Microphone amplifier circuit, microphone circuit, and electronic device

Abstract

The embodiments of the present invention provide a microphone amplifier circuit, a microphone circuit, and an electronic device. The microphone amplifier circuit comprises: a voltage regulator having an output end, a first constant-current source having an input end connected to the output end of the voltage regulator, a first transistor, a second transistor, a first driving unit, and a second driving unit. A gate electrode of the first transistor serves as an input end of the microphone amplifier circuit, and a source electrode of the first transistor serves as an output end of the microphone amplifier circuit. A source electrode of the second transistor is connected to an output end of the first constant-current source, a gate electrode of the second transistor is connected to the source electrode of the first transistor, and a drain electrode of the second transistor is grounded. The first driving unit is used for increasing the power supply rejection ratio of the microphone amplifier circuit, and the second driving unit is used for improving the sound pressure overload point of the microphone amplifier circuit. The embodiments of the present invention at least facilitate an improvement to the electrical performance of microphone circuits.

Description

Microphone amplifier circuit, microphone circuit and electronic device Technical Field

[0001] The present invention relates to the technical field of microphones, and in particular to a microphone amplifier circuit, a microphone circuit and an electronic device. Background Art

[0002] With the development of mobile communication technology, mobile phones, smart speakers, laptops, etc. have become common electronic products in our lives. The microphone circuits installed in these electronic products usually include a microphone body and a microphone amplifier circuit. The microphone is used as a sound pickup unit to convert sound signals into electrical signals, and the microphone amplifier circuit is used to drive the signal output by the microphone to be output to subsequent devices. Technical issues

[0003] A microphone amplifier's signal-to-noise ratio (SNR), load drive capability, power supply rejection ratio (PSRR), and acoustic overload point (AOP)—among other performance parameters—significantly impacts the effectiveness and performance of subsequent devices. Therefore, these parameters are crucial indicators for evaluating product performance. However, the performance of current microphone amplifiers leaves much to be desired. Technical Solutions

[0004] Embodiments of the present invention provide a microphone amplifier circuit, a microphone circuit, and an electronic device, which are at least beneficial for improving the electrical performance of the microphone circuit.

[0005] One embodiment of the present invention provides a microphone amplifier circuit, comprising: a voltage regulator, a first constant current source, a first transistor, a first drive unit, and a second drive unit. The voltage regulator has an output terminal. The first constant current source has an input terminal connected to the output terminal of the voltage regulator. The gate of the first transistor serves as the input terminal of the amplifier circuit, and the source of the first transistor serves as the output terminal of the amplifier circuit. The source of the second transistor is connected to the output terminal of the first constant current source, the gate of the second transistor is connected to the source of the first transistor, and the drain of the second transistor is grounded. The first drive unit is configured to improve the power supply rejection ratio (PSR) of the amplifier circuit. A first terminal of the first drive unit is connected to the output terminal of the voltage regulator, a second terminal of the first drive unit is connected to the source of the second transistor, a third terminal of the first drive unit is connected to the source of the first transistor, a fourth terminal of the first drive unit is connected to the drain of the first transistor, and a fifth terminal of the first drive unit is grounded. The second drive unit is configured to increase the sound pressure overload point of the amplifier circuit. A first terminal of the second drive unit is connected to the power supply, a second terminal of the second drive unit is connected to the output terminal of the voltage regulator, a third terminal of the second drive unit is connected to the source of the first transistor, a fourth terminal of the second drive unit is connected to the drain of the first transistor, and a fifth terminal of the second drive unit is grounded.

[0006] In some embodiments, the amplifier circuit includes a bias resistor, a first end of the bias resistor is connected to the drain of the first transistor, and a second end of the bias resistor is grounded.

[0007] In some embodiments, the first transistor and the second transistor are both P-channel metal oxide semiconductor (PMOS) transistors.

[0008] In some embodiments, the voltage source is a low dropout linear regulator (LDO).

