Detection circuit for a microelectromechanical sensor

Abstract

The present disclosure utilizes a voltage-to-voltage converter to apply positive and negative feedback voltages to an electromechanical sensor of a microphone to facilitate an increase in microphone sensitivity and a reduction in distortion. A microphone includes an electromechanical sensor including a capacitive detection element including a first detection node and a second detection node; and a voltage-to-voltage converter including an input, a first output, and a second output. The voltage-to-voltage converter forms a negative feedback loop between the first output and the input of the voltage-to-voltage converter by coupling a first capacitance to the second detection node. The first detection node is electrically coupled to the input of the voltage-to-voltage converter, and the voltage-to-voltage converter forms a positive feedback loop between the second output and the input of the voltage-to-voltage converter by coupling a second capacitance to the first detection node.

Description

[0001] Citation of relevant applications

[0002] This patent application claims priority to U.S. Nonprovisional Patent Application No. 18 / 753,886, filed June 25, 2024, entitled “A SENSING CIRCUIT OF A MICRO-ELECTROMECHANICAL SENSOR”, and to U.S. Provisional Patent Application No. 63 / 567,354, filed March 19, 2024, entitled “APPLYING APOSITIVE FEEDBACK VOLTAGE TO AN ELECTROMECHANICAL SENSOR UTILIZING A VOLTAGE-TO-VOLTAGE CONVERTER TO FACILITATE A REDUCTION OF CHARGE FLOW IN SUCH SENSORREPRESENTING SPRING SOFTENING”, the entire application of which is incorporated herein by reference. Technical Field

[0003] This disclosure generally relates to embodiments of an electromechanical sensor for a microphone that utilizes a voltage-to-voltage (V2V) converter to apply positive and negative feedback voltages to the microphone in order to improve microphone sensitivity and reduce distortion. Background Technology

[0004] Traditional microphone technology is susceptible to distortion due to the electrical coupling between capacitive loads and / or other parasitic circuit elements and the output of the microphone's electromechanical sensing elements (e.g., capacitive sensing elements). Furthermore, the sensitivity of the electromechanical sensing element to detecting changes in sound pressure level can vary due to die stress, such as assembly differences, variations in operating temperature, changes in operation over time, or other environmental conditions that affect the resonant frequency and gain of the electromechanical sensing element. In this respect, traditional sensor technology suffers from several drawbacks, some of which can be understood with reference to the various embodiments described below. Summary of the Invention

[0005] This disclosure provides a microphone, comprising: an electromechanical sensor including a capacitive sensing element, the capacitive sensing element including a first capacitive sensing element node and a second capacitive sensing element node; and a voltage-to-voltage converter including a voltage-to-voltage converter input, a first voltage-to-voltage converter output, and a second voltage-to-voltage converter output, wherein the second capacitive sensing element node is electrically coupled to the voltage-to-voltage converter input, wherein the voltage-to-voltage converter forms a negative feedback loop between the first voltage-to-voltage converter output and the voltage-to-voltage converter input, wherein the negative feedback loop is electrically coupled to the first capacitive sensing element node via the first capacitive coupling, wherein the voltage-to-voltage converter forms a positive feedback loop between the second voltage-to-voltage converter output and the voltage-to-voltage converter input via an amplifier having a gain greater than 1, and wherein the positive feedback loop is electrically coupled to the second capacitive sensing element node via the second capacitive coupling.

[0006] This disclosure also provides a microphone, comprising: an electromechanical sensor including a capacitive sensing element, the capacitive sensing element including a first capacitive sensing element node and a second capacitive sensing element node; and a voltage-to-voltage converter including a voltage-to-voltage converter input and a voltage-to-voltage converter output, wherein the second capacitive sensing element node is electrically coupled to the voltage-to-voltage converter input, wherein the voltage-to-voltage converter forms a negative feedback loop between the voltage-to-voltage converter output and the voltage-to-voltage converter input, wherein the negative feedback loop is electrically coupled to the first capacitive sensing element node via capacitive coupling, and wherein the voltage-to-voltage converter output represents a sound pressure change detected by the capacitive sensing element.

[0007] This disclosure also provides a microphone, comprising: an electromechanical sensor including a capacitive sensing element, the capacitive sensing element including a first capacitive sensing element node and a second capacitive sensing element node; and a voltage-to-voltage converter including a voltage-to-voltage converter input and a voltage-to-voltage converter output, wherein the second capacitive sensing element node is electrically coupled to the voltage-to-voltage converter input, wherein the voltage-to-voltage converter forms a negative feedback loop between the voltage-to-voltage converter output and the voltage-to-voltage converter input, wherein the negative feedback loop is electrically coupled to the first capacitive sensing element node; and wherein the voltage-to-voltage converter output represents a sound pressure change detected by the capacitive sensing element.

[0008] This disclosure also provides a microphone, comprising: an electromechanical sensor including a capacitive sensing element, the capacitive sensing element including a first capacitive sensing element node and a second capacitive sensing element node; a bias resistor electrically coupling a bias voltage to the second capacitive sensing element node; and a voltage-to-voltage converter including a voltage-to-voltage converter input, a first voltage-to-voltage converter output, and a second voltage-to-voltage converter output, wherein the second capacitive sensing element node is electrically coupled to the voltage-to-voltage converter input via a blocking capacitor, wherein the voltage-to-voltage converter forms a negative feedback loop between the first voltage-to-voltage converter output and the voltage-to-voltage converter input, wherein the negative feedback loop is electrically coupled to the first capacitive sensing element node, wherein the voltage-to-voltage converter forms a positive feedback loop between the second voltage-to-voltage converter output and the voltage-to-voltage converter input via an amplifier including a gain greater than 1, and wherein the positive feedback loop is electrically coupled to the second capacitive sensing element node via capacitive coupling. Attached Figure Description

[0009] Non-limiting embodiments of this disclosure are described with reference to the following accompanying drawings, in which, unless otherwise stated, the same reference numerals denote the same parts in the various views:

[0010] Figure 1 A block diagram showing a portion of a microphone according to various exemplary embodiments is provided, wherein a positive feedback voltage and a negative feedback voltage are applied to the microphone’s electromechanical sensors using a V2V converter to promote a reduction in distortion and an increase in the microphone’s sensitivity to detecting changes in sound pressure.

[0011] Figure 2 A block diagram showing a portion of a microphone according to various exemplary embodiments is provided, wherein positive feedback voltage and negative feedback voltage are applied to the microphone’s electromechanical sensors via corresponding capacitive coupling, the electromechanical sensors utilizing V2V converters to facilitate distortion reduction and improve the microphone’s sensitivity to detecting changes in sound pressure.

[0012] Figure 3 A block diagram of a negative feedback loop for a portion of a microphone according to various exemplary embodiments is shown, wherein a positive feedback voltage and a negative feedback voltage are applied to an electromechanical sensor of the microphone via respective capacitive couplings, the electromechanical sensor utilizing a V2V converter to facilitate a reduction in distortion and an increase in the microphone’s sensitivity to detecting changes in sound pressure.

[0013] Figure 4A block diagram of a positive feedback loop of a microphone section structure according to various exemplary embodiments is shown, wherein a positive feedback voltage and a negative feedback voltage are applied to an electromechanical sensor of the microphone via corresponding capacitive coupling, the electromechanical sensor utilizing a V2V converter to facilitate the reduction of distortion and the improvement of the microphone’s sensitivity to detecting changes in sound pressure.

[0014] Figure 5 A block diagram of a microphone section structure is shown according to various exemplary embodiments, wherein the negative feedback path and positive feedback path of the microphone are capacitively coupled to their respective electromechanical sensors, both modeled by Thevenin equivalent circuits.

[0015] Figure 6 A block diagram is shown as part of a microphone modeled as a differential circuit according to various exemplary embodiments, wherein the capacitive couplings of the negative feedback path and the positive feedback path of the electromechanical sensor of the microphone via the V2V converter are modeled by the Thevenin equivalent circuit, and wherein the inputs of the amplifier of the V2V converter include AC noise sources.

