Audio input circuit which avoids deterioration of total harmonic distortion

Abstract

An audio input circuit capable of avoiding the deterioration of total harmonic distortion (THD) includes a single-ended signal input circuit, a differential signal input circuit, a first amplifier circuit and a second amplifier circuit. The single-ended signal input circuit is enabled by a switch in a single-ended mode to output a single-ended audio signal to the first amplifier circuit. The differential signal input circuit is enabled by a switch in a differential mode to output a differential audio signal to the first amplifier circuit. The first amplifier circuit outputs an inverted audio output signal to the second amplifier circuit according to the signal received thereby. The second amplifier circuit outputs a non-inverted audio output signal according to the signal received thereby. In the single-ended and differential modes, the signals input to the non-inverted input terminals of the first and second amplifier circuits are DC signals to stabilize the on-resistance linearity of the switches in the audio input circuit and to avoid the deterioration of THD of the audio input circuit.

Description

Technical Field

[0001] This invention relates to an audio input circuit, and more particularly to an audio input circuit that can avoid the deterioration of total harmonic distortion. Background Technology

[0002] Figure 1 Show a known microphone signal input circuit. Figure 1 The microphone signal input circuit 10 can operate in one of three modes via a switch: a single-ended mode, a differential mode, and a mixed-signal mode.

[0003] like Figure 1 As shown, the microphone signal input circuit 10 includes: a first path consisting of a first resistor 112 and a first switch 114, used to conduct in a single-ended mode and a mixed-signal mode to receive a single-ended signal VP2; a second path consisting of a second resistor 122 and a second switch 124, used to conduct in the single-ended mode and the mixed-signal mode to receive a DC signal VDC; a third path consisting of a third resistor 132 and a third switch 134, used to conduct in a differential mode and the mixed-signal mode to receive a positive component VP1 of a differential signal; and a fourth path consisting of a fourth resistor 142 and a fourth switch 144, used to conduct in the differential mode and the mixed-signal mode... The differential signal is received via a negative component VN1; an amplifier 150 having an inverting input, a non-inverting input, an inverting output, and a non-inverting output, wherein the inverting input is coupled to a first switch 114 and a third switch 134 to receive VP2 and / or VP1, the non-inverting input is coupled to a second switch 124 and a fourth switch 144 to receive VDC and / or VN1, the inverting output is used to output an inverted output signal VN, and the non-inverting output is used to output a non-inverting output signal VP; a first feedback resistor 160 is coupled between the inverting input and the inverting output; and a second feedback resistor 170 is coupled between the non-inverting input and the non-inverting output. It is worth noting that the initial resistance values ​​of the first resistor 112 and the second resistor 122 are... Figure 1 The resistance value is half of the initial resistance value of the other resistors.

[0004] Figure 2 This indicates that the microphone signal input circuit 10 is operating in single-ended mode, where the dashed arrow indicates the signal direction and the dashed sine wave indicates the signal. For example... Figure 2As shown, in this single-ended mode, to achieve VN and VP, both the inverting and non-inverting inputs of amplifier 150 will have signal components. This reduces the linearity of the on-resistance Ron of the first switch 114 and the second switch 124, thereby worsening the total harmonic distortion (THD) of the microphone signal input circuit 10. A similar problem exists in this mixed-signal mode.

[0005] based on Figure 1 The architecture of the microphone signal input circuit 10 also includes the following problems:

[0006] In this single-ended mode, if the gain of amplifier 150 is changed by adjusting the resistance value of the first feedback resistor 160, the input resistance Rin of the microphone signal input circuit 10 will change with the resistance value of the first feedback resistor 160 because there are signal components at the non-inverting and inverting input terminals of amplifier 150. Since this first path typically includes an AC coupling capacitor (not shown in the figure), the change in Rin means that the frequency response of this first path will change with the gain of amplifier 150, which will cause a change in the input frequency response of the microphone signal input circuit 10. A similar problem exists in the mixed-signal mode.