[0009] In some embodiments, the first drive unit includes: a bias current source, a third transistor, a fourth transistor, a fifth transistor, and a sixth transistor. The input end of the bias current source serves as the first end of the first drive unit. The gate of the third transistor serves as the fourth end of the first drive unit, the source of the third transistor serves as the fifth end of the first drive unit, and the drain of the third transistor serves as the third end of the first drive unit. The gate of the fourth transistor is connected to the gate of the third transistor, the source of the fourth transistor is connected to the source of the third transistor, and the drain of the fourth transistor is connected to the output end of the bias current source. The source of the fifth transistor is connected to the drain of the third transistor, the gate of the fifth transistor is connected to the drain of the fourth transistor. The gate of the sixth transistor serves as the second end of the first drive unit, the drain of the sixth transistor is connected to the output end of the voltage regulator, and the source of the sixth transistor is connected to the drain of the fifth transistor.

[0010] In some embodiments, the first driving unit further includes a capacitor, a first end of the capacitor is connected to the gate of the fifth transistor, and a second end of the capacitor is connected to the gate of the third transistor.

[0011] In some embodiments, the third transistor, the fourth transistor, the fifth transistor, and the sixth transistor are all N-channel metal oxide semiconductor (NMOS) transistors.

[0012] In some embodiments, the second drive unit includes: a second constant current source, a seventh transistor, an eighth transistor, a ninth transistor, a tenth transistor, and an eleventh transistor. The input terminal of the second constant current source serves as the second terminal of the second drive unit. The gate of the seventh transistor serves as the fourth terminal of the second drive unit, the source of the seventh transistor serves as the fifth terminal of the second drive unit, and the drain of the seventh transistor is connected to the output terminal of the second constant current source. The source of the eighth transistor is connected to the source of the seventh transistor, the drain of the eighth transistor is connected to the drain of the seventh transistor, and the gate of the eighth transistor is connected to the drain of the eighth transistor. The source of the ninth transistor is connected to the source of the seventh transistor, and the gate of the ninth transistor is connected to the gate of the eighth transistor. The source of the tenth transistor serves as the first terminal of the second drive unit, the drain of the tenth transistor serves as the third terminal of the second drive unit, and the gate of the tenth transistor is connected to the drain of the ninth transistor. The source of the eleventh transistor is connected to the source of the tenth transistor, the gate of the eleventh transistor is connected to the gate of the tenth transistor, and the drain of the eleventh transistor is connected to the gate of the eleventh transistor. The voltage output by the voltage regulator is lower than the power supply voltage.

[0013] In some embodiments, the seventh transistor, the eighth transistor, and the ninth transistor are all NMOS transistors, and the tenth transistor and the eleventh transistor are all PMOS transistors.

[0014] Another embodiment of the present invention provides a microphone circuit, comprising: a microphone and a microphone amplifier circuit as described in any one of the above embodiments. A first end of the microphone is connected to a microphone bias voltage, and a second end of the microphone is connected to an input end of the microphone amplifier circuit.

[0015] Another aspect of the present invention provides an electronic device, including: the microphone amplifier circuit as described in any one of the above embodiments, or including the microphone circuit as described in any one of the above embodiments.

[0016] In an embodiment of the present invention, when the signal received at the input of the microphone amplifier circuit is a small signal, the first drive unit is turned on and the second drive unit is turned off. Thus, the first drive unit, in the turned-on state, uses the relatively stable signal output by the voltage regulator as the power supply signal, which is beneficial for improving the power supply rejection ratio of the microphone amplifier circuit. When the signal received at the input of the microphone amplifier circuit is a large signal, the second drive unit is turned on. The turned-on second drive unit uses the power supply voltage as the power supply signal. The second drive unit is turned on, and the power supply serves as the power supply signal, which is beneficial for ensuring that the microphone amplifier circuit has a high sound pressure overload point. Furthermore, the microphone amplifier circuit provided in an embodiment of the present invention can output a load signal with a strong drive capability using a single-stage amplifier, without the need for an additional amplifier to increase the load signal drive capability. This not only ensures the output of a load signal with a large drive capability, but also ensures that the microphone amplifier circuit as a whole has a high signal-to-noise ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Embodiments of the invention are described by way of example and not limitation with reference to the accompanying drawings in which like references indicate similar elements.