[0016] Figure 7 The diagram shows the frequency response of a negative feedback loop representing a portion of a microphone according to various exemplary embodiments, wherein the negative feedback voltage of said portion of the microphone is applied to an electromechanical sensor of the microphone via a corresponding capacitive coupling, the electromechanical sensor utilizing a V2V converter to facilitate the reduction of distortion and the improvement of the microphone’s sensitivity to detecting changes in sound pressure.

[0017] Figure 8 The diagram shows the frequency response of a positive feedback loop representing a portion of a microphone according to various exemplary embodiments, wherein the positive and negative feedback voltages of said portion of the microphone are applied to the microphone’s electromechanical sensors via corresponding capacitive couplings, the electromechanical sensors utilizing V2V converters to facilitate reduction of distortion and increase of the microphone’s sensitivity relative to detecting changes in sound pressure.

[0018] Figure 9 and Figure 10 A block diagram of a portion of a microphone according to various exemplary embodiments is shown, wherein the corresponding capacitive couplings of the negative feedback path and the positive feedback path to the electromechanical sensor of the microphone are implemented as a switching voltage divider to facilitate modification of the microphone's circuit gain, thereby changing the microphone's sensitivity relative to the detection of changes in sound pressure.

[0019] Figure 11A block diagram of a portion of a microphone according to various exemplary embodiments is shown, wherein the microphone’s electromechanical sensor includes a single-ended output corresponding to a negative feedback loop coupled to the electromechanical sensor via a V2V converter to facilitate reduction of distortion and increase of the microphone’s sensitivity to detecting changes in sound pressure.

[0020] Figure 12 A block diagram showing a portion of a microphone according to various exemplary embodiments is provided, wherein a positive feedback voltage and a negative feedback voltage are applied to an electromechanical sensor using a V2V converter, and wherein the nodes of the capacitive sensing element of the electromechanical sensor are electrically coupled to the input of the V2V converter via a blocking capacitor to facilitate the reduction of distortion and the improvement of the microphone’s sensitivity to the detection of changes in sound pressure.

[0021] Figure 13 A block diagram showing a portion of another microphone according to various exemplary embodiments is provided, wherein positive feedback voltage and negative feedback voltage are applied to the microphone’s electromechanical sensor via a blocking capacitor, utilizing a V2V converter to facilitate distortion reduction and improve the microphone’s sensitivity relative to detecting changes in sound pressure.

[0022] Figure 14 A block diagram showing a portion of a microphone according to various exemplary embodiments is provided, wherein the microphone’s electromechanical sensor includes a single-ended output corresponding to a negative feedback loop coupled to the electromechanical sensor via a V2V converter to facilitate modification of the microphone’s circuit gain, thereby altering the microphone’s sensitivity relative to detecting changes in sound pressure.

[0023] Figure 15 A block diagram showing a portion of another microphone according to various exemplary embodiments is provided, wherein the microphone’s electromechanical sensor includes a single-ended output corresponding to a negative feedback loop coupled to the electromechanical sensor via a V2V converter and a blocking capacitor, to facilitate modification of the microphone’s circuit gain, thereby altering the microphone’s sensitivity relative to detecting changes in sound pressure.

[0024] Figure 16 A block diagram of a portion of a microphone according to various exemplary embodiments is shown, wherein a positive feedback voltage and a negative feedback voltage are applied to an electromechanical sensor using a V2V converter, wherein the node of the capacitive sensing element of the electromechanical sensor and the negative feedback loop are electrically coupled to the input of the V2V converter to facilitate the reduction of distortion and the improvement of the microphone’s sensitivity to sensing changes in sound pressure, and wherein a phase lead circuit is included in the negative feedback loop. Detailed Implementation

[0025] Various aspects of this disclosure will now be described more fully with reference to the accompanying drawings, in which exemplary embodiments are illustrated. In the following description, numerous specific details are set forth for purposes of explanation in order to provide a thorough understanding of the various embodiments. However, this subject matter disclosure can be embodied in many different forms and should not be construed as limited to the exemplary embodiments described herein.

[0026] As mentioned above, conventional microphone technology is prone to distortion due to capacitive loads and / or other circuit parasitic elements electrically coupling to the output of the microphone's electromechanical sensing element. Furthermore, the voltage sensitivity of the force and pressure applied to the diaphragm of a conventional microphone's sensing element is limited by the diaphragm's stiffness (e.g., k) and / or the amount of reduction in the bias voltage applied to the sensing element to affect its sensitivity.

[0027] The various embodiments disclosed herein can improve the sensitivity, reduce distortion, improve stability, and / or prevent microphone overload or clipping by applying positive and negative feedback voltages to the electromechanical sensors of the microphone using a V2V converter, respectively, via positive and negative feedback loops.

[0028] For example, such embodiments can: improve microphone stability using a phase-lead circuit via a negative feedback loop; modify microphone sensitivity using corresponding gain-switching circuits via positive and negative feedback loops, for example, by increasing the overall microphone sensitivity to compensate for the decrease in electromechanical sensor sensitivity, and / or by reducing the overall microphone sensitivity to compensate for the high sound pressure applied to the electromechanical sensor, thereby preventing microphone overload, such as by chopping; and / or provide a negative capacitive load to the electromechanical sensor via a positive feedback loop to reduce distortion.

[0029] For example, in some embodiments, the microphone includes an electromechanical sensor (e.g., a MEMS sensor) and a V2V converter. The electromechanical sensor includes a capacitive sensing element comprising a first capacitive sensing element node and a second capacitive sensing element node. The V2V converter includes a V2V converter input, a first V2V converter output, and a second V2V converter output.

[0030] The second capacitive sensing element node is electrically coupled to the V2V converter input, and the V2V converter forms a negative feedback loop between the first V2V converter output and the V2V converter input. The negative feedback loop is electrically coupled to the first capacitive sensing element node via the first capacitive coupling.

[0031] Furthermore, the V2V converter forms a positive feedback loop between the output and input of the second V2V converter through an amplifier with a gain greater than 1; and the positive feedback loop is electrically coupled to the node of the second capacitive sensing element via a second capacitive coupling.

[0032] In other embodiments, the first capacitive coupling and / or the second capacitive coupling may include a capacitive voltage divider, a resistive voltage divider, and / or an amplifier.

[0033] In another embodiment, the output of the electromechanical sensor may include the voltage difference between the output of the first V2V converter and the output of the second V2V converter, and represent the sound pressure change detected by the capacitive sensing element.

[0034] In some embodiments, the positive feedback loop reduces signal distortion of the electromechanical sensor output, for example, by reducing the load capacitance electrically coupled to the capacitive sensing element. In other embodiments, the positive feedback loop reduces the load capacitance by electrically coupling a negative capacitance to the capacitive sensing element. In yet another embodiment, to generate the negative capacitance, the positive feedback loop includes a defined positive loop gain in conjunction with the feedback capacitance of the positive feedback loop.

[0035] In other embodiments, the negative feedback loop includes a voltage divider and modifies the sensitivity of the electromechanical sensor's output relative to changes in sound pressure detected by the capacitive sensing element. The output includes the voltage difference between the outputs of a first V2V converter and a second V2V converter. In some embodiments, the negative feedback loop modifies the sensitivity by adjusting the circuit gain of the electromechanical sensor.

[0036] In another embodiment, the first capacitive coupling includes a first capacitive voltage divider; the second capacitive coupling includes a second capacitive voltage divider; and the circuit gain of the electromechanical sensor is modified by altering the gain of the corresponding small-signal capacitors of the first and second capacitive voltage dividers. In one embodiment, the gain of the corresponding small-signal capacitors is modified by switching the corresponding capacitors of the first and second capacitive voltage dividers to ground.

[0037] In other embodiments, the microphone further includes a bias circuit that applies a bias voltage to a node of a first capacitive sensing element, wherein the bias voltage sets the operating node of the capacitive sensing element to a negative capacitance region.

