Single-ended to differential microphone circuit and electronic device

Abstract

This invention provides a single-ended to differential microphone circuit and electronic device, comprising: an amplifier, a microphone connected to the positive input terminal of the amplifier, and a coupling capacitor C connected to the negative input terminal of the amplifier. AC The first feedback capacitor C connected to the negative output terminal of the amplifier FB1 , and the first feedback capacitor C FB1 The first feedback resistor R in parallel FB1 The second feedback capacitor C is connected to the positive output terminal of the amplifier. FB2 and the second feedback capacitor C FB1 The second feedback resistor R in parallel FB2 The microphone and the input terminal of the coupling capacitor are connected to a bias resistor R. B The bias resistor R B This allows AC signals to be input simultaneously to both the positive and negative input terminals of the amplifier. The circuit of this invention can employ a microphone structure with a smaller capacitor, while also achieving a better system signal-to-noise ratio.

Description

[Technical Field]

[0001] This invention relates to the field of electronic technology, and in particular to a single-ended to differential microphone circuit and electronic device. [Background Technology]

[0002] Microphone circuits generally have two output modes: single-ended and differential. Single-ended output tends to have higher noise levels, while differential output can filter out noise more effectively.

[0003] Traditional single-ended to differential circuits, such as Figure 1 As shown, when the closed-loop gain is set to 1, the circuit requires C... DMY =C MEMS =C FB However, with the development of microphone technology, the equivalent capacitance C of the microphone... MEMS The smaller the value, the smaller the feedback capacitor C becomes in order to maintain a closed-loop gain of 1. FB The size also needs to be reduced accordingly. However, the signal-to-noise ratio is important for the feedback capacitor C. FB The change sensitivity is high, if the feedback capacitor C... FB A smaller value will result in a worse signal-to-noise ratio at the output. Additionally, the high-voltage terminal V... HCM It is the location for communication; the communication signal is at V. INP Terminal input. When the amplitude of the input signal is large, the input terminal V... INP and V INN common-mode voltage V IN，CM There will be a large amplitude. V IN，CM The amplitude is V OUTP The amplitude is half of the input common-mode voltage. Therefore, the amplifier Amp must be an amplifier with a large input common-mode voltage range. [Summary of the Invention]

[0004] The purpose of this invention is to provide a single-ended to differential microphone circuit and electronic device to solve the above-mentioned technical problems.

[0005] To achieve the above objectives, in a first aspect, embodiments of the present invention provide a single-ended to differential microphone circuit, comprising: an amplifier, a microphone connected to the positive input terminal of the amplifier, and a coupling capacitor C connected to the negative input terminal of the amplifier. AC The first feedback capacitor C connected to the negative output terminal of the amplifier FB1 , and the first feedback capacitor C FB1 The first feedback resistor R in parallel FB1 The second feedback capacitor C is connected to the positive output terminal of the amplifier. FB2 and the second feedback capacitor C FB1 The second feedback resistor R in parallel FB2 ;

[0006] The microphone and the input terminal of the coupling capacitor are connected to a bias resistor R. B The bias resistor R B This allows AC signals to be input simultaneously at both the positive and negative input terminals of the amplifier.

[0007] Preferably, the coupling capacitor C AC The capacitance is at least four times that of the microphone.

[0008] Preferably, the amplifier includes: a P-type input transistor M1, a P-type input transistor M2, an N-type input transistor M3, an N-type input transistor M4, and an output load;

[0009] The sources of the P-type input transistors M1 and M2 are connected to the bias current IB. The gates of the P-type input transistors M1 and M2 are connected to the positive and negative input terminals of the amplifier, respectively. The drains of the N-type input transistors M3 and M4 are connected to the drains of the P-type input transistors M1 and M2, respectively. The gates of the N-type input transistors M3 and M4 are connected to the positive and negative input terminals of the amplifier, respectively. The sources of the N-type input transistors M3 and M4 are connected to the output load.

[0010] Preferably, the output load is a load transistor M5 and a load transistor M6, the gates of the load transistors M5 and M6 are respectively connected to the drains of the P-type input transistors M1 and M2, and the drains of the load transistors M5 and M6 are respectively connected to the sources of the N-type input transistors M3 and M4.

[0011] The transconductances of the P-type input transistor M1, P-type input transistor M2, N-type input transistor M3, and N-type input transistor M4 are added together and then converted into voltage by the load transistors M5 and M6, which is output at the output terminal.

