A microphone amplifier circuit and audio device

Abstract

The application discloses a microphone amplifier circuit, which comprises a microphone input interface module, a switching tube amplification circuit and an operational amplifier circuit; the input end of the microphone input interface module is used for being connected with a microphone jack; the output end of the microphone input interface module is connected with the switching tube amplification circuit and the operational amplifier circuit respectively, and is used for conveying input audio signals to the input end of the switching tube amplification circuit and the input end of the operational amplifier circuit respectively; the output end of the switching tube amplification circuit is connected with the input end of the operational amplifier circuit, and is used for amplifying received audio signals in multiple stages and outputting the audio signals to the operational amplifier circuit; and the output end of the operational amplifier circuit is connected with a subsequent power amplifier circuit, and is used for amplifying received audio signals and outputting the audio signals to the subsequent power amplifier circuit. The application further discloses an audio device. The application can guarantee good audio noise processing effect and audio quality effect, thereby improving audio noise processing stability, and has low circuit cost.

Description

Technical Field

[0001] This invention relates to the field of audio equipment technology, and more particularly to a microphone amplifier circuit and an audio device. Background Technology

[0002] In current audio equipment, microphone amplifier circuits are typically connected to power amplifier circuits. These microphone amplifier circuits generally use a pre-amplifier circuit to process the audio signal input from the microphone to improve the signal-to-noise ratio (SNR) of the output signal. The signal is then amplified by the pre-amplifier circuit before being output to the power amplifier circuit, thereby reducing audio noise and improving audio quality. However, pre-amplifier circuits are susceptible to common-mode interference from the microphone, which can reduce the SNR of the output signal, affecting the audio noise processing effect and audio quality, thus impacting the stability of audio noise processing. Furthermore, these circuits are relatively expensive.

[0003] In addition, existing microphone amplifier circuits are only suitable for one type of fixed microphone application and cannot be switched to be suitable for dynamic or condenser microphone applications, resulting in a narrow range of compatibility and failing to meet user needs. Summary of the Invention

[0004] The technical problem to be solved by the present invention is to provide a microphone amplifier circuit and audio device that can stably improve the signal-to-noise ratio of the output audio signal, ensure good audio noise processing effect and audio sound quality, thereby improving the stability of audio noise processing, and the circuit cost is low.

[0005] To address the aforementioned technical problems, this invention provides a microphone amplifier circuit, comprising a microphone input interface module, a switching transistor amplifier circuit, and an operational amplifier circuit. The input terminal of the microphone input interface module is connected to a microphone jack, and the output terminal of the microphone input interface module is connected to both the switching transistor amplifier circuit and the operational amplifier circuit, respectively, to transmit the input audio signal to the input terminals of the switching transistor amplifier circuit and the operational amplifier circuit. The output terminal of the switching transistor amplifier circuit is connected to the input terminal of the operational amplifier circuit, to amplify the received audio signal through multiple stages and output it to the operational amplifier circuit. The output terminal of the operational amplifier circuit is connected to a subsequent power amplifier circuit, to amplify the received audio signal and output it to the subsequent power amplifier circuit.

[0006] As an improvement to the above solution, the switching transistor amplifier circuit includes a first transistor, a second transistor, a first resistor, a second resistor, a third resistor, a fourth resistor, and a first capacitor; the first signal output terminal of the microphone input interface module is connected to the base of the first transistor and is connected to one end of the second resistor through the first capacitor and the first resistor, respectively, and the other end of the second resistor is connected to the first power supply voltage; the emitter of the first transistor is grounded and connected to the base of the first transistor through the third resistor, and the collector of the first transistor is connected to the base of the second transistor; the base of the second transistor is connected to the emitter of the second transistor through the fourth resistor, the emitter of the second transistor is connected to the first power supply voltage through the second resistor and is connected to the second signal output terminal of the microphone input interface module and the input terminal of the operational amplifier circuit, respectively, and the collector of the second transistor is grounded.

[0007] As an improvement to the above scheme, the switching transistor amplifier circuit also includes an energy storage circuit, which includes an energy storage capacitor and a second capacitor; one end of the energy storage capacitor is connected to the first power supply voltage, the other end of the energy storage capacitor is grounded, and the second capacitor is connected in parallel with the energy storage capacitor.