[0038] In another embodiment, the V2V converter includes an inverting amplifier and a phase-leading circuit, wherein the V2V input is electrically coupled to the inverting amplifier input, and wherein the negative feedback loop includes the inverting amplifier and the phase-leading circuit. In one embodiment, the inverting amplifier includes the phase-leading circuit.

[0039] In some embodiments, the V2V converter includes a unity-gain inverting amplifier and a low-pass filter (LPF), with the circuit output corresponding to the phase-leading circuit electrically coupled to the circuit input corresponding to the unity-gain inverting amplifier. In this respect, the positive feedback loop includes an inverting amplifier, a phase-leading circuit, a unity-gain inverting amplifier, and an LPF. In one embodiment, the unity-gain inverting amplifier includes an LPF.

[0040] In other embodiments, a bias voltage, such as + / - 5-50 volts, is applied to the second capacitive sensing element node via a bias resistor (e.g., using a bias circuit). The second capacitive sensing element node is electrically coupled to the V2V converter input via a blocking capacitor, for example, to isolate the V2V converter from the direct connection of the bias voltage.

[0041] In another embodiment, the microphone includes: an electromechanical sensor including a capacitive sensing element, the capacitive sensing element including a first capacitive sensing element node and a second capacitive sensing element node; and a V2V converter including a V2V converter input and a V2V converter output.

[0042] The second capacitive sensing element node is electrically coupled to the V2V converter input; the V2V converter forms a negative feedback loop between its output and input. This negative feedback loop is then electrically coupled to the first capacitive sensing element node via capacitive coupling; the V2V converter output represents the sound pressure change detected by the capacitive sensing element.

[0043] In some embodiments, capacitive coupling includes a capacitive voltage divider, a resistive voltage divider, and / or an amplifier.

[0044] In other embodiments, the negative feedback loop includes a voltage divider and modifies the sensitivity of the V2V converter output relative to the detection of sound pressure changes. In one embodiment, the negative feedback loop modifies the sensitivity by adjusting the circuit gain of the electromechanical sensor.

[0045] In another embodiment, the microphone further includes a bias circuit that applies a bias voltage to the detection node of the first capacitive sensing element, and the bias voltage sets the operating node of the capacitive sensing element to a negative capacitance region.

[0046] In some embodiments, the V2V converter includes an inverting amplifier and a phase-leading circuit; the V2V converter input is electrically coupled to the inverting amplifier input; the negative feedback loop includes an inverting amplifier and a phase-leading circuit. In one embodiment, the inverting amplifier includes a phase-leading circuit.

[0047] In other embodiments, the circuit gain of the electromechanical sensor is modified by altering the gain of the small-signal capacitor in the capacitive voltage divider. In one embodiment, the small-signal capacitor gain is modified by switching the capacitor of the capacitive voltage divider to ground.

[0048] In another embodiment, a bias voltage is applied to the second capacitive sensing element node via a bias resistor, for example using a bias circuit, and the V2V converter input is electrically coupled to the second capacitive sensing element node via a blocking capacitor.

[0049] In some embodiments, the microphone includes: an electromechanical sensor including a capacitive sensing element, the capacitive sensing element including a first capacitive sensing element node and a second capacitive sensing element node; and a V2V converter including a V2V converter input and a V2V converter output.

[0050] The second capacitive sensing element node is electrically coupled to the V2V converter input; the V2V converter forms a negative feedback loop between its output and input. This negative feedback loop is electrically coupled to the first capacitive sensing element node; the V2V converter output represents the sound pressure change detected by the capacitive sensing element.

[0051] In other embodiments, the V2V converter includes an inverting amplifier and a phase-leading circuit; the V2V converter input is electrically coupled to the inverting amplifier input; the negative feedback loop includes an inverting amplifier and a phase-leading circuit. In one embodiment, the inverting amplifier includes a phase-leading circuit.

[0052] In another embodiment, a bias voltage is applied to the second capacitive sensing element node via a bias resistor, for example using a bias circuit; and the V2V converter input is electrically coupled to the second capacitive sensing element node via a blocking capacitor.

[0053] In some embodiments, the microphone includes an electromechanical sensor, which includes a capacitive sensing element, the capacitive sensing element including a first capacitive sensing element node and a second capacitive sensing element node; a bias resistor that electrically couples a bias voltage to the second capacitive sensing element node; and a V2V converter that includes a V2V converter input, a first V2V converter output, and a second V2V converter output.

[0054] The second capacitive sensing element node is electrically coupled to the V2V converter input via a blocking capacitor; and the V2V converter forms a negative feedback loop between the first V2V converter output and the V2V converter input. The negative feedback loop is electrically coupled to the first capacitive sensing element node.

[0055] The V2V converter forms a positive feedback loop between the output and input of the second V2V converter through an amplifier with a gain greater than 1; and the positive feedback loop is electrically coupled to the node of the second capacitive sensing element via capacitive coupling.

[0056] In other embodiments, capacitive coupling includes a capacitive voltage divider, a resistive voltage divider, and / or an amplifier.

[0057] In another embodiment, the output of the electromechanical sensor includes the voltage difference between the output of the first V2V converter and the output of the second V2V converter, and represents the change in sound pressure detected by the capacitive sensing element.

[0058] In some embodiments, the positive feedback loop reduces signal distortion at the output of the electromechanical sensor. In one embodiment, the positive feedback loop reduces signal distortion by reducing the load capacitance electrically coupled to the capacitive sensing element.

[0059] In other embodiments, the positive feedback loop reduces the load capacitance by electrically coupling a negative capacitance to a capacitive sensing element.

[0060] In another embodiment, the V2V converter includes an inverting amplifier and a phase-leading circuit; the V2V converter input is electrically coupled to the inverting amplifier input; the negative feedback loop includes an inverting amplifier and a phase-leading circuit. In one embodiment, the inverting amplifier includes a phase-leading circuit.

[0061] In some embodiments, the V2V converter includes a unity-gain inverting amplifier and an LPF; a circuit output corresponding to a phase-leading circuit is electrically coupled to a circuit input corresponding to a unity-gain inverting amplifier; and a positive feedback loop includes a unity-gain inverting amplifier and an LPF.

[0062] In other embodiments, the circuit output corresponding to the phase-leading circuit is electrically coupled to the circuit input corresponding to the unity-gain inverting amplifier. In one embodiment, the unity-gain inverting amplifier includes an LPF.

[0063] Now for reference Figures 1 to 4 According to various exemplary embodiments, a block diagram (100-400) of a portion of a microphone 102 is shown, wherein a positive feedback voltage and a negative feedback voltage are applied to the capacitive detection element (112) of an electromechanical sensor (110), which utilizes a V2V converter (120) to facilitate the reduction of distortion and the improvement of the microphone’s sensitivity to changes in sound pressure.

[0064] The electromechanical sensor includes a capacitive sensing element (112), which includes a first capacitive sensing element node and a second capacitive sensing element node. A first bias circuit (202) is connected via a first bias resistor (“R”). a(For example, a high-impedance element (e.g., >1 GΩ)) applies a first bias voltage ("V") to the node of the second capacitive sensing element. a In some embodiments, V a It is grounded (0 volts), or in a standard (e.g., complementary metal-oxide-semiconductor (CMOS)) or positive (e.g., "V") state. dd ) and negative (e.g., "V") ss "" The reference voltage between the power supply voltages.

[0065] The second bias circuit (204) (e.g., a charge pump) passes through the second bias resistor (“R”). b A second bias voltage (“V”) is applied to the node of the first capacitive sensing element by a high-impedance element (e.g., >1 GΩ). b (That is, the voltage generated by the charge pump is much greater than the first bias voltage, for example, 5-50 volts), which sets the operating node of the capacitive sensing element to the negative capacitance region.

[0066] In some embodiments, the second bias circuit can be actively or passively controlled to bias the capacitive sensing element to a defined bias point, for example, corresponding to a target value of charge to be placed on the capacitive sensing element.