[0012] Preferably, the equivalent capacitance of the microphone is less than 2pF.

[0013] Secondly, the present invention provides an electronic device including a single-ended to differential microphone circuit, the single-ended to differential microphone circuit comprising: an amplifier, a microphone connected to the positive input terminal of the amplifier, and a coupling capacitor C connected to the negative input terminal of the amplifier. AC The first feedback capacitor C connected to the negative output terminal of the amplifier FB1 , and the first feedback capacitor C FB1 The first feedback resistor R in parallel FB1 The second feedback capacitor C is connected to the positive output terminal of the amplifier.FB2 and the second feedback capacitor C FB1 The second feedback resistor R in parallel FB2 ;

[0014] The microphone and the input terminal of the coupling capacitor are connected to a bias resistor R. B The bias resistor R B This allows AC signals to be input simultaneously at both the positive and negative input terminals of the amplifier.

[0015] Preferably, the coupling capacitor C AC The capacitance is at least four times that of the microphone.

[0016] Preferably, the amplifier includes: a P-type input transistor M1, a P-type input transistor M2, an N-type input transistor M3, an N-type input transistor M4, and an output load;

[0017] The sources of the P-type input transistors M1 and M2 are connected to the bias current IB. The gates of the P-type input transistors M1 and M2 are connected to the positive and negative input terminals of the amplifier, respectively. The drains of the N-type input transistors M3 and M4 are connected to the drains of the P-type input transistors M1 and M2, respectively. The gates of the N-type input transistors M3 and M4 are connected to the positive and negative input terminals of the amplifier, respectively. The sources of the N-type input transistors M3 and M4 are connected to the output load.

[0018] Preferably, the output load is a load transistor M5 and a load transistor M6, the gates of the load transistors M5 and M6 are respectively connected to the drains of the P-type input transistors M1 and M2, and the drains of the load transistors M5 and M6 are respectively connected to the sources of the N-type input transistors M3 and M4.

[0019] The transconductances of the P-type input transistor M1, P-type input transistor M2, N-type input transistor M3, and N-type input transistor M4 are added together and then converted into voltage by the load transistors M5 and M6, which is output at the output terminal.

[0020] Preferably, the equivalent capacitance of the microphone is less than 2pF.

[0021] Compared with related technologies, the present invention maintains the microphone C by introducing a bias resistor and combining it with a feedback resistor. MEMS The two ends are high impedance, and the coupling capacitor C AC Both ends of the amplifier are also high impedance, so the AC signal can pass through the amplifier's V... INP and VINN Input at both ends. Coupling capacitor C AC After AC coupling of the input signal, it enters V INN Microphone C MEMS It will find an internal equilibrium point. When the closed-loop gain is 1, C FB =2C MEMS Therefore, the feedback capacitor C FB It can be compared to C MEMS Doubling the size allows for greater filtering of the amplifier's own noise, thus improving the overall signal-to-noise ratio of the system.

[0022] In one embodiment, because the AC signal can simultaneously originate from the positive and negative input terminals V INP V INN Input, common-mode voltage V at the input terminal IN,CM The amplitude will be significantly reduced, ideally even to zero. Therefore, a current-reuse amplifier (CR-Amp) with a relatively small input common-mode voltage range can be used.

[0023] In one embodiment, the input terminal of the CR-Amp can simultaneously obtain the transconductance of both P-type and N-type inputs under the same current bias, thereby increasing the input transconductance by approximately double, thus reducing the amplifier noise and improving the signal-to-noise ratio of the entire system. [Attached Image Description]

[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0025] Figure 1 This is a circuit schematic diagram of an existing single-ended to differential microphone circuit;

[0026] Figure 2 This is a circuit diagram of a single-ended to differential microphone circuit in an embodiment of the present invention;

[0027] Figure 3 This is a circuit diagram of the amplifier in an embodiment of the present invention.

