CN103997303B - For the high-gain preamplifier and electret microphone of electret microphone - Google Patents
For the high-gain preamplifier and electret microphone of electret microphone Download PDFInfo
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- CN103997303B CN103997303B CN201410201152.8A CN201410201152A CN103997303B CN 103997303 B CN103997303 B CN 103997303B CN 201410201152 A CN201410201152 A CN 201410201152A CN 103997303 B CN103997303 B CN 103997303B
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- nmos
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- nmos pass
- electret microphone
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Abstract
The present invention discloses a kind of electret microphone high-gain preamplifier.The amplifier includes PMOS transistor, the first and second nmos pass transistors, and current source, wherein the grid of PMOS transistor is used as the input of the amplifier, the output end of the drain electrode as the amplifier of second nmos pass transistor, the first end of the current source is connected with the drain electrode of the second nmos pass transistor, second end is connected with the drain electrode of the source electrode and the first nmos pass transistor of the PMOS transistor, the grid connection of first and second nmos pass transistor, and the source ground of the drain electrode of the PMOS transistor and the first and second nmos pass transistors.Thus the present invention provides the preamplifier that a kind of high-gain, small volume can be applied to ECM microphones.The present invention also provides a kind of electret microphone including the preamplifier.
Description
Technical field
The present invention relates to microelectronics technology, more properly, belongs to CMOS integrated circuits, the circuit is used as communication system
The preamplifier of middle electret (ECM) microphone.
Background technology
In speech communication system, mainly still realize voice signal to telecommunications using electret (ECM) microphone at present
Number conversion.Electret (ECM) microphone is two pin devices, and one of pin ground connection, another pin are used for signal
Export and to chip power supply.ECM microphones composition includes 3 parts：Microphone case, electret capacitor and preamplifier.
There are electret capacitor microphone head, junction field effect transistor (JFET) amplifier in microphone case.This employing JFET amplifies
The features such as two pin ECM microphones of device are easy to application and low manufacture cost with which is used widely in communication system.
However, with the reduction of portable type electronic product volume, electret capacitor microphone head volume progressively reduces, microphone case diameter
30mm is reduced to via 90mm, electret capacitor is reduced to 2.0-2.5pF or so by about 10pF.And the input of JFET device
Capacitance size is typically in the 10pF orders of magnitude, if still amplified using junction field effect transistor (JFET) in electret microphone
Device, it will weaken the sensitivity of electret microphone, causes its signal to noise ratio (SNR) to be deteriorated.Accordingly, it would be desirable to high-gain, low input
The preamplifier device of electric capacity is substituting traditional JFET amplifiers.
United States Patent (USP) US6888408B2 proposes a kind of high-gain preamplifier manufactured with CMOS technology, such as Fig. 1 institutes
Show, this amplifier pin is consistent with JFET device pin, can be used directly to substitute JFET amplifiers.This amplifier is used
Used as input, nmos device drains as amplifier out pmos source follower, and including two-stage amplifying circuit, first
Level circuit includes pmos source follower, and voltage amplification factor is less than or is close to 1, and second level circuit includes the two of common source configuration
Individual nmos device, voltage gain can be made very high.The grid of PMOS device PM1 is used as the input of amplifier, its source electrode
Output is coupled to second circuit by capacitor C1.In the circuit of the second level, to provide direct current for nmos device NM1 inclined for nmos device NM2
Pressure.Whole amplifier gain is mainly determined by second level circuit that its output voltage gain can be with approximate evaluation as NM2 mutual conductance Gm2
With the product of load resistance RL, i.e.,：Gm2*RL.In order to obtain high voltage gain, the size of nmos device NM2 will be made compared with
Greatly to obtain high mutual conductance Gm2, in order to not reduce device from first order amplifier to the gain loss of second level amplifier, coupling
Close capacitor C1 to also be made it is larger affected with reducing its partial pressure, so whole chip size also will become big therewith.
This amplifier mainly has following shortcoming：
1) integrated large capacitor C1 is needed in amplifier, it will take very large chip area；
2) amplifier needs the resistor R1 of integrated big resistance, but the resistance of the resistor is hardly resulted in manufacturing process
Precise control, namely the voltage gain of amplifier hardly results in precise control；
3) resistor R1 and capacitor C1 define high-pass filtering circuit, and such circuit structure is difficult while meet should
Filter circuit low end frequency is sought less than 50Hz, obtains rapidly nmos device NM1 when requiring electricity on amplifier stable straight
The requirement of stream bias.