[0067] The V2V converter includes a V2V converter input (“VIN”), a first V2V converter output (“VOUT1”), and a second V2V converter output (“VOUT2”). In some embodiments, the output of the electromechanical sensor includes the voltage difference between the first V2V converter output and the second V2V converter output, and represents the change in sound pressure detected by the capacitive sensing element.

[0068] The V2V converter input is electrically coupled to the second capacitive sensing element node; and the V2V converter forms a negative feedback loop (130) between the first V2V converter output and the V2V converter input. The negative feedback loop (130) is electrically coupled to the first capacitive sensing element node via a first capacitive coupling (214). In some embodiments, the first capacitive coupling (214) includes a capacitive voltage divider (e.g., via "C"). g0 "and "C g1 "), resistive voltage dividers and / or amplifiers (not shown).

[0069] In one embodiment, C g0 This includes parasitic capacitors and / or additional capacitors (not shown) coupled to the negative feedback loop / first capacitive sensing element node.

[0070] In another embodiment, C g1Provides a negative feedback path, negative feedback voltage and / or coupling, and acts as a blocking capacitor to isolate / disconnect the higher voltage, biased first capacitive sensing element node from the lower voltage node (e.g., the output of a V2V converter).

[0071] The V2V converter also includes an inverting amplifier (206) electrically coupled to a phase-lead circuit (208) (e.g., including a negative gain (“-A”)). In one embodiment (not shown), the inverting amplifier includes a phase-lead circuit. The V2V converter input is electrically coupled to the inverting amplifier input, and the negative feedback loop includes the inverting amplifier and the phase-lead circuit.

[0072] Furthermore, the V2V converter includes a unity-gain inverting amplifier (210) and an LPF (212), with the circuit output corresponding to the phase-leading circuit electrically coupled to the input corresponding to the unity-gain inverting amplifier. In this respect, the V2V converter forms a positive feedback loop (140) between the second V2V converter output and the V2V converter input by an amplifier including a gain greater than 1 (e.g., an amplifier including an inverting amplifier and a unity-gain inverting amplifier). In some embodiments, the unity-gain inverting amplifier includes an LPF.

[0073] The positive feedback loop is electrically coupled to the second capacitive sensing element node via a second capacitive coupling (216). In some embodiments, the second capacitive coupling includes a capacitive voltage divider (e.g., via "C"). a0 "and "C a1 ( ), resistive voltage divider (not shown) and / or amplifier (not shown).

[0074] In one embodiment, Ca0 includes the amplifier input capacitance of the inverting amplifier (206), parasitic capacitors, and / or additional capacitors (not shown) coupled to the positive feedback loop / second capacitive sensing element node.

[0075] In another embodiment, C a1 Provides a positive feedback path, positive feedback voltage and / or coupling, and acts as a blocking capacitor to isolate / disconnect the higher voltage, biased first capacitive sensing element node from the lower voltage node (e.g., the output) of the V2V converter.

[0076] Figure 5A block diagram (500) of a portion (102) of a microphone (not shown) according to various exemplary embodiments is illustrated, showing the corresponding capacitive couplings (214, 216) of the negative and positive feedback paths (130, 140) of the microphone's electromechanical sensor (112) modeled via a Thevenin equivalent circuit. In this respect, the first capacitive coupling (214), such as a capacitive voltage divider, can be modeled via a Thevenin equivalent circuit, which includes series electrical coupling to a capacitor (“C…”) according to the following… g Gain level ("G1") of )

[0077]

[0078] .

[0079] Furthermore, the second capacitive coupling (216), such as a capacitive voltage divider, can be modeled using a Thevenin equivalent circuit, which includes series electrical coupling to a capacitor (“C”). a The gain stage (“G2”) is shown below:

[0080] ,

[0081] .

[0082] Figures 6-9 The following provides an analysis of the operation and performance (e.g., small signal analysis) of the embodiments described herein, which involve using a V2V converter to apply positive and negative feedback voltages to an electromechanical sensor of a microphone to facilitate distortion reduction and microphone sensitivity improvement.

[0083] The capacitance sensing element (112) is a variable capacitor, comprising: a first electrode mechanically coupled to the membrane; and a capacitor (e.g., a MEMS capacitor) formed with the first electrode. MEMS The second electrode of the membrane, wherein the first electrode and the second electrode are separated by a gap that changes as the membrane and the first electrode move in response to forces and pressures applied to the membrane.

[0084] MEMS capacitor operation:

[0085] MEMS capacitance depends on the electrode area (A) and the gap (g), as shown below:

[0086] .

[0087] The gap depends on the initial gap (g0), the external force (F, i.e., sound pressure), the electrostatic force (q) generated by the charge, and the membrane stiffness (k), as shown below:

[0088] .

[0089] The gap decreases with charge, while the capacitance increases with charge.

[0090] The voltage across a MEMS capacitor depends on the charge and the MEMS capacitance, as shown below:

[0091] .

[0092] Voltage changes with charge q.

[0093] Voltage varies depending on the force or sound pressure, expressed as F.

[0094] If the charge q is constant, then the change in voltage is linearly related to the change in force (F).

[0095] distortion:

[0096] By C l The capacitive load represented may be caused by the capacitive impedance of the electronic circuitry coupled to the MEMS capacitor, parasitic capacitance, and non-ideal mechanical behavior of the MEMS capacitor (such as bending of the first electrode).

[0097] If the total charge on the MEMS capacitor (q) t If the capacitive load on the MEMS capacitor remains constant, the capacitive load on the MEMS capacitor may cause distortion.

[0098] The charge q on the MEMS capacitor depends on the total charge, the voltage across the MEMS capacitor, and the capacitive load, as shown below:

[0099] ,

[0100] This leads to a nonlinear relationship between voltage and force, which depends on C. l As shown below (where nonlinear relationships cause distortion):

[0101] .

[0102] Small signal analysis:

[0103] The relationship between charge, voltage, and force in a capacitive sensing element is as follows: .

[0104] When biased, electromechanical sensors and capacitive sensing elements typically operate under small disturbances at the bias point. Therefore, as Figure 6 As shown, a capacitive sensing element can be represented as a small-signal voltage source and a small-signal capacitor, as shown below:

[0105] ,

[0106] .

[0107] Based on the above, V sig and C sig The values ​​of each increase with increasing charge q; when charge q is sufficient, C sig It can become negative. In this respect, negative capacitance includes small-signal low-frequency capacitance represented by the slope of the line (e.g., a negative slope), where the slope represents a small change in charge and a small change in the voltage of the capacitive sensing element. The operation of the capacitive sensing element in the negative capacitance region (i.e., when C...) sig When the value is negative, it is unstable. In some embodiments, providing active feedback enables the capacitive sensing element to operate stably.

[0108] Furthermore, the V of the force and pressure (e.g., sound pressure) applied to the membrane of the capacitive sensing element sig Sensitivity is limited by the membrane stiffness k and / or the bias voltage applied to the capacitive sensing element, which limits the charge that may be present on the capacitive element of interest. To address V sig To address this reduced sensitivity to force and pressure, the embodiments disclosed herein provide a gain boost circuit configuration to increase and / or modify V. sig Sensitivity to force and pressure.

[0109] like Figure 6 As further shown, the small signal model of the microphone section includes an AC noise source (610 ("V") n1 ”), 620 (“V”) n2 Furthermore, phase lead (208) and LPF (212) were removed from the small signal model because the gains corresponding to phase lead and LPF are uniform in the signal band.

[0110] The capacitive load on a capacitive sensing element causes distortion of the corresponding output signal. The capacitive load on a capacitive sensing element also generates additional noise. The load capacitance electrically coupled to the capacitive sensing element represents the capacitive load from the circuit coupled to the capacitive sensing element:

[0111] .

[0112] Due to positive feedback loops (including "-A", "-1", "G2" and "C") a "),if And C a It is large enough that the capacitive load can be ≤0 to meet the distortion requirements.