Detailed Implementation Methods

[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] Please see Figure 1 This invention provides a single-ended to differential microphone circuit, comprising: an amplifier CR-Amp, and a circuit connected to the positive input terminal V of the amplifier CR-Amp. INP microphone C MEMS , connected to the negative input terminal V of the amplifier CR-Amp INN Coupling capacitor C AC Connect the negative output terminal V of the amplifier. OUTN The first feedback capacitor C FB1 , and the first feedback capacitor C FB1 The first feedback resistor R in parallel FB1 Connect the positive output terminal V of the amplifier. OUTP Second feedback capacitor C FB2 and the second feedback capacitor C FB1 The second feedback resistor R in parallel FB2 The microphone C MEMS and the coupling capacitor C AC The input terminal is connected to a bias resistor R. B The bias resistor R B This allows AC signals to be input simultaneously at both the positive and negative input terminals of the amplifier.

[0031] In this embodiment, the coupling capacitor C AC The capacitor size is at least four times that of the microphone, used for R... B To avoid connecting a high-voltage DC to the negative input terminal of the amplifier, which could affect the entire circuit. HCM It is a high voltage bias voltage of 13.8V.

[0032] In this embodiment, the amplifier includes: a P-type input transistor M1, a P-type input transistor M2, an N-type input transistor M3, an N-type input transistor M4, and an output load; the sources of the P-type input transistors M1 and M2 are connected to the bias current IB, the gates of the P-type input transistors M1 and M2 are respectively connected to the positive input terminal and the negative input terminal of the amplifier, the drains of the N-type input transistors M3 and M4 are respectively connected to the drains of the P-type input transistors M1 and M2, the gates of the N-type input transistors M3 and M4 are respectively connected to the positive input terminal and the negative input terminal of the amplifier, and the sources of the N-type input transistors M3 and M4 are respectively connected to the output load.

[0033] In this embodiment, the output load is load transistor M5 and load transistor M6. The gates of load transistors M5 and M6 are respectively connected to the drains of P-type input transistors M1 and M2, and the drains of load transistors M5 and M6 are respectively connected to the sources of N-type input transistors M3 and M4. The transconductance of P-type input transistors M1, M2, M3, and M4 is added together and then converted into voltage by load transistors M5 and M6 and output at the output terminal.

[0034] In this embodiment, the amplifier doubles its transconductance and reduces noise under the same bias current. Although the input common-mode voltage range of the amplifier in this embodiment is relatively small, because in this embodiment, AC signals can simultaneously enter from the positive and negative input terminals V... INP V INN Input, common-mode voltage V at the input terminal IN,CM The amplitude will be significantly reduced, ideally to zero. Therefore, the entire circuit can adopt the amplifier structure in this embodiment.

[0035] In this embodiment, because it has a smaller requirement for feedback capacitance, the equivalent capacitance C of the microphone is... MEMS Less than 2pF.

[0036] Compared with related technologies, the present invention maintains the microphone C by introducing a bias resistor and combining it with a feedback resistor. MEMS The two ends are high impedance, and the coupling capacitor C AC Both ends of the amplifier are also high impedance, so the AC signal can pass through the amplifier's V... INP and V INN Input at both ends. Coupling capacitor C AC After AC coupling of the input signal, it enters V INN Microphone C MEMSIt will find an internal equilibrium point. When the closed-loop gain is 1, C FB =2C MEMS Therefore, the feedback capacitor C FB It can be relative to the microphone capacitance C MEMS Doubling the size allows for greater filtering of the amplifier's own noise, thus improving the overall signal-to-noise ratio of the system.

[0037] In one embodiment, because the AC signal can simultaneously originate from the positive and negative input terminals V INP V INN Input, common-mode voltage V at the input terminal IN,CM The amplitude will be significantly reduced, ideally even to zero. Therefore, a current-reuse amplifier (CR-Amp) with a relatively small input common-mode voltage range can be used.

[0038] In one embodiment, the input terminal of the CR-Amp can simultaneously obtain the transconductance of both P-type and N-type inputs under the same current bias, thereby increasing the input transconductance by approximately double, thus reducing the amplifier noise and improving the signal-to-noise ratio of the entire system.

[0039] Example 2

[0040] This invention provides an electronic device, which can be a mobile phone, music player, computer, or other smart device. This electronic device includes a single-ended to differential microphone circuit, comprising: an amplifier CR-Amp, and a microphone connected to the positive input terminal V of the amplifier CR-Amp. INP microphone C MEMS , connected to the negative input terminal V of the amplifier CR-Amp INN Coupling capacitor C AC Connect the negative output terminal V of the amplifier. OUTN The first feedback capacitor C FB1 , and the first feedback capacitor C FB1 The first feedback resistor R in parallel FB1 Connect the positive output terminal V of the amplifier. OUTP Second feedback capacitor C FB2 and the second feedback capacitor C FB1 The second feedback resistor R in parallel FB2 The microphone C MEMS and the coupling capacitor C AC The input terminal is connected to a bias resistor R. B The bias resistor R B This allows AC signals to be input simultaneously at both the positive and negative input terminals of the amplifier.

