Audio circuit

An audio circuit comprising:

• a class D amplifier circuit structured to receive an analog audio signal with a first reference voltage as a center level, and to output an output pulse signal having a duty cycle that corresponds to the analog audio signal;
• and
• a bias circuit structured to generate a second reference voltage having a voltage level obtained by dividing the first reference voltage and a power supply voltage,
• wherein the class D amplifier circuit comprises:
• an integrator structured to receive the analog audio signal and a feedback signal that corresponds to the output pulse signal;
• a periodic voltage generating circuit structured to generate a periodic voltage having a triangle waveform or a sawtooth waveform;
• a Pulse Width Modulation (PWM) comparator structured to compare an output of the integrator with the periodic voltage;
• a bridge circuit structured to receive a supply of the power supply voltage;
• and
• a driver structured to drive the bridge circuit according to an output of the PWM comparator,
• wherein the integrator comprises:
• a first operational amplifier structured to receive the second reference voltage via a non-inverting input terminal;
• a first resistor structured such that the analog audio signal is input to one end thereof, and the other end thereof is coupled to an inverting input terminal of the first operational amplifier;
• and
• a second resistor structured such that the feedback signal is input to one end thereof, and the other end thereof is coupled to the inverting input terminal of the first operational amplifier,
• and wherein the periodic voltage generating circuit generates a periodic voltage having an amplitude that corresponds to the second reference voltage.