[0113] V sig V n1 and Vn2 The resulting differential output is:

[0114] .

[0115] Gain Boost: For values ​​of A > 1 and G1 and G2 between 0 and 1, the circuit output relative to V... sig He was promoted.

[0116] Regarding noise reduction and cancellation:

[0117] For a larger C sig Value, relative to signal V sig V n1 and V n2 The noise contribution is reduced.

[0118] If C sig If it is biased as a negative capacitor, then Amplifier noise V n1 The difference is eliminated and the differential output becomes:

[0119] .

[0120] If G1=G2=G, then the inverting amplifier noise V n2 This is also eliminated, and the differential output becomes:

[0121] .

[0122] In this regard, in some embodiments, the positive feedback loop reduces signal distortion of the electromechanical sensor output, for example, by reducing the load capacitance electrically coupled to the capacitive sensing element, for example by electrically coupling a negative capacitance to the capacitive sensing element.

[0123] Figure 7 Bode plot / figure (700) representing the frequency response of the negative feedback loop is shown. The element has a resonant frequency and Q due to the mass, stiffness (k), and damping of the membrane in the capacitive sensing element.

[0124] At high frequencies, the membrane does not move, and the capacitance of the capacitive sensing element depends only on the bias point of the capacitive sensing element, as expressed as:

[0125] .

[0126] Conversely, the small-signal behavior of a capacitive sensing element at frequency can be approximated by the following transfer function:

[0127] ,

[0128] .

[0129] A phase-leading circuit is needed to stabilize the negative feedback loop. A preferred embodiment includes a phase-leading circuit in the inverting amplifier because additional noise from the phase-leading circuit is added to V. n1 And by C sig offset.

[0130] The negative feedback loop includes G1 and C. g C sig Inverting amplifier and phase lead circuit.

[0131] The open-loop gain of the negative feedback loop is:

[0132] .

[0133] The transfer function of the capacitive sensing element is:

[0134] .

[0135] The phase-leading transfer function is:

[0136] (maximum phase) and gain = ).

[0137] The transfer function of a negative feedback loop has a peak response and a notch.

[0138] The notch frequency is the resonant frequency of a capacitive sensing element. .

[0139] The phase of the open-loop transfer function of a negative feedback loop without phase lead is approximately -180°, which may result in closed-loop instability.

[0140] The open-loop transfer function of a negative feedback loop with phase lead represents the positive phase margin at unity-gain frequency.

[0141] For reasonable values, the unity-gain frequency is approximately 30%-100% of the resonant frequency of the capacitive sensing element.

[0142] The phase lead frame should be designed to provide maximum phase lead over a range of 20% to 100% of the resonant frequency of the capacitive sensing element.

[0143] Figure 8 A Bode plot (800) representing the frequency response of the positive feedback loop is shown. An LPF (e.g., an LPF circuit) is needed to stabilize the positive feedback loop; and a preferred embodiment includes an LPF circuit in a unity-gain inverting amplifier because additional noise from the LPF circuit adds to V. n2 And by C sig Offset (e.g., when C)sig When the bias is a negative capacitor).

[0144] The positive feedback loop includes G2 and C. a Inverting amplifier, phase-leading, unity-gain inverting amplifier and LPF.

[0145] The open-loop gain of the positive feedback loop is:

[0146] .

[0147] The LPF transfer function is:

[0148] .

[0149] The open-loop transfer function of a positive feedback loop without an LPF has a gain >1 and a phase of approximately -180° at high frequencies, which may indicate closed-loop instability.

[0150] The open-loop transfer function of the positive feedback loop with LPF shows that the gain is <1 at high frequencies, which meets the stability requirements.

[0151] In some embodiments, a first-order or second-order LPF corner frequency can be selected to meet the gain margin requirements. For example, a typical value of the corner frequency will be in the range of approximately 4%-15% of the resonant frequency of the capacitive sensing element.

[0152] In some embodiments, in order to have a signal bandwidth of >20kHz, the resonant frequency of the capacitive sensing element is typically >200kHz.

[0153] Figures 9-10 A block diagram (900, 1000) of a portion of a microphone is shown, wherein the corresponding capacitive couplings (910, 920) of the negative feedback path and the positive feedback path to the microphone's electromechanical sensor (e.g., capacitive sensing element 112) are implemented as switching voltage dividers to facilitate modification of the microphone's circuit gain, for example, changing the microphone's sensitivity relative to detected changes in sound pressure.

[0154] In some embodiments, the first capacitive coupling of the negative feedback loop includes C g0 A first capacitive voltage divider is formed with the first switched capacitor (910). The second capacitive coupling of the positive feedback loop includes C a0 The second capacitive voltage divider is formed by the second switched capacitor (920). Conversely, the circuit gain of the electromechanical sensor can be modified by altering the corresponding small-signal capacitor gains of the first and second capacitive voltage dividers, while maintaining the defined load capacitance of the capacitive sensing element, for example, as described above, to reduce signal distortion. In some embodiments, such as... Figure 9 As shown, the switched capacitor is controlled by signal φ aand φ b To implement control. In this regard, when φ a When enabled, φ b Open / Disabled.

[0155] In some embodiments, the gain of the corresponding small-signal capacitors of the first and second capacitive voltage dividers can be modified by switching the respective capacitors of the first and second switched capacitors to ground. The gain of the switched capacitor 910 can be adjusted in G... 1a With G 1b Switching between them, while the gain of the switched capacitor 920 can be adjusted to G. 2a With G 2b Switching between them. This gain can be obtained by switching the corresponding capacitors of the first and second capacitive voltage dividers based on the following relationship:

[0156] When φa is enabled and φ b When disabled, the gain G a It equals the following values:

[0157]

[0158] ; as well as

[0159] When φ a Enable φ b When disabled, the gain G b It equals the following values:

[0160]

[0161] .

[0162] In some embodiments, the small signal gain / capacitor gain of 910 and the small signal gain / capacitor gain of 920 are not equal. In other embodiments, the small signal gain / capacitor gain of 910 and the small signal gain / capacitor gain of 920 are equal, i.e., G 1a =G 2a =G a and G 1b =G 2b =G b .

[0163] For example, if the sensitivity of the capacitive sensing element is At 94dB SPL, the following gains can be selected:

[0164] Output sensitivity, At 94db SPL,

[0165] Output sensitivity, At 94db SPL.

[0166] The relationship between the load capacitance of the capacitive sensing element and the gain A of the inverting amplifier is as follows:

[0167] .

[0168] The load capacitance depends on the gain A of the inverting amplifier 206, the small signal gain / capacitor gain (G1) of 910, and the small signal gain / capacitor gain (G2) of 920.

[0169] Therefore, in order to obtain an acceptable noise / distortion level for the microphone, the gain A of the inverting amplifier must be adjusted to keep AG approximately constant, for example, AG = 1.2, as shown below:

[0170]

[0171] .

[0172] When the voltage divider gain is G a At that time, the amplification gain A a Enabled; when the voltage divider gain is G b At that time, the amplification gain A b Enabled.

[0173] Figure 11 A block diagram (1100) of a portion of a microphone according to various exemplary embodiments is shown, wherein the electromechanical sensor of the microphone includes a single-ended output (“VOUT1”) corresponding to a negative feedback loop coupled to the electromechanical sensor via a V2V converter (1110) to facilitate modification of the microphone’s circuit gain, thereby altering the microphone’s sensitivity to detecting changes in sound pressure.

[0174] This part of the microphone includes an electromechanical sensor comprising a capacitive sensing element (112) having a first capacitive sensing element node and a second capacitive sensing element node. The V2V converter includes a V2V converter input “VIN” and a V2V output (“VOUT1”).

[0175] The V2V converter forms a negative feedback loop between its output and input. The negative feedback loop is electrically coupled to the node of the first capacitive sensing element via a capacitive coupling (214); the V2V converter output represents the sound pressure change detected by the capacitive sensing element.

[0176] In some embodiments, capacitive coupling includes a capacitive voltage divider, a resistive voltage divider, and / or an amplifier.