[0007] In this single-ended mode, the output offset of amplifier 150 (i.e., the difference between VP and VN) is related to the second resistor 122 and the first feedback resistor 160, and thus varies with the gain of amplifier 150, which degrades the output quality of microphone signal input circuit 10. A similar problem exists in mixed-signal mode. Summary of the Invention

[0008] One of the purposes of this disclosure is to provide an audio input circuit that avoids the problems of prior art.

[0009] A first embodiment of the audio input circuit disclosed herein can selectively operate in one of a single-ended mode and a differential mode. This first embodiment includes a single-ended signal input circuit, a differential signal input circuit, a first amplifier circuit, and a second amplifier circuit.

[0010] In this first embodiment, the single-ended signal input circuit includes: a first resistor of a single-ended circuit coupled between a single-ended audio input terminal and a first switch of a single-ended circuit, wherein the single-ended audio input terminal is used to receive a single-ended audio signal in the single-ended mode; the first switch of the single-ended circuit coupled between the first resistor of the single-ended circuit and a first inverting input terminal of a first amplifier, used to be turned on in the single-ended mode; and a second switch of a single-ended circuit coupled between a common-mode signal input terminal and a first non-inverting input terminal of the first amplifier, used to be turned on in the single-ended mode, wherein the common-mode signal input terminal is used to receive a common-mode signal.

[0011] In this first embodiment, the differential signal input circuit includes: a first differential circuit resistor coupled between a positive differential audio input terminal and a first differential circuit switch, wherein the positive differential audio input terminal is used to receive a positive terminal signal of a differential audio signal in the differential mode; the first differential circuit switch coupled between the first differential circuit resistor and the first inverting input terminal of the first amplifier, used to be turned on in the differential mode; a second differential circuit resistor coupled between a negative differential audio input terminal and a second differential circuit switch, wherein the negative differential audio input terminal is used to receive a negative terminal signal of the differential audio signal in the differential mode, and the negative terminal signal is complementary to the positive terminal signal; the second differential circuit switch coupled between the second differential circuit resistor and a third differential circuit switch, used to be turned on in the differential mode; and the third differential circuit switch coupled between the second differential circuit switch and the first non-inverting input terminal of the first amplifier, used to be turned on in the differential mode.

[0012] In this first embodiment, the first amplifier circuit includes: the first amplifier, which includes the first inverting input terminal, the first non-inverting input terminal and a first output terminal, wherein the first output terminal is used to output an inverted audio output signal based on the signals received by the first inverting input terminal and the first non-inverting input terminal; and a first feedback resistor coupled between the first inverting input terminal and the first output terminal. In this first embodiment, the second amplifier circuit includes: an input resistor coupled between the first output terminal and a second inverting input terminal of the second amplifier; a second feedback resistor, one end of which is coupled between the input resistor and the second inverting input terminal, and the other end of which is coupled between a second output terminal of the second amplifier and an output resistor; the second amplifier including the second inverting input terminal, a second non-inverting input terminal, and a second output terminal, wherein the second non-inverting input terminal is used to receive the common-mode signal, and the second output terminal is used to output a non-inverting audio output signal based on the signals received by the second inverting input terminal and the second non-inverting input terminal; and an output resistor, one end of which is coupled to the second output terminal, and the other end of which is coupled to the second switch of the differential circuit and the third switch of the differential circuit. It is worth noting that in this differential mode, the output of the second output terminal of the second amplifier cancels out the output of the second switch of the differential circuit through the output resistor, so that the first non-inverting input terminal receives a DC signal; therefore, the audio input circuit of the first embodiment can stabilize the linearity of the on-resistance of the switch coupled to the first non-inverting input terminal of the first amplifier in both single-ended and differential modes, so as to avoid the deterioration of the total harmonic distortion of the audio input circuit.

[0013] A second embodiment of the audio input circuit disclosed herein operates in a differential mode and includes the differential signal input circuit, the first amplifier circuit, and the second amplifier circuit of the aforementioned first embodiment, but the switches in the circuit may be replaced by transmission lines or fixed in a conducting state.