[0041] In this embodiment, the coupling capacitor CAC The capacitor size is at least four times that of the microphone, used for R... B To avoid connecting a high-voltage DC to the negative input terminal of the amplifier, which could affect the entire circuit. HCM It is a high voltage bias voltage of 13.8V.

[0042] In this embodiment, the amplifier includes: a P-type input transistor M1, a P-type input transistor M2, an N-type input transistor M3, an N-type input transistor M4, and an output load; the sources of the P-type input transistors M1 and M2 are connected to a bias current IB, the gates of the P-type input transistors M1 and M2 are respectively connected to the positive input terminal and the negative input terminal of the amplifier, the drains of the N-type input transistors M3 and M4 are respectively connected to the drains of the P-type input transistors M1 and M2, the gates of the N-type input transistors M3 and M4 are respectively connected to the positive input terminal and the negative input terminal of the amplifier, and the sources of the N-type input transistors M3 and M4 are respectively connected to the output load.

[0043] In this embodiment, the output load is load transistor M5 and load transistor M6. The gates of load transistors M5 and M6 are respectively connected to the drains of P-type input transistors M1 and M2, and the drains of load transistors M5 and M6 are respectively connected to the sources of N-type input transistors M3 and M4. The transconductance of P-type input transistors M1, M2, M3, and M4 is added together and then converted into voltage by load transistors M5 and M6 and output at the output terminal.

[0044] In this embodiment, the amplifier doubles its transconductance and reduces noise under the same bias current. Although the input operating mode voltage range of the amplifier in this embodiment is relatively small, because in this embodiment, AC signals can simultaneously enter from the positive and negative input terminals V... INP V INN Input, common-mode voltage V at the input terminal IN,CM The amplitude will be significantly reduced, ideally to zero. Therefore, the entire circuit can adopt the amplifier structure in this embodiment.

[0045] In this embodiment, because it has a smaller requirement for feedback capacitance, the equivalent capacitance C of the microphone is... MEMS Less than 2pF.

[0046] Compared with related technologies, the present invention maintains the microphone C by introducing a bias resistor and combining it with a feedback resistor. MEMS The two ends are high impedance, and the coupling capacitor CAC Both ends of the amplifier are also high impedance, so the AC signal can pass through the amplifier's V... INP and V INN Input at both ends. Coupling capacitor C AC After AC coupling of the input signal, it enters V INN Microphone C MEMS It will find an internal equilibrium point. When the closed-loop gain is 1, C FB =2C MEMS Therefore, the feedback capacitor C FB It can be compared to C MEMS Doubling the size allows for greater filtering of the amplifier's own noise, thus improving the overall signal-to-noise ratio of the system.

[0047] In one embodiment, because the AC signal can simultaneously originate from the positive and negative input terminals V INP V INN Input, common-mode voltage V at the input terminal IN,CM The amplitude will be significantly reduced, ideally even to zero. Therefore, a current-reuse amplifier (CR-Amp) with a relatively small input common-mode voltage range can be used.

[0048] In one embodiment, the input terminal of the CR-Amp can simultaneously obtain the transconductance of both P-type and N-type inputs under the same current bias, thereby increasing the input transconductance by approximately double, thus reducing the amplifier noise and improving the signal-to-noise ratio of the entire system.

[0049] The above description is merely an embodiment of the present invention. It should be noted that those skilled in the art can make improvements without departing from the inventive concept of the present invention, but these improvements all fall within the protection scope of the present invention.