[0177] In other embodiments, the negative feedback loop alters the sensitivity of the V2V converter output to sound pressure changes via a capacitive voltage divider.

[0178] In another embodiment, the negative feedback loop modifies the sensitivity by altering the circuit gain of the electromechanical sensor.

[0179] In some embodiments, the microphone further includes a bias circuit (204) that applies a bias voltage (“V”) to the node of the first capacitive sensing element. b ”, where the bias voltage sets the operating node of the capacitive sensing element to the negative capacitance region.

[0180] The V2V converter includes an inverting amplifier (206) with a gain of -A and a phase-lead circuit (208). The V2V converter input is electrically coupled to the input of the inverting amplifier, and the negative feedback loop includes the inverting amplifier and the phase-lead circuit. In some embodiments, the inverting amplifier includes the phase-lead circuit.

[0181] In other embodiments, the circuit gain of the electromechanical sensor is modified by altering the gain of the small-signal capacitor in the capacitive voltage divider. In yet another embodiment, the small-signal capacitor gain is modified by switching the capacitor of the capacitive voltage divider to ground.

[0182] Figure 12 A block diagram (1200) of a portion of a microphone according to various exemplary embodiments is shown, wherein a positive feedback voltage and a negative feedback voltage are applied to the microphone's electromechanical sensor using a V2V converter (120), and wherein the nodes of the capacitive sensing element (112) of the electromechanical sensor are connected via a blocking capacitor ("C"). g It is electrically coupled to the V2V converter input to facilitate distortion reduction and improve the microphone's sensitivity to sound pressure changes.

[0183] The V2V converter includes a V2V converter input (“VIN”), a first V2V converter output (“VOUT1”), and a second V2V converter output (“VOUT2”). In some embodiments, the output of the electromechanical sensor includes the voltage difference between the first V2V converter output and the second V2V converter output, and represents the change in sound pressure detected by the capacitive sensing element.

[0184] The first bias circuit (202) is connected to the first bias resistor ("R"). a (For example, a high-impedance element (e.g., >1 GΩ)) applies a first bias voltage ("V") to the input of the V2V converter. a In some embodiments, V a It should be grounded (0 volts), or in a standard (e.g., CMOS) positive (e.g., "V") state.dd ) and negative (e.g., "V") ss "" is the reference voltage for the approximate midpoint voltage level between the power supply voltages.

[0185] The capacitive sensing element (112) includes a first capacitive sensing element node and a second capacitive sensing element node. A second bias circuit (204) (e.g., a charge pump) is connected via a second bias resistor (“R”). b A second bias voltage (“V”) is applied to the node of the second capacitive sensing element by a high-impedance element (e.g., >1 GΩ). b (For example, the voltage generated by the charge pump is much greater than the first bias voltage, for example, 5-50 volts), and the bias voltage sets the operating node of the capacitive sensing element to the negative capacitance region.

[0186] The V2V converter forms a negative feedback loop between the first V2V converter output and the V2V converter input; the negative feedback loop is electrically coupled to the first capacitive sensing element node through a gain stage (e.g., “G1”).

[0187] In some embodiments, the gain stage may include a capacitive voltage divider, a resistive voltage divider, and / or an amplifier.

[0188] The V2V converter forms a positive feedback loop between the output of the second V2V converter and the input of the V2V converter by means of an amplifier with a gain greater than 1 (e.g., an amplifier including an inverting amplifier and a unity-gain inverting amplifier), wherein the positive feedback loop is electrically coupled to the node of the second capacitive sensing element via a second capacitive coupling (216).

[0189] Furthermore, the second capacitive sensing element node is connected via a blocking capacitor ((C) g Electrically coupled to the input of the V2V converter.

[0190] Figure 13 A block diagram (1300) of a portion of another microphone according to various exemplary embodiments is shown, wherein a positive and negative feedback voltage is applied to the microphone's electromechanical sensor using a V2V converter (120), and wherein the node of the capacitive sensing element (112) of the electromechanical sensor is connected via a blocking capacitor ("C"). g "" is electrically coupled to the input of the V2V converter to facilitate distortion reduction and improve the microphone's sensitivity to sound pressure changes.

[0191] The V2V converter includes a V2V converter input (“VIN”), a first V2V converter output (“VOUT1”), and a second V2V converter output (“VOUT2”). In some embodiments, the output of the electromechanical sensor includes the voltage difference between the first V2V converter output and the second V2V converter output, and represents the change in sound pressure detected by the capacitive sensing element.

[0192] The first bias circuit (202) is connected to the first bias resistor ("R"). a (For example, a high-impedance element (e.g., >1 GΩ)) applies a first bias voltage ("V") to the input of the V2V converter. a In some embodiments, V a It is either grounded (0 volts) or in a standard (e.g., CMOS) positive (e.g., "V") state. dd ) and negative (e.g., "V") ss "" is the reference voltage for the approximate midpoint voltage level between the power supply voltages.

[0193] The capacitive sensing element (112) includes a first capacitive sensing element node and a second capacitive sensing element node. A second bias circuit (204) (e.g., a charge pump) is connected via a second bias resistor (“R”). b A second bias voltage (“V”) is applied to the node of the second capacitive sensing element by a high-impedance element (e.g., >1 GΩ). b (For example, the voltage generated by the charge pump is much greater than the first bias voltage, for example, 5-50 volts), and the bias voltage sets the operating node of the capacitive sensing element to the negative capacitance region.

[0194] The V2V converter forms a negative feedback loop between the output and input of the first V2V converter; and the negative feedback loop is electrically coupled to the node of the first capacitive sensing element.

[0195] The V2V converter forms a positive feedback loop between the output of the second V2V converter and the input of the V2V converter via an amplifier having a gain greater than 1 (e.g., the amplifier includes an inverting amplifier (206) and a unity-gain inverting amplifier (210)), wherein the positive feedback loop is electrically coupled to the node of the second capacitive sensing element via a capacitive coupling (216).

[0196] Furthermore, the second capacitive sensing element node is connected via a blocking capacitor (C). g Electrically coupled to the input of the V2V converter.

[0197] In some embodiments, the capacitive coupling 216 includes a capacitive voltage divider, a resistive voltage divider, and / or an amplifier.

[0198] In other embodiments, the positive feedback loop reduces signal distortion of the electromechanical sensor output, for example, by reducing the load capacitance electrically coupled to the capacitive sensing element.

[0199] In another embodiment, the positive feedback loop reduces the load capacitance by electrically coupling a negative capacitance to a capacitive sensing element.

[0200] Figure 14 A block diagram (1400) of a portion of a microphone according to various exemplary embodiments is shown, wherein the microphone’s electromechanical sensor includes a single-ended output (“VOUT1”) corresponding to a negative feedback loop coupled to the electromechanical sensor via a V2V converter (1410) to facilitate modification of the microphone’s circuit gain, thereby altering the microphone’s sensitivity to detecting changes in sound pressure.

[0201] The V2V converter includes a V2V converter input (“VIN”) and a V2V converter output (“VOUT1”). A first bias circuit (202) is connected via a first bias resistor (“R”). a (For example, a high-impedance element (e.g., >1 GΩ)) applies a first bias voltage ("V") to the input of the V2V converter. a In some embodiments, V a It should be grounded (0 volts), or in a standard (e.g., CMOS) positive (e.g., "V") state. dd ) and negative (e.g., "V") ss "" is the reference voltage for the approximate midpoint voltage level between the power supply voltages.

[0202] The capacitive sensing element (112) includes a first capacitive sensing element node and a second capacitive sensing element node. A second bias circuit (204) (e.g., a charge pump) is connected via a second bias resistor (“R”). b A second bias voltage (“V”) is applied to the node of the second capacitive sensing element by a high-impedance element (e.g., >1 GΩ). b (e.g., the voltage generated by the charge pump is much greater than the first bias voltage, for example, 5-50 volts), the bias voltage sets the operating node of the capacitive sensing element to the negative capacitance region.