[0008] As an improvement to the above scheme, the operational amplifier circuit includes an operational amplifier, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a third capacitor, and a fourth capacitor. The inverting input terminal of the operational amplifier is connected to the output terminal of the switching transistor amplifier circuit and the second signal output terminal of the microphone input interface module through the fifth resistor. The inverting input terminal of the operational amplifier is also connected to the output terminal of the operational amplifier through the sixth resistor and the third capacitor. The output terminal of the operational amplifier is connected to the subsequent power amplifier circuit. The non-inverting input terminal of the operational amplifier is connected to the second power supply voltage through the seventh resistor and grounded through the eighth resistor. The fourth capacitor is connected in parallel with the eighth resistor.

[0009] As an improvement to the above solution, a microphone switching circuit and a main control chip are also included. The output of the microphone switching circuit is connected to the microphone input interface module and the switching transistor amplifier circuit; the main control chip is connected to the input of the microphone switching circuit and is used to control the power supply status of the microphone switching circuit.

[0010] As an improvement to the above solution, the microphone switching circuit includes a switching circuit, a third transistor, a ninth resistor, a tenth resistor, an eleventh resistor, and a first diode. The emitter of the third transistor is connected to the first power supply voltage through the ninth resistor and is also connected to the cathode of the first diode and one end of the tenth resistor. The anode of the first diode is grounded, and the other end of the tenth resistor is connected to the base of the third transistor. The base of the third transistor is connected to the switching circuit, and the collector of the third transistor is connected to the first signal output terminal of the microphone input interface module through the eleventh resistor. The main control chip is connected to the switching circuit and is used to control the switching on and off of the third transistor through the switching circuit.

[0011] As an improvement to the above scheme, the switching circuit includes a fourth transistor, a fifth transistor, a twelfth resistor, and a thirteenth resistor; the collector of the fourth transistor is connected to the base of the third transistor, the emitter of the fourth transistor is grounded, the base of the fourth transistor is connected to the collector of the fifth transistor, the base of the fifth transistor is grounded through the twelfth resistor, and the emitter of the fifth transistor is connected to the main control chip through the thirteenth resistor.

[0012] As an improvement to the above scheme, the first transistor is an NPN transistor and the second transistor is a PNP transistor.

[0013] As an improvement to the above scheme, the third and fifth transistors are both PNP transistors, and the fourth transistor is an NPN transistor.

[0014] Accordingly, the present invention also provides an audio device, characterized in that it includes the above-described microphone amplifier circuit.

[0015] Implementing this invention has the following beneficial effects:

[0016] The microphone amplifier circuit and audio device of this invention are not affected by the common-mode interference signal of the microphone, can stably improve the signal-to-noise ratio of the output audio signal, ensure good audio noise processing effect and audio sound quality, thereby improving the stability of audio noise processing, and the circuit cost is low.

[0017] In addition, the present invention can control the power supply state of the microphone switching circuit through the main control chip to switch between applications suitable for dynamic microphones or condenser microphones, with a wide range of compatibility, which can meet the user's needs. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the first embodiment of the microphone amplifier circuit of the present invention;

[0019] Figure 2 This is a detailed circuit diagram of the first embodiment of the microphone amplifier circuit of the present invention;

[0020] Figure 3 This is a schematic diagram of the second embodiment of the microphone amplifier circuit of the present invention;

[0021] Figure 4 This is a detailed circuit diagram of the second embodiment of the microphone amplifier circuit of the present invention;

[0022] Figure 5 This is a schematic diagram of the structure of the audio device of the present invention. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings.

[0024] like Figure 1 As shown, Figure 1 The diagram shows a first embodiment of the microphone amplifier circuit of the present invention, including a microphone input interface module 1, a switching transistor amplifier circuit 2, and an operational amplifier circuit 3. The input terminal of the microphone input interface module 1 is connected to a microphone jack, and the output terminal of the microphone input interface module 1 is connected to the switching transistor amplifier circuit 2 and the operational amplifier circuit 3, respectively, for transmitting the input audio signal to the input terminal of the switching transistor amplifier circuit 2 and the input terminal of the operational amplifier circuit 3, respectively. The output terminal of the switching transistor amplifier circuit 2 is connected to the input terminal of the operational amplifier circuit 3, for amplifying the received audio signal through multiple stages and outputting it to the operational amplifier circuit 3. The output terminal of the operational amplifier circuit 3 is connected to the subsequent power amplifier circuit, for amplifying the received audio signal and outputting it to the subsequent power amplifier circuit.