[0014] A third embodiment of the audio input circuit disclosed herein operates in a mixed-signal mode and includes the single-ended signal input circuit, the differential signal input circuit, the first amplifier circuit, and the second amplifier circuit of the first embodiment described above. However, the second switch of the single-ended circuit in the above circuit can be removed or fixed in a non-conducting state, and other switches can be replaced by transmission lines or fixed in a conducting state. In this third embodiment, the single-ended signal input circuit further includes: a second resistor of the single-ended circuit coupled between the common-mode signal input terminal and the first non-inverting input terminal of the first amplifier, wherein the common-mode signal input terminal is used to receive the common-mode signal.

[0015] The features, implementation, and effects of this invention are described in detail below with reference to the accompanying drawings, showing preferred embodiments. Attached Figure Description

[0016] [ Figure 1 [Displays a known microphone signal input circuit;]

[0017] [ Figure 2 ]show Figure 1 The microphone signal input circuit operates in a single-ended mode;

[0018] [ Figure 3 This invention illustrates an embodiment of the audio input circuit of the present invention.

[0019] [ Figure 4 ]show Figure 3 The audio input circuit operates in a single-ended mode;

[0020] [ Figure 5 ]show Figure 3 The audio input circuit operates in a differential mode;

[0021] [ Figure 6 [This shows another embodiment of the audio input circuit of the present invention, which can operate in a mixed signal mode;]

[0022] [ Figure 7 ]show Figure 3 A simplified circuit for the audio input circuit can operate in a single-ended mode; and

[0023] [ Figure 8 ]show Figure 3 A simplified circuit for the audio input circuit can operate in a differential mode. Detailed Implementation

[0024] This specification discloses an audio input circuit. The architecture of this audio input circuit can stabilize the linearity of the on-resistance of the switches in the audio input circuit to avoid the deterioration of the total harmonic distortion of the audio input circuit; the audio input circuit can also prevent its input resistance Rin and output offset from changing with the gain of the amplifier of the audio input circuit.

[0025] Figure 3 This invention illustrates an embodiment of the audio input circuit. Figure 3The audio input circuit 300 includes a single-ended signal input circuit 310, a differential signal input circuit 320, a first amplifier circuit 330, and a second amplifier circuit 340. The single-ended signal input circuit 310 is activated in a single-ended mode via a switch to output a signal to the first amplifier circuit 330. The differential signal input circuit 320 is activated in a differential mode via a switch to output a signal to the first amplifier circuit 330. The first amplifier circuit 330 outputs an inverted audio output signal VON to the second amplifier circuit 340 based on the received signal. The second amplifier circuit 340 outputs a non-inverted audio output signal VOP based on the received signal. It is worth noting that in both single-ended and differential modes, the signals received by the non-inverting input nodes of the first amplifier circuit 330 and the second amplifier circuit 340 are DC signals, without any changes, in order to stabilize the linearity of the on-resistance of the switches in the audio input circuit 300 and to avoid the deterioration of the total harmonic distortion (THD) of the audio input circuit 300.

[0026] See Figure 3 The single-ended signal input circuit 310 includes a first single-ended resistor 312, a first single-ended switch 314, and a second single-ended switch 316. The first single-ended resistor 312 is coupled between a single-ended audio input terminal and the first single-ended switch 314, wherein the single-ended audio input terminal is used to receive a single-ended audio signal VIP2 in this single-ended mode. The first single-ended switch 314 is coupled between the first single-ended resistor 312 and a first inverting input node of a first amplifier 332, and is used to turn on in this single-ended mode. The second single-ended switch 316 is coupled between a common-mode signal input terminal and a first non-inverting input terminal of the first amplifier 332, and is used to turn on in this single-ended mode, wherein the common-mode signal input terminal is used to receive a common-mode signal VCM. Figure 4 The audio input circuit 300 in this single-ended mode is shown for clarity; details are provided below.