[0203] The V2V converter forms a negative feedback loop between the output of the first V2V converter and the input of the V2V converter; the negative feedback loop is electrically coupled to the node of the first capacitive sensing element through a gain stage (e.g., "G").

[0204] In some embodiments, the gain stage may include a capacitive voltage divider, a resistive voltage divider, and / or an amplifier.

[0205] The second capacitive sensing element node passes through the blocking capacitor (C). gElectrically coupled to the V2V converter input and via a capacitor ("C") a ") Further electrical coupling to ground.

[0206] Figure 15 A block diagram (1500) of a portion of another microphone according to various exemplary embodiments is shown, wherein the microphone’s electromechanical sensor includes a single-ended output (“VOUT1”) corresponding to a negative feedback loop coupled to the electromechanical sensor via a V2V converter (1410) to facilitate modification of the microphone’s circuit gain, thereby altering the microphone’s sensitivity to detecting changes in sound pressure.

[0207] The V2V converter includes a V2V converter input (“VIN”) and a V2V converter output (“VOUT1”). A first bias circuit (202) is connected via a first bias resistor (“R”). a (For example, a high-impedance element (e.g., >1 GΩ)) applies a first bias voltage ("V") to the input of the V2V converter. a In some embodiments, V a It is either grounded (0 volts) or in a standard (e.g., CMOS) positive (e.g., "V") state. dd ) and negative (e.g., "V") ss "" is the reference voltage for the approximate midpoint voltage level between the power supply voltages.

[0208] The capacitive sensing element (112) includes a first capacitive sensing element node and a second capacitive sensing element node. A second bias circuit (204) (e.g., a charge pump) is connected via a second bias resistor (“R”). b A second bias voltage (“V”) is applied to the node of the second capacitive sensing element by a high-impedance element (e.g., >1 GΩ). b (For example, the voltage generated by the charge pump is much greater than the first bias voltage, for example, 5-50 volts), and the bias voltage sets the operating node of the capacitive sensing element to the negative capacitance region.

[0209] The V2V converter forms a negative feedback loop between the output and input of the first V2V converter; and the negative feedback loop is electrically coupled to the node of the first capacitive sensing element.

[0210] The second capacitive sensing element node passes through the blocking capacitor (C). g Electrically coupled to the V2V converter input and through a capacitor ("C") a ") Further electrical coupling to ground.

[0211] In some embodiments, since the feedback gain is equal to 1, VOUT1 = V sig .

[0212] Figure 16 A block diagram of a portion of a microphone according to various exemplary embodiments is shown, wherein a positive feedback voltage and a negative feedback voltage are applied to the microphone’s electromechanical sensor using a V2V converter, wherein the node of the capacitive sensing element of the electromechanical sensor and the negative feedback loop are electrically coupled to the input of the V2V converter to facilitate the reduction of distortion and the improvement of the microphone’s sensitivity to the detection of sound pressure changes, and wherein a phase lead circuit is included in the negative feedback loop.

[0213] In this regard, for circuit stability, the gain of the phase-leading circuit (phase-leading 208) increases the gain of the high-frequency response of the negative feedback loop, while LPF 212 decreases the gain of the low-frequency response of the positive feedback loop. Therefore, it is advantageous not to have a phase-leading circuit in the positive feedback loop. In the signal band of the electromechanical sensor, the gain of 210 should be equal to and opposite to the gain of the phase-leading circuit (phase-leading 208) to provide differential output, such as VOUT1 – VOUT2.

[0214] Throughout this specification, the terms "an embodiment" or "an embodiment" refer to a specific feature, structure, or characteristic associated with that embodiment, which is included in at least one implementation. Therefore, the phrases "in one embodiment" or "in one implementation" appearing in various places throughout this specification do not necessarily refer to the same embodiment. Furthermore, in one or more embodiments, specific features, structures, or characteristics may be combined in any suitable manner.

[0215] Furthermore, where terms such as “comprising,” “having,” “including,” and other similar words are used in the detailed specification or appended claims, these terms are intended to be inclusive in a manner similar to the word “comprising” as an open transition, without excluding any additional or other elements. Additionally, the word “or” is intended to mean an inclusive “or,” not an exclusive “or.” That is, unless otherwise stated or the context clearly indicates, “X uses A or B” is intended to mean any natural inclusive arrangement. That is, if X uses A; X uses B; or X uses both A and B, then in any of the above cases, “X uses A or B” holds true. Furthermore, the articles “a” and “an” used in this application and the appended claims should generally be interpreted as “one or more,” unless otherwise stated or clearly indicated from the context as singular.

[0216] Furthermore, the terms “exemplary” and / or “illustrator” as used herein mean as an example, instance, or illustration. For the avoidance of doubt, the subject matter disclosed herein is not limited to these examples. Moreover, any aspect or design described herein as “exemplary” and / or “illustrator” is not necessarily to be construed as superior to other aspects or designs, nor does it exclude equivalent exemplary structures and techniques known to those skilled in the art that have the benefits of this disclosure.

[0217] The above description of the embodiments shown in this invention is not intended to be exhaustive or to limit the disclosed embodiments to the precise forms disclosed. While specific embodiments and examples have been described herein for illustrative purposes, those skilled in the art will recognize that various modifications can be made within the scope of these embodiments and examples.

[0218] In this regard, while the disclosed subject matter has been described in conjunction with various embodiments and corresponding drawings, it will be understood, where applicable, that other similar embodiments may be used, or modifications and additions may be made to the described embodiments to perform the same, similar, alternative, or substitutive functions of the disclosed subject matter without departing from it. Therefore, the disclosed subject matter should not be limited to any single embodiment described herein, but should be interpreted broadly and comprehensively in accordance with the appended claims.

Claims

1. A microphone, comprising: An electromechanical sensor includes a capacitive sensing element, which includes a first capacitive sensing element node and a second capacitive sensing element node. as well as A voltage-to-voltage converter includes a voltage-to-voltage converter input, a first voltage-to-voltage converter output, and a second voltage-to-voltage converter output. A second capacitive sensing element node is electrically coupled to the voltage-to-voltage converter input. The voltage-to-voltage converter forms a negative feedback loop between the first voltage-to-voltage converter output and the voltage-to-voltage converter input. This negative feedback loop is electrically coupled to the first capacitive sensing element node via a first capacitive coupling. The voltage-to-voltage converter forms a positive feedback loop between the second voltage-to-voltage converter output and the voltage-to-voltage converter input via an amplifier with a gain greater than 1. This positive feedback loop is electrically coupled to the second capacitive sensing element node via a second capacitive coupling.

2. The microphone as claimed in claim 1, wherein, At least one of the first capacitive coupling or the second capacitive coupling includes at least one of the following: Capacitive voltage divider; Resistive voltage divider; or Amplifier.

3. The microphone as claimed in claim 1, wherein, The output of the electromechanical sensor includes the voltage difference between the output of the first voltage-to-voltage converter and the output of the second voltage-to-voltage converter, and the output represents the sound pressure change detected by the capacitive sensing element.

4. The microphone as claimed in claim 3, wherein, The positive feedback loop reduces the load capacitance electrically coupled to the capacitive sensing element.

5. The microphone as claimed in claim 4, wherein, The positive feedback loop reduces distortion by electrically coupling a negative capacitor to the capacitive sensing element.

6. The microphone as claimed in claim 1, wherein, The negative feedback loop includes a voltage divider, and wherein, The negative feedback loop modifies the sensitivity of the electromechanical sensor output to the detection of sound pressure changes detected by the capacitive sensing element via the voltage divider. The output of the electromechanical sensor includes the voltage difference between the output of the first voltage-to-voltage converter and the output of the second voltage-to-voltage converter.

7. The microphone as claimed in claim 6, wherein, The negative feedback loop modifies the sensitivity by adjusting the circuit gain of the electromechanical sensor.