Additionally, United States Patent (USP) US6160450 proposes another kind of high-gain preamplifier manufactured with BiCMOS technologies,
As shown in Figure 2.The pin of this amplifier is consistent with JFET device pin, can be used directly to substitute JFET amplifiers.It is this
, used as differential amplifier inputs, bipolar device NPN transistor Qout is used as output end for amplifier PMOS transistor M1 and M2.
This amplifier is mainly characterized by PMOS transistor M1 and M2 of input difference amplifier and adopts dissymmetrical structure, transistor M1
Source series resistor Roffset, the grid of transistor M2 can be biased in higher than M1 grid voltages, the grid of transistor M1
It is grounded by diode Dbias, because not having electric current to pass through, the voltage of the grid is about zero volt, and such transistor M2 grids can
Bias with by feedback voltage on output end resistance Rgain, due to input PMOS amplifiers and the multiplication factor of amplifier B
It is very high, PMOS amplifiers, the backfeed loop of amplifier B and bipolar device Qout compositions so that the voltage on resistor Rgain
Vgain follows voltage change on input electret capacitor, and on load Rload, curent change follows electric current on resistor Rgain
Change, such amplifier voltage gain are Rload/Rgain.The resistance size for reconciling resistor Rgain can obtain different electricity
Pressure gain.The advantage of this circuit is that voltage gain can adjust control very well, but has following points not enough：
1) PMOS difference amplifiers and internal amplifier B increased the noise of chip；
2) PMOS difference amplifiers Miller effects cause input capacitance to become big；
3) using MOS device and bipolar device (BJT), improve manufacturing cost.
4) presence of resistor Roffset also increases chip noise.
Accordingly, it would be desirable to a kind of high-gain, small volume, are preferably able to be applied to the preamplifier of ECM microphones.
The content of the invention
Exist for existing electret (ECM) microphone Conventional amplifiers JFET and two kinds of amplifiers noted earlier
Deficiency, the invention is intended to propose a kind of new high-gain preamplifier, is stayed to small-sized with meeting in present voice-communication device
The high-gain of polar body amplifier, the requirement of small size.
According to an aspect of the present invention, there is provided a kind of electret microphone high-gain preamplifier, the amplifier
It is made up of two-stage amplifying circuit, used as input, electricity is amplified in the second level to wherein first order amplifying circuit pmos source follower
Road is to use NMOS commonsource amplifiers, and first order amplifying circuit to second level amplifying circuit is realized with mirror current source.
According to a further aspect in the invention, there is provided a kind of electret microphone high-gain preamplifier, the amplifier
Including a PMOS transistor, the first and second nmos pass transistors, and current source,
The grid of the PMOS transistor is used as the input of the amplifier, and the drain electrode of second nmos pass transistor is used as
The output end of the amplifier,
The first end of the current source is connected with the drain electrode of the second nmos pass transistor, the second end and the PMOS transistor
The drain electrode connection of source electrode and the first nmos pass transistor,
The grid connection of first and second nmos pass transistor, and
The drain electrode of the PMOS transistor and the source ground of the first and second nmos pass transistors.
Preferably, the grid of PMOS transistor is grounded by resistive device.For example, the grid can by resistor,
The resistive device such as diode or MOS device is grounded.
Preferably, the current source is realized with first resistor device.
Preferably, the current source is realized with depletion type nmos transistor and second resistance device.
Preferably, first end of the drain electrode of the depletion type nmos transistor as the current source, the depletion type
The source series of nmos pass transistor are connected the second end as the current source with its grid after connecting the second resistance device.
Preferably, the current source is realized in the way of two PMOS transistors and reference current source.
Preferably, the source electrode of first and second nmos pass transistor passes through resistor respectively or resistive device is grounded.
Preferably, the preamplifier further includes the low pass being coupling between the grid of the first and second nmos devices
Wave filter.
In accordance with a further aspect of the present invention, there is provided a kind of electret microphone, including electret microphone as above
Use high-gain preamplifier.