[0027] See Figure 3The differential signal input circuit 320 includes a first differential resistor 322, a first differential switch 324, a second differential resistor 326, a second differential switch 328, and a third differential switch 329. The first differential resistor 322 is coupled between a positive differential audio input terminal and the first differential switch 324, wherein the positive differential audio input terminal is used to receive a positive terminal signal VIP1 of a differential audio signal in the differential mode. The first differential switch 324 is coupled between the first differential resistor 322 and the first inverting input terminal of the first amplifier 332, and is used to turn on in the differential mode. The second differential resistor 326 is coupled between a negative differential audio input terminal and the second differential switch 328, wherein the negative differential audio input terminal is used to receive a negative terminal signal VIN1 of the differential audio signal in the differential mode, and the negative terminal signal VIN1 is complementary to the positive terminal signal VIP1. The second differential switch 328 is coupled between the second differential resistor 326 and the third differential switch 329, and is used to turn on in this differential mode. The third differential switch 329 is coupled between the second differential switch 328 and the first non-inverting input terminal of the first amplifier 332, and is used to turn on in this differential mode. Figure 5 The audio input circuit 300 shown in this differential mode is for illustrative purposes; details are provided below.

[0028] See Figure 3 The first amplifier circuit 330 includes a first amplifier 332 and a first feedback resistor 334. The first amplifier 332 includes a first inverting input, a first non-inverting input, and a first output, wherein the first output is used to output an inverted audio output signal VON based on the signals received by the first inverting input and the first non-inverting input. The first feedback resistor 334 is coupled between the first inverting input and the first output.

[0029] See Figure 3The second amplifier circuit 340 includes an input resistor 342, a second feedback resistor 344, a second amplifier 346, and an output resistor 348. The input resistor 342 is coupled between the first output terminal of the first amplifier 332 and a second inverting input terminal of the second amplifier 346. One end of the second feedback resistor 344 is coupled between the input resistor 342 and the second inverting input terminal, and the other end of the second feedback resistor 344 is coupled between a second output terminal of the second amplifier 346 and the output resistor 348. The second amplifier 346 includes the second inverting input terminal, a second non-inverting input terminal, and a second output terminal. The second non-inverting input terminal is used to receive the common-mode signal VCM, and the second output terminal is used to output a non-inverting audio output signal VOP based on the signals received by the second inverting input terminal and the second non-inverting input terminal. One end of the output resistor 348 is coupled to the second output terminal, and the other end of the output resistor 348 is coupled to the second differential switch 328 and the third differential switch 329.

[0030] Figure 4 This indicates that the audio input circuit 300 is operating in this single-ended mode. Figure 4 As can be seen, the non-inverting inputs of both the first amplifier 332 and the second amplifier 346 receive the common-mode signal VCM. Therefore, the on-resistance Ron of the second switch 316 in the single-ended circuit does not bear the signal component, and thus there is no problem of reduced linearity of the on-resistance Ron. Consequently, the total harmonic distortion of the audio input circuit 300 is better in this single-ended mode compared to the prior art. In addition, since the VCM received by the non-inverting input of the first amplifier 332 is a constant, the input resistance Rin observed from the viewpoint of the first amplifier 332 does not change with the gain of the first amplifier circuit 330, that is, it does not change with the resistance value of the first feedback resistor 334. Furthermore, each input signal VIP2, VIP1, and VIN1 is a signal through an AC coupling capacitor (not shown in the figure). Under the AC coupling input of this capacitor, since the difference between the positive-phase audio output signal VOP (equivalent to -vos, where vos is equivalent to the signal at the inverting input terminal of the first amplifier 332) and the inverting audio output signal VON (equivalent to vos) (i.e., -2vos) is a constant value, the output offset of the audio input circuit 300 (i.e., the difference between VOP and VON) does not change with the gain of the first amplifier circuit 330, that is, it does not change with the resistance value of the first feedback resistor 334.