8. The microphone as claimed in claim 3, wherein, The first capacitive coupling includes a first capacitive voltage divider, wherein the second capacitive coupling includes a second capacitive voltage divider, and wherein the circuit gain of the electromechanical sensor is modified by modifying the corresponding small-signal capacitor gains of the first and second capacitive voltage dividers.

9. The microphone as claimed in claim 8, wherein, The gain of the corresponding small-signal capacitor is modified by switching the corresponding capacitors of the first and second capacitive voltage dividers to ground.

10. The microphone of claim 1, further comprising a bias circuit that applies a bias voltage to the first capacitive sensing element node, wherein, The bias voltage sets the operating node of the capacitive sensing element to the negative capacitance region.

11. The microphone as claimed in claim 1, wherein, The voltage-to-voltage converter includes an inverting amplifier and a phase-leading circuit, wherein the input of the voltage-to-voltage converter is electrically coupled to the inverting amplifier input of the inverting amplifier, and wherein the negative feedback loop includes the inverting amplifier and the phase-leading circuit.

12. The microphone of claim 11, wherein, The inverting amplifier includes the phase-leading circuit.

13. The microphone of claim 11, wherein, The voltage-to-voltage converter includes a unity-gain inverting amplifier and a low-pass filter, wherein the positive feedback loop includes the unity-gain inverting amplifier and the low-pass filter.

14. The microphone of claim 13, wherein, The circuit output corresponding to this phase-leading circuit is electrically coupled to the circuit input corresponding to this unity-gain inverting amplifier.

15. The microphone of claim 13, wherein, The unity-gain inverting amplifier includes this low-pass filter.

16. The microphone as claimed in claim 1, wherein, A bias voltage is applied to the second capacitive sensing element node via a bias resistor, wherein the second capacitive sensing element node is electrically coupled to the voltage-to-voltage converter input via a blocking capacitor.

17. A microphone, comprising: An electromechanical sensor includes a capacitive sensing element, which includes a first capacitive sensing element node and a second capacitive sensing element node. as well as A voltage-to-voltage converter includes a voltage-to-voltage converter input and a voltage-to-voltage converter output, wherein the second capacitive sensing element node is electrically coupled to the voltage-to-voltage converter input. The voltage-to-voltage converter forms a negative feedback loop between its output and input. This negative feedback loop is electrically coupled to the node of the first capacitive sensing element via capacitive coupling. The output of the voltage-to-voltage converter represents the sound pressure change detected by the capacitive sensing element.

18. The microphone of claim 17, wherein, The capacitive coupling includes at least one of the following: Capacitive voltage divider; Resistive voltage divider; or Amplifier.

19. The microphone of claim 17, wherein, The negative feedback loop includes a voltage divider, and wherein, The negative feedback loop modifies the sensitivity of the voltage-to-voltage converter output to detecting changes in sound pressure via the voltage divider.

20. The microphone of claim 19, wherein, The negative feedback loop modifies the sensitivity by adjusting the circuit gain of the electromechanical sensor.

21. The microphone of claim 20, further comprising a bias circuit that applies a bias voltage to the first capacitive sensing element node, wherein, The bias voltage sets the operating node of the capacitive sensing element to the negative capacitance region.

22. The microphone of claim 17, wherein, The voltage-to-voltage converter includes an inverting amplifier and a phase-leading circuit, wherein the input of the voltage-to-voltage converter is electrically coupled to the inverting amplifier input of the inverting amplifier, and wherein the negative feedback loop includes the inverting amplifier and the phase-leading circuit.

23. The microphone of claim 22, wherein, The inverting amplifier includes the phase-leading circuit.

24. The microphone of claim 18, wherein, The circuit gain of the electromechanical sensor is modified by changing the gain of the small-signal capacitor of the capacitive voltage divider.

25. The microphone of claim 24, wherein, The gain of the small signal capacitor is modified by switching the capacitor of the capacitive voltage divider to ground.

26. The microphone of claim 17, wherein, A bias voltage is applied to the second capacitive sensing element node via a bias resistor, wherein the voltage is electrically coupled to the voltage converter input via a blocking capacitor to the second capacitive sensing element node.

27. A microphone, comprising: An electromechanical sensor includes a capacitive detection element, wherein the capacitive detection element includes a first capacitive detection element node and a second capacitive detection element node. as well as A voltage-to-voltage converter includes a voltage-to-voltage converter input and a voltage-to-voltage converter output, wherein a second capacitive sensing element node is electrically coupled to the voltage-to-voltage converter input, wherein the voltage-to-voltage converter forms a negative feedback loop between the voltage-to-voltage converter output and the voltage-to-voltage converter input, and wherein the negative feedback loop is electrically coupled to the first capacitive sensing element node; and The voltage-to-voltage converter output represents the sound pressure change detected by the capacitive sensing element.

28. The microphone of claim 27, wherein, The voltage-to-voltage converter includes an inverting amplifier and a phase-lead circuit, wherein the input of the voltage-to-voltage converter is electrically coupled to the inverting amplifier input of the inverting amplifier, and wherein the negative feedback loop includes the inverting amplifier and the phase-lead circuit.

29. The microphone of claim 28, wherein, The inverting amplifier includes the phase-leading circuit.

30. The microphone of claim 27, wherein, A bias voltage is applied to the second capacitive sensing element node via a bias resistor, wherein the voltage is electrically coupled to the voltage converter input via a blocking capacitor to the second capacitive sensing element node.

31. A microphone, comprising: An electromechanical sensor includes a capacitive sensing element, which includes a first capacitive sensing element node and a second capacitive sensing element node. A bias resistor that electrically couples the bias voltage to the node of the second capacitive sensing element; as well as A voltage-to-voltage converter includes a voltage-to-voltage converter input, a first voltage-to-voltage converter output, and a second voltage-to-voltage converter output. A second capacitive sensing element node is electrically coupled to the voltage-to-voltage converter input via a blocking capacitor. The voltage-to-voltage converter forms a negative feedback loop between the first voltage-to-voltage converter output and the voltage-to-voltage converter input. This negative feedback loop is electrically coupled to the first capacitive sensing element node. The voltage-to-voltage converter forms a positive feedback loop between the second voltage-to-voltage converter output and the voltage-to-voltage converter input via an amplifier with a gain greater than 1. This positive feedback loop is electrically coupled to the second capacitive sensing element node via capacitive coupling.

32. The microphone of claim 31, wherein, The capacitive coupling includes at least one of the following: Capacitive voltage divider, Resistive voltage divider; or Amplifier.

33. The microphone as claimed in claim 31, wherein, The output of the electromechanical sensor includes the voltage difference between the output of the first voltage-to-voltage converter and the output of the second voltage-to-voltage converter, and the output represents the sound pressure change detected by the capacitive sensing element.

34. The microphone as claimed in claim 33, wherein, The positive feedback loop reduces the load capacitance of the output of the electromechanical sensor.

35. The microphone as claimed in claim 34, wherein, The positive feedback loop reduces signal distortion by electrically coupling a negative capacitor to the capacitive sensing element.

36. The microphone of claim 31, wherein, The voltage-to-voltage converter includes an inverting amplifier and a phase-leading circuit, wherein the input of the voltage-to-voltage converter is electrically coupled to the inverting amplifier input of the inverting amplifier, and wherein the negative feedback loop includes the inverting amplifier and the phase-leading circuit.

37. The microphone of claim 36, wherein, The inverting amplifier includes the phase-leading circuit.

38. The microphone of claim 36, wherein, The voltage-to-voltage converter includes a unity-gain inverting amplifier and a low-pass filter, wherein the circuit output corresponding to the phase-leading circuit is electrically coupled to the circuit input corresponding to the unity-gain inverting amplifier, and wherein the positive feedback loop includes the unity-gain inverting amplifier and the low-pass filter.

39. The microphone of claim 38, wherein, The circuit output corresponding to this phase-leading circuit is electrically coupled to the circuit input corresponding to this unity-gain inverting amplifier.

40. The microphone of claim 38, wherein, The unity-gain inverting amplifier includes this low-pass filter.

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