[0018] FIG1 is a schematic diagram of a circuit structure of a microphone amplifier circuit provided by the related art;

[0019] FIG2 is a schematic diagram of the circuit structure of a microphone amplifier circuit provided by an embodiment of the present invention;

[0020] FIG3 is a schematic diagram of the circuit structure of another microphone amplifier circuit provided by an embodiment of the present invention;

[0021] FIG4 is a schematic diagram of the circuit structure of a microphone circuit provided by an embodiment of the present invention. Modes for Carrying Out the Invention

[0022] As can be seen from the background technology, the performance of microphone amplifier circuits, such as signal-to-noise ratio, load driving capability, and power supply rejection ratio, has a significant impact on the effect and performance of subsequent devices, and the performance of current microphone amplifier circuits needs to be improved.

[0023] Figure 1 is a schematic diagram of the circuit structure of a microphone amplifier circuit provided by the related art. Referring to Figure 1 , the input terminal IN0 of the amplifier circuit 10 is used to receive a signal from an external microphone, and the output terminal OUT0 of the amplifier circuit 10 is used to output the signal amplified by the amplifier circuit 10. Specifically, the amplifier circuit 10 includes a constant current source I0 and a transistor M0. The gate of the transistor M0 serves as the input terminal IN0 of the microphone amplifier circuit 10, the source of the transistor M0 serves as the output terminal OUT0 of the microphone amplifier circuit 10, and the drain of the transistor M0 is grounded GND. The input terminal of the constant current source I0 is connected to the power supply VDD, and the output terminal of the constant current source I0 is connected to the source of the transistor M0.

[0024] The output impedance of an ideal current source is infinite, and the output current of an ideal current source does not change with changes in the load. However, under normal circumstances, the constant current source I0 in the amplifier circuit 10 shown in Figure 1 is not an ideal current source, and the output impedance of the constant current source I0 is not large enough. As a result, the output signal Vout0 is easily affected by the fluctuation of the constant current source I0. Therefore, the power supply suppression of the amplifier circuit 10 is relatively low. In addition, in the amplifier circuit 10, the main part that performs the amplification function is the source follower composed of the transistor M0. The voltage of the input signal Vin0 is the same as the voltage of the output signal Vout0, and the gain of the amplifier is 1. Therefore, the output drive capability of the amplifier circuit 10 is low. If an additional amplifier is added, for example, a second buffer amplifier is added to improve the output drive capability of the amplifier circuit 10, the overall signal-to-noise ratio of the amplifier circuit 10 will be low.

[0025] To address the aforementioned issues, embodiments of the present invention provide a microphone amplifier circuit that improves the amplifier circuit's power supply rejection ratio (PSRR) and ensures a high sound pressure overload point. Furthermore, this circuit not only outputs a load signal with a high drive capability, but also ensures a high signal-to-noise ratio for the entire amplifier circuit.

[0026] The following describes various embodiments of the present invention in detail with reference to the accompanying drawings. However, those skilled in the art will appreciate that many technical details are provided in the various embodiments of the present invention to facilitate a better understanding of the embodiments of the present invention. However, even without these technical details and the various variations and modifications based on the following embodiments, the technical solutions claimed in the embodiments of the present invention can still be implemented.

[0027] FIG2 is a schematic diagram of the circuit structure of a microphone amplifier circuit provided by an embodiment of the present invention.

[0028] 2 , the amplifier circuit 200 is configured to receive a sound pressure signal output by an external microphone through an input terminal IN1 , and amplify the sound pressure signal and output it through an output terminal OUT1 .

[0029] The amplifier circuit 200 includes a voltage regulator LDO and a first constant current source I1. An input terminal of the first constant current source I1 is connected to an output terminal of the voltage regulator LDO.

[0030] In some embodiments, the voltage regulator LDO is a low dropout linear regulator.

[0031] A low-dropout linear regulator (LDO) is used to stably output a fixed voltage based on the input voltage. It automatically adjusts the output voltage when the power supply VDD fluctuates or the load changes, maintaining a constant output voltage. This LDO minimizes the impact of power supply fluctuations on the load signal output by amplifier circuit 200, improving the power supply rejection ratio (PSR) of amplifier circuit 200 and, consequently, the electrical performance of amplifier circuit 200.