[0031] Figure 5 This indicates that the audio input circuit 300 is operating in this differential mode. Figure 5It can be seen that the output of the second output terminal of the second amplifier 346 cancels out the output of the second switch 328 of the differential circuit via the output resistor 348. This ensures that the on-resistance Ron of the third switch 329 of the differential circuit is not affected by signal components (i.e., the signal received by the first non-inverting input terminal of the first amplifier 332 is a DC signal), thus avoiding the problem of reduced linearity of the on-resistance Ron. In addition, since the signal received by the non-inverting input terminal of the first amplifier 332 is a DC signal, the input resistance Rin observed from the viewpoint of the first amplifier 332 does not change with the gain of the first amplifier circuit 330, that is, it does not change with the resistance value of the first feedback resistor 334.

[0032] In one implementation example of the audio input circuit 300, the audio input circuit 300 may optionally include some or all of the following technical features:

[0033] In either the single-ended or differential mode, the first resistor 312 of the single-ended circuit, the first resistor 322 of the differential circuit, the second resistor 326 of the differential circuit, the first feedback resistor 334, and the output resistor 348 have the same resistance value.

[0034] Each of the single-ended circuit first resistor 312, the differential circuit first resistor 322, the differential circuit second resistor 326, the first feedback resistor 334, and the output resistor 348 is an adjustable resistor.

[0035] The input resistor 342 and the second feedback resistor 344 have the same resistance value;

[0036] When the single-ended mode is enabled, the differential mode is disabled, and the first differential switch 324, the second differential switch 328, and the third differential switch 329 are not connected; and when the differential mode is enabled, the single-ended mode is disabled, and the first single-ended switch 314 and the second single-ended switch 316 are not connected.

[0037] Each of the single-ended audio signal and the differential audio signal is a microphone input signal; and

[0038] The audio input circuit 300 is used in an audio codec.

[0039] Figure 6 This illustrates another embodiment of the audio input circuit of the present invention. Compared to Figure 3 , Figure 6The single-ended signal input circuit 310 of the audio input circuit 600 further includes a second single-ended resistor 610 and a third single-ended switch 620. The second single-ended resistor 610 is coupled between the common-mode signal input terminal and the third single-ended switch 620. The third single-ended switch 620 is coupled between the second single-ended resistor 610 and the third differential switch 329, and is used to conduct in a mixed-signal mode. In this mixed-signal mode, the first single-ended switch 314, the third single-ended switch 620, the first differential switch 324, the second differential switch 328, and the third differential switch 329 are all turned on, while the second single-ended switch 316 is not turned on. Figure 6 When the audio input circuit 600 is used only in the mixed signal mode, the second switch 316 of the single-ended circuit can be removed or fixed in a non-conducting state, and other switches can be replaced by transmission lines or fixed in a conducting state.

[0040] In one embodiment of the audio input circuit 600, the audio input circuit 600 includes the following technical features: in the mixed-signal mode, each of the single-ended circuit first resistor 312 and the single-ended circuit second resistor 610 has a first resistance value, and each of the differential circuit first resistor 322, the differential circuit second resistor 326, the first feedback resistor 324, and the output resistor 348 has a second resistance value, the first resistance value being half of the second resistance value. Where feasible, the above technical features are not intended to limit the implementation of this invention.

[0041] when Figure 3 When the audio input circuit 300 is only used in this single-ended mode, the audio input circuit 300 can be simplified to Figure 7 The audio input circuit 700 includes a single-ended circuit first switch 314 and a single-ended circuit second switch 316 fixed in a conducting state. Where feasible, the audio input circuit 700 can be simplified in other ways; for example, both the single-ended circuit first switch 314 and the single-ended circuit second switch 316 can be replaced by transmission lines.

[0042] This technical field is accessible to those with general knowledge. Figures 3-6 To understand from the description of the embodiments Figure 7 Details and variations of the embodiments, as well as repetitive and redundant descriptions, are omitted here.

[0043] when Figure 3 When the audio input circuit 300 is only used to operate in this differential mode, the audio input circuit 300 can be simplified to Figure 8The audio input circuit 800 includes a differential circuit with first switch 324, second switch 328, and third switch 329 fixed in a conducting state. Where feasible, the audio input circuit 800 can be simplified in other ways; for example, the differential circuit with first switch 324, second switch 328, and third switch 329 can all be replaced by transmission lines.