[0025] By designing the microphone input interface module 1 and the switching transistor amplifier circuit 2, this circuit does not require the absolute symmetry of the two input terminals, unlike existing preamplifier circuits. Therefore, this invention does not introduce common-mode interference signals from the microphone and is unaffected by them. The switching transistor amplifier circuit 2 amplifies the received audio signal and outputs it with maximum undistorted performance, while also performing noise reduction. The operational amplifier circuit 3 processes the received audio signal to improve its driving capability and drive the subsequent power amplifier circuit for further audio processing. This invention can stably improve the signal-to-noise ratio of the output audio signal, ensuring good audio noise processing and sound quality, thereby improving the stability of audio noise processing, and the circuit cost is low.

[0026] The invention will now be described in further detail with reference to specific circuit diagrams:

[0027] like Figure 2 As shown, Figure 2 A detailed circuit diagram of the first embodiment of the microphone amplifier circuit of the present invention is shown. The microphone input interface module 1, the switching transistor amplifier circuit 2, and the operational amplifier circuit 3 are described below:

[0028] I. Microphone Input Interface Module 1

[0029] The microphone input interface module 1 includes a microphone input interface socket J1, which is used to insert a microphone into the jack and connect to the microphone for signal connection. Pins 1, 3 and 5 of the microphone input interface socket J1 are grounded, pin 4 of the microphone input interface socket J1 is the first signal output terminal, and pin 2 of the microphone input interface socket J1 is the second signal output terminal.

[0030] II. Switching transistor amplifier circuit 2

[0031] The switching transistor amplifier circuit 2 includes a first transistor N1, a second transistor P1, a first resistor R9, a second resistor R5, a third resistor R7, a fourth resistor R10, a fourteenth resistor R3, a fifteenth resistor R6, a first capacitor C19, a fifth capacitor C4, and a sixth capacitor C22.

[0032] The first signal output terminal of the microphone input interface module 1 is connected to one end of the fifth capacitor C4. The other end of the fifth capacitor C4 is connected to the base of the first transistor N1 and is connected to one end of the second resistor R5 through the first capacitor C19 and the first resistor R9. The other end of the second resistor R5 is connected to the first power supply voltage +12V. The first signal output terminal of the microphone input interface module 1 is grounded through the fourteenth resistor R3. The emitter of the first transistor N1 is connected to the base of the first transistor N1 through the fifteenth resistor R6 and the third resistor R7. The connection point between the fifteenth resistor R6 and the third resistor R7 is grounded. The collector of the first transistor N1 is connected to the base of the second transistor P1; the base of the second transistor P1 is connected to the emitter of the second transistor P1 through the fourth resistor R10; the emitter of the second transistor P1 is connected to the first power supply voltage +12V through the second resistor R5 and is connected to the second signal output terminal of the microphone input interface module 1 and the input terminal of the operational amplifier circuit 3 through the sixth capacitor C22; the collector of the second transistor P1 is grounded.

[0033] It should be noted that the audio signal output from the first signal output terminal of the microphone input interface module 1 is coupled to the base of the first transistor N1 via the fifth capacitor C4. The first resistor R9, the second resistor R5, and the third resistor R7 provide a bias voltage to the base of the first transistor N1, causing both the first transistor N1 and the second transistor P1 to conduct. Noise feedback is processed through the first capacitor C19, which also improves the dynamic response of the circuit. Both the first transistor N1 and the second transistor P1 amplify the signal, and the audio signal undergoes multi-stage amplification through the first transistor N1 and the second transistor P1 sequentially. The amplification factor can be changed by adjusting the resistance of the first resistor R9 and the second resistor R5.