[0032] 2 , the amplifier circuit 200 further includes a first transistor M1 and a second transistor M2. The gate of the first transistor M1 serves as the input terminal IN1 of the amplifier circuit 200, the source of the first transistor M1 serves as the output terminal OUT1 of the amplifier circuit 200, and the drain of the first transistor M1 is connected to ground GND. The source of the second transistor M2 is connected to the output terminal of the first constant current source I1, the gate of the second transistor M2 is connected to the source of the first transistor M1, and the drain of the second transistor M2 is connected to ground GND.

[0033] The amplifier circuit 200 provided in the embodiment of the present invention can output a load signal with a strong driving capability by using a single-stage amplifier, and does not require the addition of an additional amplifier to enhance the driving capability of the load signal. This is not only beneficial for outputting a load signal with a large driving capability, but also ensures that the amplifier circuit 200 as a whole has a high signal-to-noise ratio.

[0034] In some embodiments, the first transistor M1 and the second transistor M2 are both PMOS transistors.

[0035] In some embodiments, the amplifier circuit 200 includes a bias resistor R1. In this case, the drain of the first transistor M1 is grounded through the bias resistor R1. Specifically, a first end of the bias resistor R1 is connected to the drain of the first transistor M1, and a second end of the bias resistor R1 is grounded.

[0036] The primary amplification component of amplifier circuit 200 is a source-follower circuit formed by first transistor M1. Bias resistor R1 provides a current bias, thereby providing a sink current to ground GND for first transistor M1. A second transistor M2 and a first constant current source I1 form a source-follower circuit, acting as a level shifter to increase the voltage at the source of first transistor M1. This improves the output drive capability of amplifier circuit 200.

[0037] Continuing with reference to FIG2 , the amplifier circuit 200 further includes a first drive unit 210 and a second drive unit 220. The first drive unit 210 is configured to improve the power supply rejection ratio (PSR) of the amplifier circuit 200. The second drive unit 220 is configured to increase the sound pressure overload point (SOP) of the amplifier circuit 200. A first terminal A1 of the first drive unit 210 is connected to the output terminal of the voltage regulator LDO, a second terminal A2 of the first drive unit 210 is connected to the output terminal of the first constant current source I1, a third terminal A3 of the first drive unit 210 is connected to the source of the first transistor M1, a fourth terminal A4 of the first drive unit 210 is connected to the drain of the first transistor M1, and a fifth terminal A5 of the first drive unit 210 is connected to ground GND. A first terminal B1 of the second driving unit 220 is connected to the power supply VDD, a second terminal B2 of the second driving unit 220 is connected to the output terminal of the voltage regulator LDO, a third terminal B3 of the second driving unit 220 is connected to the source of the first transistor M1, a fourth terminal B4 of the second driving unit 220 is connected to the drain of the first transistor M1, and a fifth terminal B5 of the second driving unit 220 is connected to the ground GND.

[0038] When the external sound pressure received by the external microphone is small, the amplitude of the sound pressure signal output by the microphone is small, that is, the signal received by the input terminal IN1 of the amplifier circuit 200 is a small signal. If the signal received by the input terminal IN1 of the amplifier circuit 200 is a small signal, the fluctuation of the power supply signal is more likely to affect the load signal output by the amplifier circuit 200, that is, the harmonics generated by the fluctuation of the power supply signal in the load signal have a greater impact on the load signal. In an embodiment of the present invention, when the signal received by the input terminal IN1 of the amplifier circuit 200 is a small signal, the first drive unit 210 is turned on and the second drive unit 220 is turned off. In this way, the first drive unit 210 in the turned-on state uses the relatively stable signal output by the voltage regulator LDO as the power supply signal. The relatively stable power supply signal makes the load signal output by the amplifier circuit 200 less affected by the fluctuation of the power supply signal, which is beneficial to improving the power supply rejection ratio of the amplifier circuit 200, thereby improving the electrical performance of the amplifier circuit 200.

[0039] When the external sound pressure received by the external microphone is high, the amplitude of the sound pressure signal output by the microphone is large, that is, the signal received by the input terminal IN1 of the amplifier circuit 200 is a large signal. When the signal received by the input terminal IN1 of the amplifier circuit 200 is a large signal, the second drive unit 220 is turned on. Because the voltage output by the voltage regulator LDO is lower than the power supply voltage VDD, the power supply voltage VDD serves as the power signal, preventing the load signal from being limited by the voltage regulator LDO, which helps ensure that the microphone circuit as a whole has a high sound pressure overload point.

