Audio input circuit capable of preventing deterioration of total harmonic distortion

An audio input circuit configured to operate in a differential mode, the audio input circuit comprising a differential signal input circuit, a first amplifier circuit, and a second amplifier circuit, wherein:

• the differential signal input circuit includes:
• a differential-circuit first resistor coupled between a differential-audio-signal non-inverting input terminal and a first inverting input of a first amplifier of the first amplifier circuit, wherein the differential-audio-signal non-inverting input terminal is configured to receive a non-inverted component of a differential audio signal;
• and
• a differential-circuit second resistor coupled between a differential-audio-signal inverting input terminal and a first non-inverting input of the first amplifier, wherein the differential-audio-signal inverting input terminal is configured to receive an inverted component of the differential audio signal, and the inverted component and the non-inverted component are complementary signals of the differential audio signal;
• the first amplifier circuit includes:
• the first amplifier including the first inverting input, the first non-inverting input, and a first output, wherein the first output is used to output an inverted audio output signal according to signals received by the first inverting input and the first non-inverting input;
• and
• a first feedback resistor coupled between the first inverting input and the first output;
• and
• the second amplifier circuit includes:
• an input resistor coupled between the first output of the first amplifier and a second inverting input of a second amplifier of the second amplifier circuit;
• a second feedback resistor having one end coupled to the input resistor and the second inverting input, and having another end coupled to a second output of the second amplifier and an output resistor of the second amplifier circuit;
• the second amplifier including the second inverting input, a second non-inverting input, and the second output, wherein the second non-inverting input is configured to receive a common-mode signal, and the second output is used to output a non-inverted audio output signal according to signals received by the second inverting input and the second non-inverting input;
• and
• the output resistor having one end coupled to the second output, and having another end coupled to the differential-circuit second resistor and the first non-inverting input of the first amplifier;
• and
• an output component from the second output of the second amplifier offsets an output component from the differential-circuit second resistor through the output resistor so that the first non-inverting input of the first amplifier receives a DC signal.

An audio input circuit configured to operate in a mixed-signal mode, the audio input circuit comprising a single-ended signal input circuit, a differential signal input circuit, a first amplifier circuit, and a second amplifier circuit, wherein:

• the single-ended signal input circuit includes:
• a single-ended-circuit first resistor coupled between a single-ended-audio-signal input terminal and a first inverting input of a first amplifier of the first amplifier circuit, wherein the single-ended-audio-signal input terminal is configured to receive a single-ended audio signal;
• and
• a single-ended-circuit second resistor coupled between a common-mode-signal input terminal and a first non-inverting input of the first amplifier, wherein the common-mode-signal input terminal is configured to receive a common-mode signal;
• the differential signal input circuit includes:
• a differential-circuit first resistor coupled between a differential-audio-signal non-inverting input terminal and the first inverting input of the first amplifier, wherein the differential-audio-signal non-inverting input terminal is configured to receive a non-inverted component of a differential audio signal;
• and
• a differential-circuit second resistor coupled between a differential-audio-signal inverting input terminal and the first non-inverting input of the first amplifier, wherein the differential-audio-signal inverting input terminal is configured to receive an inverted component of the differential audio signal, and the inverted component and the non-inverted component are complementary signals of the differential audio signal;
• the first amplifier circuit includes:
• the first amplifier including the first inverting input, the first non-inverting input, and a first output, wherein the first output is used to output an inverted audio output signal according to signals received by the first inverting input and the first non-inverting input;
• and
• a first feedback resistor coupled between the first inverting input and the first output;
• and
• the second amplifier circuit includes:
• an input resistor coupled between the first output of the first amplifier and a second inverting input of a second amplifier of the second amplifier circuit;
• a second feedback resistor having one end coupled to the input resistor and the second inverting input, and having another end coupled between a second output of the second amplifier and an output resistor of the second amplifier circuit;
• the second amplifier including the second inverting input, a second non-inverting input, and the second output, wherein the second non-inverting input is configured to receive the common-mode signal, and the second output is used to output a non-inverted audio output signal according to signals received by the second inverting input and the second non-inverting input;
• and
• the output resistor having one end coupled to the second output, and having another end coupled to the single-ended-circuit second resistor, the differential-circuit second resistor, and the first non-inverting input of the first amplifier.