Claims

1. A single-ended to differential microphone circuit, characterized in that, include: An amplifier, a microphone whose output is connected to the positive input of the amplifier, and a coupling capacitor C whose output is connected to the negative input of the amplifier. AC The first feedback capacitor C connected between the negative output terminal and the positive input terminal of the amplifier FB1 , and the first feedback capacitor C FB1 The first feedback resistor R in parallel FB1 The second feedback capacitor C is connected between the positive output terminal and the negative input terminal of the amplifier. FB2 and the second feedback capacitor C FB2 The second feedback resistor R in parallel FB2 The amplifier is a current-shared amplifier. The microphone and the input terminal of the coupling capacitor are connected to a bias resistor R. B The bias resistor R B This allows an AC signal to be simultaneously input to both the positive and negative input terminals of the amplifier, via the bias resistor R. B A bias voltage is supplied to the microphone and the input terminal of the coupling capacitor; The amplifier includes: P-type input transistor M1, P-type input transistor M2, N-type input transistor M3, N-type input transistor M4, and an output load; The sources of the P-type input transistors M1 and M2 are connected to the bias current IB. The gates of the P-type input transistors M1 and M2 are connected to the positive and negative input terminals of the amplifier, respectively. The drains of the N-type input transistors M3 and M4 are connected to the drains of the P-type input transistors M1 and M2, respectively. The gates of the N-type input transistors M3 and M4 are connected to the positive and negative input terminals of the amplifier, respectively. The sources of the N-type input transistors M3 and M4 are connected to the output load.

2. The single-ended to differential microphone circuit according to claim 1, characterized in that, Coupling capacitor C AC The capacitance is at least four times that of the microphone.

3. The single-ended to differential microphone circuit according to claim 1, characterized in that, The output load is load transistor M5 and load transistor M6. The gates of load transistor M5 and load transistor M6 are respectively connected to the drains of P-type input transistor M1 and P-type input transistor M2, and the drains of load transistor M5 and load transistor M6 are respectively connected to the sources of N-type input transistor M3 and N-type input transistor M4. The transconductances of the P-type input transistor M1, P-type input transistor M2, N-type input transistor M3, and N-type input transistor M4 are added together and then converted into voltage by the load transistors M5 and M6, which is output at the output terminal.

4. The single-ended to differential microphone circuit according to claim 1, characterized in that, The equivalent capacitance of the microphone is less than 2pF.

5. An electronic device comprising a single-ended to differential microphone circuit, characterized in that, The single-ended to differential microphone circuit includes: an amplifier, a microphone whose output is connected to the positive input of the amplifier, and a coupling capacitor C whose output is connected to the negative input of the amplifier. AC The first feedback capacitor C connected between the negative output terminal and the positive input terminal of the amplifier FB1 , and the first feedback capacitor C FB1 The first feedback resistor R in parallel FB1 The second feedback capacitor C is connected between the positive output terminal and the negative input terminal of the amplifier. FB2 and the second feedback capacitor C FB2 The second feedback resistor R in parallel FB2 The amplifier is a current-shared amplifier. The microphone and the input terminal of the coupling capacitor are connected to a bias resistor R. B The bias resistor R B This allows an AC signal to be simultaneously input to both the positive and negative input terminals of the amplifier, via the bias resistor R. B A bias voltage is supplied to the microphone and the input terminal of the coupling capacitor; The amplifier includes: P-type input transistor M1, P-type input transistor M2, N-type input transistor M3, N-type input transistor M4, and an output load; The sources of the P-type input transistors M1 and M2 are connected to the bias current IB. The gates of the P-type input transistors M1 and M2 are connected to the positive and negative input terminals of the amplifier, respectively. The drains of the N-type input transistors M3 and M4 are connected to the drains of the P-type input transistors M1 and M2, respectively. The gates of the N-type input transistors M3 and M4 are connected to the positive and negative input terminals of the amplifier, respectively. The sources of the N-type input transistors M3 and M4 are connected to the output load.

6. The electronic device according to claim 5, characterized in that, Coupling capacitor C AC The capacitance is at least four times that of the microphone.

7. The electronic device according to claim 5, characterized in that, The output load is load transistor M5 and load transistor M6. The gates of load transistor M5 and load transistor M6 are respectively connected to the drains of P-type input transistor M1 and P-type input transistor M2, and the drains of load transistor M5 and load transistor M6 are respectively connected to the sources of N-type input transistor M3 and N-type input transistor M4. The transconductances of the P-type input transistor M1, P-type input transistor M2, N-type input transistor M3, and N-type input transistor M4 are added together and then converted into voltage by the load transistors M5 and M6, which is output at the output terminal.

8. The electronic device according to claim 5, characterized in that, The equivalent capacitance of the microphone is less than 2pF.

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