[0040] FIG3 is a schematic diagram of the circuit structure of another microphone amplifier circuit provided by an embodiment of the present invention. Amplifier circuit 300 in FIG3 has a similar structure to amplifier circuit 200 shown in FIG2 , except for first drive unit 310 and second drive unit 320. Components in FIG3 similar to those in FIG2 are not described again here.

[0041] Continuing with FIG3 , the first drive unit 310 includes a bias current source IB, a third transistor M3, a fourth transistor M4, a fifth transistor M5, and a sixth transistor M6. The input terminal of the bias current source IB is connected to the output terminal of the voltage regulator LDO and serves as the first terminal A1 of the first drive unit 310. The gate of the third transistor M3 is connected to the drain of the first transistor M1 and serves as the fourth terminal A4 of the first drive unit 310. The source of the third transistor M3 is grounded and serves as the fifth terminal A5 of the first drive unit 310. The drain of the third transistor M3 is connected to the source of the first transistor M1 and serves as the third terminal A3 of the first drive unit 310. The gate of the fourth transistor M4 is connected to the gate of the third transistor M3, the source of the fourth transistor M4 is connected to the source of the third transistor M3, and the drain of the fourth transistor M4 is connected to the output terminal of the bias current source IB. The source of the fifth transistor M5 is connected to the drain of the third transistor M3, and the gate of the fifth transistor M5 is connected to the drain of the fourth transistor M4. The gate of the sixth transistor M6 is connected to the source of the second transistor M2 and serves as the second terminal A2 of the first driving unit 110. The drain of the sixth transistor M6 is connected to the output end of the voltage regulator LDO. The source of the sixth transistor M6 is connected to the drain of the fifth transistor M5.

[0042] The fourth transistor M4, bias current source IB, and bias resistor R1 are used to provide a current bias, providing a sink current to ground GND for the first transistor M1. The second transistor M2 and the first constant current source I1 are used to provide a voltage bias for the gate of the sixth transistor M6. The fifth transistor M5 is used to provide current from the amplifier circuit 300 to the external circuit, and the third transistor M3 is used to provide current from the external circuit to the microphone amplifier circuit 300, thereby enabling the amplifier circuit 300 to have push-pull current driving capabilities.

[0043] When the voltage value of the signal received by the input terminal IN1 of the amplifier circuit 300 increases, the gate voltage of the first transistor M1, the gate voltage of the second transistor M2, and the gate voltage of the sixth transistor M6 all increase, and the gate voltage of the third transistor M3 and the gate voltage of the fourth transistor M4 decrease. The channel current of the fifth transistor M5 increases, and the channel current of the third transistor M3 and the channel current of the fourth transistor M4 both decrease. Therefore, the current flowing out of the source of the fifth transistor M5, after being divided by the first transistor M1 and the third transistor M3, flows to the output terminal OUT1.

[0044] When the voltage value of the signal received by the input terminal IN1 of the amplifier circuit 300 decreases, the gate voltage of the first transistor M1, the gate voltage of the second transistor M2, and the gate voltage of the sixth transistor M6 all decrease, the gate voltage of the third transistor M3 and the gate voltage of the fourth transistor M4 all increase, the channel current of the fifth transistor M5 decreases, and the channel current of the third transistor M3 and the channel current of the fourth transistor M4 both increase. Therefore, after receiving the current flowing from the fifth transistor M5 and the first transistor M1, the third transistor M3 forms a current sink, and an external circuit or load can flow a large current into the third transistor M3 through the output terminal OUT1 of the amplifier circuit 300.

[0045] In summary, the amplifier circuit 300 can both output a large current from the output terminal OUT1 to the external circuit and allow a large current to flow into the amplifier circuit 300 from the output terminal OUT1 .

[0046] In some embodiments, the third transistor M3 , the fourth transistor M4 , the fifth transistor M5 , and the sixth transistor M6 are all NMOS transistors.

[0047] In some embodiments, the first driving unit 310 further includes a capacitor C, a first end of the capacitor C is connected to the gate of the fifth transistor, and a second end of the capacitor C is connected to the gate of the third transistor M3.

