of a first single-ended (SE) closed loop channel, and second input signal with a polarity reversed relative to the first input signal at an input of a second integrating amplifier configured of a second SE closed loop channel. During audio signal processing a common-mode (CM) reference voltage level applied to a current source coupled to an input of the first and second integrating amplifiers is dynamically changed including whenever a level of the input signals is below a predetermined low level, reducing the CM reference voltage level for implementing low duty cycle (LDC) PWM operation, and whenever the level is above a level that corresponds to an onset of clipping, increasing the CM reference voltage level for at least reducing the clipping to lower crossover distortion.

Various embodiments of the invention provide for an AC-coupling method and systems that utilize a nested loop circuit to generate a differential mode output that facilitates an offset compensation and a common mode output that facilitates DC-biasing of an active circuit. In embodiments, the nested loop circuit comprises a differential amplifier and a differential mode loop that generates a differential mode output and a common mode loop that uses a common mode voltage and a reference voltage to generate the common mode output.