[0034] To achieve maximum undistorted output of the audio signal, a suitable quiescent operating point needs to be set. In this embodiment, the emitter potential of the second transistor P1 is set to the midpoint of the power supply potential. That is, by adjusting the value of the second resistor R5, the emitter voltage of the second transistor P1 is made to 6V, thereby achieving maximum undistorted output of the audio signal. The switching transistor amplifier circuit 2 can stably improve the signal-to-noise ratio of the output audio signal, ensuring good audio noise processing effect and audio sound quality, thereby improving the stability of audio noise processing. Moreover, the circuit cost is lower than that of existing preamplifier circuits.

[0035] Preferably, the first transistor N1 is an NPN transistor, and the second transistor P1 is a PNP transistor.

[0036] Preferably, the switching transistor amplifier circuit 2 further includes an energy storage circuit 21, which includes an energy storage capacitor E1 and a second capacitor C3. One end of the energy storage capacitor E1 is connected to the first supply voltage +12V, and the other end of the energy storage capacitor E1 is grounded. The second capacitor C3 is connected in parallel with the energy storage capacitor E1. The function of the energy storage capacitor E1 is to provide energy to the subsequent circuits, ensuring sufficient output current at low frequencies so that the audio signal is output without distortion.

[0037] III. Operational Amplifier Circuit 3

[0038] The operational amplifier circuit 3 includes an operational amplifier U1, a fifth resistor R22, a sixth resistor R20, a seventh resistor R25, an eighth resistor R26, a sixteenth resistor R12, a seventeenth resistor R23, a third capacitor C10, a fourth capacitor C15, a seventh capacitor C13, and an eighth capacitor C14.

[0039] The inverting input of operational amplifier U1 is connected to the output of the switching transistor amplifier circuit 2 and the second signal output of the microphone input interface module 1 via the fifth resistor R22. The inverting input of operational amplifier U1 is also grounded via the fifth resistor R22 and the sixteenth resistor R12. The inverting input of operational amplifier U1 is also connected to the output of operational amplifier U1 via the sixth resistor R20 and the third capacitor C10. The output of operational amplifier U1 is connected to the subsequent power amplifier circuit via capacitor C12 and the seventeenth resistor R23. The non-inverting input of operational amplifier U1 is connected to the second supply voltage via the seventh resistor R25 and grounded via the eighth resistor R26. The fourth capacitor C15 is connected in parallel with the eighth resistor R26. The power supply terminal of operational amplifier U1 is connected to the second supply voltage (12V), one end of the seventh capacitor C13, and one end of the eighth capacitor C14. The ground terminal of operational amplifier U1 is grounded and connected to the other end of the seventh capacitor C13 and the other end of the eighth capacitor C14.

[0040] It should be noted that the operational amplifier U1 processes the audio signal output from the second signal output terminal of the microphone input interface module 1 and the audio signal output from the switching transistor amplifier circuit 2, and outputs the relevant audio signal to the subsequent power amplifier circuit. This can improve the driving capability of the output audio signal and facilitate driving the subsequent power amplifier circuit, which then performs subsequent audio processing.

[0041] Preferably, the operational amplifier U1 is a single-channel high-efficiency low-noise operational amplifier NE5534, but it is not limited to this and can be selected according to actual needs.

[0042] like Figure 3As shown, Figure 3 This diagram shows a second embodiment of the microphone amplifier circuit of the present invention. This embodiment is similar to... Figure 1 Unlike the first embodiment shown, this embodiment also includes a microphone switching circuit 4 and a main control chip 5.

[0043] The output of the microphone switching circuit 4 is connected to the microphone input interface module 1 and the switching transistor amplifier circuit 2; the main control chip 5 is connected to the input of the microphone switching circuit 4 and is used to control the power supply status of the microphone switching circuit 4. This invention can control the power supply status of the microphone switching circuit 4 through the main control chip 5 to switch between applications suitable for dynamic or condenser microphones, providing a wide range of compatibility and meeting user needs.

[0044] like Figure 4 As shown, Figure 4 This shows a detailed circuit diagram of a second embodiment of the microphone amplifier circuit of the present invention. This embodiment is similar to... Figure 2 Unlike the first embodiment shown, this embodiment also includes a microphone switching circuit 4.