[0048] In some embodiments, referring to FIG3 , the second drive unit 320 includes: a second constant current source I2, a seventh transistor M7, an eighth transistor M8, a ninth transistor M9, a tenth transistor M10, and an eleventh transistor M11. The input terminal of the second constant current source I2 serves as the second terminal B2 of the second drive unit 320. The gate of the seventh transistor M7 serves as the fourth terminal B4 of the second drive unit 320, the source of the seventh transistor M7 serves as the fifth terminal B5 of the second drive unit 320, and the drain of the seventh transistor M7 is connected to the output terminal of the second constant current source I2. The source of the eighth transistor M8 is connected to the source of the seventh transistor M7, the drain of the eighth transistor M8 is connected to the drain of the seventh transistor M7, and the gate of the eighth transistor M8 is connected to the drain of the eighth transistor M8. The source of the ninth transistor M9 is connected to the source of the seventh transistor M7, and the gate of the ninth transistor M9 is connected to the gate of the eighth transistor M8. The source of the tenth transistor M10 is connected to the power supply VDD and serves as the first terminal B1 of the second driving unit 320. The drain of the tenth transistor M10 is connected to the source of the first transistor and serves as the first terminal B3 of the second driving unit 320. The gate of the tenth transistor M10 is connected to the drain of the ninth transistor M9. The source of the eleventh transistor M11 is connected to the source of the tenth transistor M10, the gate of the eleventh transistor M11 is connected to the gate of the tenth transistor M10, and the drain of the eleventh transistor M11 is connected to the gate of the eleventh transistor M11.

[0049] In the second driving unit 320 , the eighth transistor M8 , the ninth transistor M9 , the tenth transistor M10 and the eleventh transistor M11 form a current mirror for amplifying a net current obtained by subtracting the current flowing through the seventh transistor M7 from the current output from the second constant current source I2 .

[0050] The first drive unit 310 is always in the on state, and the power supply voltage is provided by the voltage regulator LDO. The voltage regulator LDO is conducive to providing a high power supply rejection ratio. However, because the voltage output by the voltage regulator LDO is lower than the power supply voltage VDD, if the voltage value of the signal received by the input terminal IN1 of the amplifier circuit 300 is relatively high, the voltage regulator LDO is still used to provide the power signal. The internal signal of the first drive unit 310 will be clamped by the voltage output by the voltage regulator LDO and cannot reach the power supply voltage VDD, resulting in a low sound pressure overload point. To solve the above problem, the embodiment of the present invention provides a second drive unit 320. Because the impact of the power supply rejection ratio on the load signal is negligible when the voltage value of the signal received by the input terminal IN1 of the amplifier circuit 300 is relatively high, the second drive unit 320 is turned on, raising the upper limit of the load signal voltage to the power supply voltage VDD, so that the voltage of the load signal is not clamped by the output voltage of the voltage regulator LDO, which is conducive to ensuring that the overall system has a high sound pressure overload point.

[0051] When the voltage value of the signal received by the input terminal IN1 of the amplifier circuit 300 increases, the gate voltage of the seventh transistor M7 decreases, and the channel current of the seventh transistor M7 decreases. When the voltage value of the signal received by the input terminal IN1 of the amplifier circuit 300 further increases, the gate voltage of the seventh transistor M7 further decreases, and the channel current of the seventh transistor M7 further decreases. When the channel current of the seventh transistor M7 is less than the output current of the current source I2, the net current obtained by subtracting the channel current of the seventh transistor M7 from the output current of the current source I2 is amplified by the current mirror and outputted through M10. At this time, the second drive unit 320 is in the open state.

[0052] It should be noted that due to the limited output impedance of the current mirror formed by the eleventh transistor M11 and the tenth transistor M10, the power supply rejection ratio (PSRR) of the second driving unit 320 when in the on state is low. Therefore, when the voltage value of the signal received by the input terminal IN1 of the amplifier circuit 300 is sufficiently large, and the output current of the second constant current source I2 is greater than the channel current of the seventh transistor M7, the second driving unit 320 is turned on. In this way, when the voltage value of the signal received by the input terminal IN1 of the amplifier circuit 300 is relatively small, the second driving unit 320 is turned on to avoid reducing the PSRR.