[0044] This technical field is accessible to those with general knowledge. Figures 3-6 To understand from the description of the embodiments Figure 8 Details and variations of the embodiments, as well as repetitive and redundant descriptions, are omitted here.

[0045] Please note that, where implementation is possible, those skilled in the art may selectively use some or all of the technical features in any of the foregoing embodiments, or selectively use a combination of some or all of the technical features in the foregoing multiple embodiments, to implement the present invention; in other words, the implementation of the present invention is flexible.

[0046] In summary, the audio input circuit disclosed herein can avoid the reduction in the linearity of the on-resistance of the switches in the audio input circuit, thereby avoiding the deterioration of the total harmonic distortion of the audio input circuit; the audio input circuit can also avoid its input resistance Rin and output offset changing with the gain of the amplifier of the audio input circuit.

[0047] Although the embodiments of the present invention have been described above, these embodiments are not intended to limit the present invention. Those skilled in the art can make changes to the technical features of the present invention based on the explicit or implicit content of the present invention. All such changes may fall within the scope of patent protection sought by the present invention. In other words, the scope of patent protection of the present invention shall be determined by the scope of the patent application in this specification.

[0048] [Symbol Explanation]

[0049] 10: Microphone signal input circuit

[0050] 112: First resistor

[0051] 114: First Switch

[0052] 122: Second resistor

[0053] 124: Second Switch

[0054] 132: Third resistor

[0055] 134: Third Switch

[0056] 142: Fourth resistor

[0057] 144: Fourth Switch

[0058] 150: Amplifier

[0059] 160: First feedback resistor

[0060] 170: Second feedback resistor

[0061] VP2: Single-ended signal

[0062] VDC: DC signal

[0063] VP1: One positive terminal component of the differential signal

[0064] VN1: The negative component of the differential signal

[0065] VN: Inverting output signal

[0066] VP: Non-inverting output signal

[0067] 300: Audio Input Circuit

[0068] 310: Single-ended signal input circuit

[0069] 320: Differential signal input circuit

[0070] 330: First Amplifier Circuit

[0071] 340: Second Amplifier Circuit

[0072] 312: First resistor in a single-ended circuit

[0073] 314: First switch in a single-ended circuit

[0074] 316: Second switch in single-ended circuit

[0075] 322: First resistor in differential circuit

[0076] 324: First switch of differential circuit

[0077] 326: Second resistor in differential circuit

[0078] 328: Second switch of differential circuit

[0079] 329: Third switch in differential circuit

[0080] 332: First Amplifier

[0081] 334: First feedback resistor

[0082] 342: Input resistance

[0083] 344: Second feedback resistor

[0084] 346: Second Amplifier

[0085] 348: Output resistor

[0086] VIP2: Single-ended audio signal

[0087] VCM: Common-mode signal

[0088] VIP1: One positive terminal signal of the differential audio signal

[0089] VIN1: The negative terminal signal of the differential audio signal

[0090] VON: Inverted audio output signal

[0091] VOP: Positive phase audio output signal

[0092] 600: Audio Input Circuit

[0093] 610: Second resistor in a single-ended circuit

[0094] 620: Third switch in single-ended circuit

[0095] 700: Audio Input Circuit

[0096] 800: Audio input circuit.