[0045] The microphone switching circuit 4 includes a switch circuit 41, a third transistor P2, a ninth resistor R62, a tenth resistor R42, an eleventh resistor R1, and a first diode Z1. The emitter of the third transistor P2 is connected to the first supply voltage +12V through the ninth resistor R62 and is also connected to the cathode of the first diode Z1 and one end of the tenth resistor R42. The anode of the first diode Z1 is grounded. The other end of the tenth resistor R42 is connected to the base of the third transistor P2. The base of the third transistor P2 is connected to the switch circuit 41. The collector of the third transistor P2 is connected to the first signal output terminal of the microphone input interface module 1 through the eleventh resistor R1. The main control chip 5 is connected to the switch circuit 41 and is used to control the switching on and off of the third transistor P2 through the switch circuit 41.

[0046] It should be noted that when the microphone amplifier circuit needs to be adapted for condenser microphone applications, the main control chip 5 is controlled by an externally input control signal. This causes the main control chip 5 to control the third transistor P2 to conduct via the switching circuit 41, outputting a +12V0 power supply voltage. This voltage, through the eleventh resistor R1, acts as a pull-up resistor to the signal at the first signal output terminal of the microphone input interface module 1, thus meeting the inherent characteristics of condenser microphones and making it suitable for condenser microphone applications. When the microphone amplifier circuit needs to be adapted for dynamic microphone applications, the main control chip 5 is controlled by an externally input control signal. This causes the main control chip 5 to control the third transistor P2 to deactivate via the switching circuit 41. In this case, the +12V0 power supply voltage is not output, and the signal at the first signal output terminal of the microphone input interface module 1 is not pulled up. In this case, the microphone input interface module 1 is suitable for dynamic microphone applications. This invention can control the power supply state of the microphone switching circuit 4 via the main control chip 5 to switch between applications suitable for dynamic or condenser microphones, providing a wide range of compatibility and meeting user needs.

[0047] Specifically, the switching circuit 41 includes a fourth transistor N2, a fifth transistor P3, a twelfth resistor R71, a thirteenth resistor R67, and an eighteenth resistor R65. The collector of the fourth transistor N2 is connected to the base of the third transistor P2 through the eighteenth resistor R65. The emitter of the fourth transistor N2 is grounded. The base of the fourth transistor N2 is connected to the collector of the fifth transistor P3. The base of the fifth transistor P3 is grounded through the twelfth resistor R71. The emitter of the fifth transistor P3 is connected to the main control chip 5 through the thirteenth resistor R67.

[0048] It should be noted that the main control chip 5 outputs a control signal to control the on / off state of the fourth transistor N2 and the fifth transistor P3, thereby controlling the on / off state of the third transistor P2. This enables the main control chip 5 to control the power supply state of the microphone switching circuit 4, switching between applications suitable for dynamic microphones or condenser microphones. This provides a wide range of compatibility and can meet the needs of users.

[0049] Preferably, the third transistor P2 and the fifth transistor P3 are both PNP transistors, and the fourth transistor N2 is an NPN transistor. The main control chip is an MCU chip, and its specific model is not limited here.

[0050] like Figure 5 As shown, the present invention provides an audio device including the microphone amplifier circuit 6 described above. Since the microphone amplifier circuit 6 has the above-mentioned technical effects, the audio device 7 including the microphone amplifier circuit 6 should also have the above-mentioned technical effects, which will not be repeated here.

[0051] The above-disclosed embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of the present invention. Therefore, any equivalent variations made in accordance with the claims of the present invention are still within the scope of the present invention.