[0053] Furthermore, it should be noted that the current provided by the second constant current source I2 to the drain of the seventh transistor M7 flows through the seventh transistor M7, forming a current flowing out of the source of the seventh transistor M7. When the voltage value of the signal received by the input terminal IN1 of the amplifier circuit 300 increases, the gate voltage of the seventh transistor M7 decreases. When the channel current of the seventh transistor M7 is less than the output current of the second constant current source I2, the current flowing out of the second constant current source I2 is shunted by the seventh transistor M7, amplified by the current mirror, and then flows out of the output terminal OUT1 of the amplifier circuit 300 through the tenth transistor M10.

[0054] In some embodiments, the seventh transistor M7 , the eighth transistor M8 , and the ninth transistor M9 are all NMOS transistors, and the tenth transistor M10 and the eleventh transistor M11 are all PMOS transistors.

[0055] The amplifier circuit 300 provided in the above embodiment uses a single-stage amplifier to output a load signal with a strong driving capability, which not only ensures the output of a load signal with a large driving capability, but also ensures that the amplifier circuit 300 as a whole has a high signal-to-noise ratio. When the signal received by the input terminal IN1 of the amplifier circuit 300 is a small signal, the first drive unit 310 is turned on and the second drive unit 320 is turned off. The first drive unit 310 in the turned-on state uses the relatively stable signal output by the voltage regulator LDO as the power supply signal, which is beneficial for improving the power supply rejection ratio of the amplifier circuit 300. When the signal received by the input terminal IN1 of the amplifier circuit 300 is a large signal, so that the output current of the second constant current source I2 is greater than the channel current of the seventh transistor IM7, the second drive unit 320 is turned on and uses the power supply voltage VDD as the power supply signal, which is beneficial for ensuring that the amplifier circuit 300 still has a high sound pressure overload point. It should be noted that the second driver 320 is only turned on when the signal received by the input terminal IN1 is a large positive signal, so that the output current of the second constant current source I2 is greater than the channel current of the seventh transistor IM7. If the signal received by input terminal IN1 is large but negative, the channel current of seventh transistor IM7 is greater than the output current of second constant current source I2, and second driver 320 remains in the off state. Here, positive indicates that the signal received by input terminal IN1 is higher than the DC bias, and negative indicates that the signal received by input terminal IN1 is lower than the DC bias. Small signal or large signal refers to the signal amplitude.

[0056] FIG4 is a schematic diagram of the circuit structure of a microphone circuit provided by an embodiment of the present invention.

[0057] 4 , another embodiment of the present invention further provides a microphone circuit, comprising: a microphone Mic and a microphone amplifier circuit 300 as in any one of the above embodiments, wherein a first end of the microphone Mic is connected to a microphone bias voltage Vcp, and a second end of the microphone is connected to an input end IN1 of the microphone amplifier circuit 300.

[0058] Another aspect of the present invention provides an electronic device, comprising: the microphone amplifier circuit as described in any one of the above embodiments, or comprising the microphone circuit as described in any one of the above embodiments.

[0059] It will be understood that although the terms first, second, etc. are used in some cases herein to describe various components, these components should not be limited by these terms. These terms are only used to distinguish one component from another. For example, a first transistor can be referred to as a second transistor, and similarly, a second transistor can be referred to as a first transistor without departing from the scope of the various embodiments described. The first constant current source and the second constant current source are both constant current sources, but their conditions are not the same unless explicitly stated.

[0060] Throughout this specification, when a component is referred to as "including" another component, unless otherwise specified, this does not exclude other components, and other components may also be included. In addition, when a component such as a transistor is referred to as being "connected" to another component, it may be "directly connected" to the other component or another component may be present therebetween. Furthermore, when a component is "directly connected" to another component, this means that no other components are present therebetween.

[0061] The terms used herein in the description of the various described embodiments are intended only to describe the particular embodiments and are not intended to be limiting. As used in the description of the various described embodiments and in the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that the term "and / or," as used herein, refers to and encompasses any and all possible combinations of one or more of the associated listed items. It should be further understood that the terms "includes," "including," "comprises," and / or "comprising" as used herein specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0062] Those skilled in the art will appreciate that the above-described embodiments are specific examples of the present invention, and that in actual applications, various changes in form and detail may be made thereto without departing from the spirit and scope of the present invention. Any person skilled in the art may make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope defined in the claims.