Claims

1. An audio input circuit, comprising: A single-ended signal input circuit, comprising: A first resistor in a single-ended circuit is coupled between a single-ended audio input terminal and a first switch in a single-ended circuit, wherein... This single-ended audio input is used to receive a single-ended audio signal in a single-ended mode; The first switch of the single-ended circuit is coupled between the first resistor of the single-ended circuit and a first inverting input terminal of a first amplifier, and is used to turn on in the single-ended mode. as well as A second switch of a single-ended circuit is coupled between a common-mode signal input terminal and a first non-inverting input terminal of the first amplifier, and is used to turn on in the single-ended mode, wherein the common-mode signal input terminal is used to receive a common-mode signal. A differential signal input circuit includes: A first resistor of a differential circuit is coupled between a positive input terminal of a differential audio circuit and a first switch of a differential circuit, wherein the positive input terminal of the differential audio circuit is used to receive a positive terminal signal of a differential audio signal in a differential mode. The first switch of the differential circuit is coupled between the first resistor of the differential circuit and the first inverting input terminal of the first amplifier, and is used to turn on in the differential mode. A second resistor of a differential circuit is coupled between a negative input terminal of a differential audio circuit and a second switch of a differential circuit, wherein the negative input terminal of the differential audio circuit is used to receive a negative signal of the differential audio signal in the differential mode, and the negative signal is complementary to the positive signal. The second switch of the differential circuit is coupled between the second resistor of the differential circuit and a third switch of the differential circuit, and is used to turn on in the differential mode; and The third switch of the differential circuit is coupled between the second switch of the differential circuit and the first non-inverting input terminal of the first amplifier, and is used to turn on in the differential mode. A first amplifier circuit, comprising: The first amplifier includes a first inverting input terminal, a first non-inverting input terminal, and a first output terminal, wherein the first output terminal is used to output an inverted audio output signal based on the signals received by the first inverting input terminal and the first non-inverting input terminal; and A first feedback resistor is coupled between the first inverting input terminal and the first output terminal; and A second amplifier circuit, comprising: An input resistor is coupled between the first output terminal and a second inverting input terminal of a second amplifier; A second feedback resistor, one end of which is coupled between the input resistor and the second inverting input terminal, and the other end of which is coupled between a second output terminal of the second amplifier and an output resistor; The second amplifier includes a second inverting input, a second non-inverting input, and a second output. The second non-inverting input receives the common-mode signal, and the second output outputs a non-inverting audio output signal based on the signals received by the second inverting input and the second non-inverting input. The output resistor has one end coupled to the second output terminal and the other end coupled to the second switch and the third switch of the differential circuit. In this differential mode, one output of the second output terminal cancels out one output of the second switch of the differential circuit via the output resistor, so that the first non-inverting input terminal receives a DC signal.

2. The audio input circuit as described in claim 1, wherein, In either the single-ended mode or the differential mode, the first resistor of the single-ended circuit, the first resistor of the differential circuit, the second resistor of the differential circuit, the first feedback resistor, and the output resistor have the same resistance value.

3. The audio input circuit as described in claim 1, wherein, The input resistor has the same resistance value as the second feedback resistor.

4. The audio input circuit as described in claim 1, wherein: When the single-ended mode is enabled, the differential mode is disabled, and the first switch, the second switch, and the third switch of the differential circuit are not connected. as well as When the differential mode is enabled, the single-ended mode is disabled, and the first switch and the second switch of the single-ended circuit are not connected.

5. The audio input circuit as described in claim 1, wherein, The single-ended signal input circuit further includes: A second resistor of a single-ended circuit is coupled between the common-mode signal input terminal and a third switch of a single-ended circuit; The third switch of the single-ended circuit is coupled between the second resistor of the single-ended circuit and the third switch of the differential circuit, and is used to turn on in a mixed-signal mode. In the mixed signal mode, the first switch of the single-ended circuit, the first switch of the differential circuit, the second switch of the differential circuit, and the third switch of the differential circuit are turned on, while the second switch of the single-ended circuit is not turned on.

6. The audio input circuit as described in claim 5, wherein, In the mixed signal mode, each of the first resistor and the second resistor of the single-ended circuit has a first resistance value, and each of the first resistor, the second resistor, the first feedback resistor, and the output resistor has a second resistance value, wherein the first resistance value is half of the second resistance value.