Claims

1. A microphone amplifier circuit, characterized in that, Includes a microphone input interface module, a switching transistor amplifier circuit, and an operational amplifier circuit; The input terminal of the microphone input interface module is used to connect to the microphone jack, and the output terminal of the microphone input interface module is connected to the switching transistor amplifier circuit and the operational amplifier circuit respectively, for transmitting the input audio signal to the input terminal of the switching transistor amplifier circuit and the input terminal of the operational amplifier circuit respectively. The output terminal of the switching transistor amplifier circuit is connected to the input terminal of the operational amplifier circuit, and is used to amplify the received audio signal in multiple stages and output it to the operational amplifier circuit. The output of the operational amplifier circuit is connected to the subsequent power amplifier circuit, and is used to amplify the received audio signal and output it to the subsequent power amplifier circuit. The switching transistor amplifier circuit includes a first transistor, a second transistor, a first resistor, a second resistor, a third resistor, a fourth resistor, and a first capacitor. The first signal output terminal of the microphone input interface module is connected to the base of the first transistor and is connected to one end of the second resistor through the first capacitor and the first resistor, respectively. The other end of the second resistor is connected to the first power supply voltage. The emitter of the first transistor is grounded and connected to the base of the first transistor through the third resistor. The collector of the first transistor is connected to the base of the second transistor. The base of the second transistor is connected to the emitter of the second transistor through the fourth resistor. The emitter of the second transistor is connected to the first power supply voltage through the second resistor and is connected to the second signal output terminal of the microphone input interface module and the input terminal of the operational amplifier circuit, respectively. The collector of the second transistor is grounded.

2. The microphone amplifier circuit according to claim 1, characterized in that, The switching transistor amplifier circuit also includes an energy storage circuit, which includes an energy storage capacitor and a second capacitor. One end of the energy storage capacitor is connected to the first power supply voltage, and the other end of the energy storage capacitor is grounded. The second capacitor is connected in parallel with the energy storage capacitor.

3. The microphone amplifier circuit according to claim 1, characterized in that, The operational amplifier circuit includes an operational amplifier, a fifth resistor, a sixth resistor, a seventh resistor, an eighth resistor, a third capacitor, and a fourth capacitor; The inverting input terminal of the operational amplifier is connected to the output terminal of the switching transistor amplifier circuit and the second signal output terminal of the microphone input interface module through the fifth resistor. The inverting input terminal of the operational amplifier is also connected to the output terminal of the operational amplifier through the sixth resistor and the third capacitor. The output terminal of the operational amplifier is connected to the subsequent power amplifier circuit. The non-inverting input terminal of the operational amplifier is connected to the second power supply voltage through the seventh resistor and grounded through the eighth resistor. The fourth capacitor is connected in parallel with the eighth resistor.

4. The microphone amplifier circuit according to claim 1, characterized in that, It also includes a microphone switching circuit and a main control chip, wherein the output of the microphone switching circuit is connected to the microphone input interface module and the switching tube amplifier circuit; The main control chip is connected to the input terminal of the microphone switching circuit and is used to control the power supply status of the microphone switching circuit.

5. The microphone amplifier circuit according to claim 4, characterized in that, The microphone switching circuit includes a switching circuit, a third transistor, a ninth resistor, a tenth resistor, an eleventh resistor, and a first diode; The emitter of the third transistor is connected to the first power supply voltage through the ninth resistor and is also connected to the negative terminal of the first diode and one end of the tenth resistor. The positive terminal of the first diode is grounded. The other end of the tenth resistor is connected to the base of the third transistor. The base of the third transistor is connected to the switching circuit. The collector of the third transistor is connected to the first signal output terminal of the microphone input interface module through the eleventh resistor. The main control chip is connected to the switching circuit and is used to control the on / off state of the third transistor through the switching circuit.

6. The microphone amplifier circuit according to claim 5, characterized in that, The switching circuit includes a fourth transistor, a fifth transistor, a twelfth resistor, and a thirteenth resistor; The collector of the fourth transistor is connected to the base of the third transistor, the emitter of the fourth transistor is grounded, the base of the fourth transistor is connected to the collector of the fifth transistor, the base of the fifth transistor is grounded through the twelfth resistor, and the emitter of the fifth transistor is connected to the main control chip through the thirteenth resistor.

7. The microphone amplifier circuit according to claim 1, characterized in that, The first transistor is an NPN transistor, and the second transistor is a PNP transistor.

8. The microphone amplifier circuit according to claim 6, characterized in that, The third and fifth transistors are both PNP transistors, and the fourth transistor is an NPN transistor.

9. An audio device, characterized in that, Includes the microphone amplifier circuit as described in any one of claims 1-8.

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