Claims

1. A microphone amplification circuit, characterized in that, Comprising: A voltage regulator with an output terminal; A first constant current source with an input terminal connected to the output terminal of the voltage regulator; A first transistor having a gate as the input terminal of the microphone amplification circuit, a source as the output terminal of the microphone amplification circuit, and a drain; A second transistor having a source connected to the output terminal of the first constant current source, a gate connected to the source of the first transistor, and a drain grounded; A first driving unit for improving the power supply rejection ratio of the microphone amplification circuit, having a first terminal connected to the output terminal of the voltage regulator, a second terminal connected to the source of the second transistor, a third terminal connected to the source of the first transistor, a fourth terminal connected to the drain of the first transistor, and a fifth terminal grounded; And A second driving unit for improving the sound pressure overload point of the microphone amplification circuit, having a first terminal connected to a power supply, a second terminal connected to the output terminal of the voltage regulator, a third terminal connected to the source of the first transistor, a fourth terminal connected to the drain of the first transistor, and a fifth terminal grounded; Wherein, the voltage output by the voltage regulator is lower than the voltage of the power supply.

2. The microphone amplifier circuit according to claim 1, wherein The microphone amplification circuit further includes a bias resistor; the drain of the first transistor is grounded through the bias resistor.

3. The microphone amplification circuit according to claim 1, wherein Both the first transistor and the second transistor are P-channel metal oxide semiconductor transistors.

4. The microphone amplification circuit according to claim 1, characterized in that, The voltage regulator is a low dropout linear regulator.

5. The microphone amplification circuit according to claim 1, characterized in that, The first driving unit includes: A bias current source having an input terminal as the first terminal of the first driving unit; A third transistor having a gate as the fourth terminal of the first driving unit, a source as the fifth terminal of the first driving unit, and a drain as the third terminal of the first driving unit; A fourth transistor having a gate connected to the gate of the third transistor, a source connected to the source of the third transistor, and a drain connected to the output terminal of the bias current source; A fifth transistor having a source connected to the drain of the third transistor, a gate connected to the drain of the fourth transistor, and a drain; and A sixth transistor having a gate as the second terminal of the first driving unit, a drain connected to the input terminal of the bias current source, and a source connected to the drain of the fifth transistor.

6. The microphone amplification circuit according to claim 5, wherein The first driving unit further includes a capacitor having a first terminal connected to the gate of the fifth transistor and a second terminal connected to the gate of the third transistor.

7. The microphone amplification circuit according to claim 5, characterized in that, The third transistor, the fourth transistor, the fifth transistor, and the sixth transistor are all N-channel metal oxide semiconductor transistors.

8. The microphone amplification circuit according to claim 1, wherein The second driving unit includes: A second constant current source having an input terminal as the second terminal of the second driving unit and an output terminal; A seventh transistor having a gate as the fourth terminal of the second driving unit, a source as the fifth terminal of the second driving unit, and a drain connected to the output terminal of the second constant current source; The eighth transistor has a source connected to the source of the seventh transistor, a drain connected to the drain of the seventh transistor, and a gate connected to the drain of the eighth transistor; The ninth transistor has a source connected to the source of the seventh transistor, a gate connected to the gate of the eighth transistor, and a drain; The tenth transistor has a source as the first end of the second driving unit, a drain as the third end of the second driving unit, and a gate connected to the drain of the ninth transistor; The eleventh transistor has a source connected to the source of the tenth transistor, a gate connected to the gate of the tenth transistor, and a drain connected to the gate of the eleventh transistor.

9. The microphone amplification circuit according to claim 8, wherein The seventh transistor, the eighth transistor, and the ninth transistor are all N-channel metal oxide semiconductor transistors, and the tenth transistor and the eleventh transistor are both P-channel metal oxide semiconductor transistors.

10. A microphone circuit, characterized in that, Comprising: The microphone amplification circuit according to any one of claims 1 to 9, and A microphone having a first end connected to a microphone bias voltage and a second end connected to the input end of the microphone amplification circuit.

11. An electronic device, characterized in that, Comprising: The microphone amplification circuit according to any one of claims 1 to 9, or comprising the microphone circuit according to claim 10.

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