7. An audio input circuit, the audio input circuit operating in a differential mode, and comprising: A differential signal input circuit includes: The first resistor in a differential circuit, wherein, The first resistor of the differential circuit is coupled between a differential audio positive input terminal and a first inverting input terminal of a first amplifier. The differential audio positive input terminal is used to receive a positive terminal signal of a differential audio signal. as well as A second resistor in a differential circuit, wherein the second resistor in the differential circuit is coupled between a differential audio negative input terminal and a first non-inverting input terminal of the first amplifier, the differential audio negative input terminal is used to receive a negative terminal signal of the differential audio signal, the negative terminal signal and the positive terminal signal are complementary; A first amplifier circuit, comprising: The first amplifier includes a first inverting input terminal, a first non-inverting input terminal, and a first output terminal, wherein the first output terminal is used to output an inverted audio output signal based on the signals received by the first inverting input terminal and the first non-inverting input terminal; and A first feedback resistor is coupled between the first inverting input terminal and the first output terminal; and A second amplifier circuit, comprising: An input resistor is coupled between the first output terminal and a second inverting input terminal of a second amplifier; A second feedback resistor, one end of which is coupled between the input resistor and the second inverting input terminal, and the other end of which is coupled between a second output terminal of the second amplifier and an output resistor; The second amplifier includes a second inverting input, a second non-inverting input, and a second output. The second non-inverting input receives a common-mode signal, and the second output outputs a non-inverting audio output signal based on the signals received by the second inverting input and the second non-inverting input. The output resistor has one end coupled to the second output terminal, and the other end coupled to the second resistor of the differential circuit and the first non-inverting input terminal of the first amplifier. In this circuit, one output of the second output terminal cancels out one output of the second resistor of the differential circuit via the output resistor, so that the first non-inverting input terminal receives a DC signal.

8. The audio input circuit as described in claim 7, wherein, The first resistor, the second resistor, the first feedback resistor, and the output resistor of the differential circuit have the same resistance value.

9. An audio input circuit, the audio input circuit operating in a mixed-signal mode, and comprising: A single-ended signal input circuit, comprising: A first resistor in a single-ended circuit is coupled between a single-ended audio input terminal and a first inverting input terminal of a first amplifier, wherein... This single-ended audio input is used to receive a single-ended audio signal; as well as A second resistor of a single-ended circuit is coupled between a common-mode signal input terminal and a first non-inverting input terminal of the first amplifier, wherein the common-mode signal input terminal is used to receive a common-mode signal; A differential signal input circuit includes: A first resistor in a differential circuit is coupled between a positive input terminal of a differential audio signal and a first inverting input terminal of a first amplifier, wherein the positive input terminal of the differential audio signal is used to receive a positive signal from a differential audio signal; and A second resistor in a differential circuit is coupled between a differential audio negative input terminal and the first non-inverting input terminal of the first amplifier, wherein the differential audio negative input terminal is used to receive a negative signal of the differential audio signal, and the negative signal is complementary to the positive signal. A first amplifier circuit, comprising: The first amplifier includes a first inverting input terminal, a first non-inverting input terminal, and a first output terminal, wherein the first output terminal is used to output an inverted audio output signal based on the signals received by the first inverting input terminal and the first non-inverting input terminal; and A first feedback resistor is coupled between the first inverting input terminal and the first output terminal; and A second amplifier circuit, comprising: An input resistor is coupled between the first output terminal and a second inverting input terminal of a second amplifier; A second feedback resistor, one end of which is coupled between the input resistor and the second inverting input terminal, and the other end of which is coupled between a second output terminal of the second amplifier and an output resistor; The second amplifier includes a second inverting input, a second non-inverting input, and a second output. The second non-inverting input receives the common-mode signal, and the second output outputs a non-inverting audio output signal based on the signals received by the second inverting input and the second non-inverting input. The output resistor has one end coupled to the second output terminal and the other end coupled to the second resistor of the single-ended circuit, the second resistor of the differential circuit, and the first non-inverting input terminal of the first amplifier.

10. The audio input circuit as claimed in claim 9, wherein, Each of the first resistor and the second resistor in the single-ended circuit has a first resistance value, and each of the first resistor, the second resistor, the first feedback resistor, and the output resistor in the differential circuit has a second resistance value, wherein the first resistance value is half of the second resistance value.

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