Calibration of audio power amplifier DC offset

A method of calibrating a DC offset voltage of a system, the system comprising a first operational amplifier (AMP1), a second operational amplifier (AMP2) electrically coupled to the first operational amplifier, a comparator (U3), a digital signal processor (U2), and a digital to analog converter (U1) electrically coupled to the first operational amplifier, wherein the digital signal processor is electrically coupled between the digital to analog converter and the comparator, and wherein at a calibration mode, the method comprises:

• connecting a first input node and a second input node of the first operational amplifier to a common mode voltage (Vcom);
• initially outputting by the digital signal processor a digital code (D[7:0]) having a number of bits at an initial digital value (Vmid) to cause the digital to analog converter to output a first compensation current (Icp) and a second compensation current (Icn) respectively to the first input node and the second input node of the first operational amplifier;
• comparing by the comparator for a number of comparisons a first output voltage and a second output voltage from the first operational amplifier to output each time a digital logical output (0 or 1) to the digital signal processor, wherein the number of comparisons being equal to a number of bits of the digital code;
• responsive to each digital logical output, adjusting the digital code by the digital signal processor by half of the digital code;
• and
• saving the digital code as a compensation voltage value in the digital signal processor after completion of the number of comparisons.