Preamplifier of the invention, when the input voltage of input PMOS transistor changes, due to first
The clamping action that the structure of the diode of nmos device has so that the source voltage of PMOS transistor can be kept substantially
It is constant, maintain the threshold voltage value (Vth) of the first nmos device up and down.Due to current source current it is constant, so, with flowing through
The change of PMOS transistor current, the electric current for flowing through the first nmos pass transistor accordingly increased or decrease identical quantity therewith.The
One and second nmos pass transistor constitute mirror current source, the electric current of the second nmos pass transistor follows the first nmos pass transistor in proportion
Curent change and change.When the value of channel width-over-length ratio W/L of the second nmos pass transistor is the raceway groove width of the first nmos pass transistor
When growing N times than the value of W/L, the electric current of the second nmos pass transistor is also N times of the first NMOS transistor current.Thus, before this
The voltage gain Gv for putting amplifier can be derived as：
Gv=Gpm1*N*RL
Wherein Gpm1 is the mutual conductance of PMOS device, and N is the channel width-over-length ratio and a NMOS crystal of the second nmos pass transistor
The ratio of the channel width-over-length ratio of pipe, RL are output end load resistances.By design current ource electric current and PMOS transistor size come
The mutual conductance Gpm1 of setting PMOS device, and dimensional ratios N of the first and second nmos pass transistors are set, preposition amplification can be obtained
High-gain required for device.
The preamplifier that the present invention is provided can be manufactured using CMOS ic manufacturing technologies, than the integrated electricity of BiCMOS
Road manufacturing technology low cost., using PMOS transistor as amplifier in, grid can be for example, by high resistance for the present invention
Value resistor ground connection, can so realize the preamplifier of low noise and low input capacitance.The preposition amplification of the present invention
The output par, c of device can further realize its high-gain using the common source configuration of the first and second nmos pass transistors.Meanwhile,
From first order amplifying circuit to second level amplifying circuit, the first and second nmos pass transistors constitute image current source structure, input
The 2nd NMOS of output end device is arrived in the curent change reflection identical with the curent change of PMOS transistor of the first nmos pass transistor of level
Transistor, this avoid low frequency capacitive coupled problem of the amplifier first order to the second level in United States Patent (USP) US6888408B2.
Further, according to a preferred embodiment of the invention, by the shape between the current source of the first and second nmos devices composition mirror image
Noise signal of the audio frequency in more than 20KHz can be filtered into low pass filter, circuit output signal to noise ratio (SNR) is improved.When
When the low pass filter is realized in the form of resistor and capacitor, by by the size design of resistor and capacitor in reasonable model
In enclosing, the low pass filter is easily integrated on chip.
Description of the drawings
Below in conjunction with the accompanying drawings the specific embodiment of the present invention is described in further detail.
Fig. 1 illustrates the ECM preamplifier circuit schematic diagrames of one of prior art.
Fig. 2 illustrates the ECM preamplifier circuit schematic diagrames of another prior art.
Fig. 3 illustrates the ECM CMOS preamplifier circuit schematic diagrames according to first preferred embodiment of the invention.
Fig. 4 illustrates the ECM CMOS preamplifier circuit schematic diagrames according to second preferred embodiment of the invention.
Fig. 5 illustrates the typical gains distribution of preamplifier shown in Fig. 4.
Fig. 6 illustrates ECM CMOS preamplifier circuit schematic diagrames according to a third embodiment of the present invention.
Fig. 7 illustrates ECM CMOS preamplifier circuit schematic diagrames according to a fourth embodiment of the present invention.
Fig. 8 illustrates ECM CMOS preamplifier circuit schematic diagrames according to a fourth embodiment of the present invention.
Fig. 9 illustrates ECM CMOS preamplifier circuit schematic diagrames according to a fourth embodiment of the present invention.
Specific embodiment
In order to be illustrated more clearly that the utility model, the utility model is done into one with reference to preferred embodiments and drawings
The explanation of step.In accompanying drawing, similar part is indicated with same or analogous reference.Those skilled in the art should manage
Solution, below specifically described content be illustrative and be not restrictive, protection model of the present utility model should not be limited with this
Enclose.
Fig. 3 illustrates the circuit diagram of the CMOS preamplifiers 300 of ECM according to a first embodiment of the present invention.It is preposition
Amplifier 300 includes PMOS transistor PM1 as the first order, used as the first and second NMOS that the common source of the second level connects
Transistor NM1, NM2 and current source.The grid of PMOS transistor PM1 is used as the input of preamplifier, with electret mike
The ECM transducers coupling of wind, the drain electrode of the second nmos pass transistor NM2 are used as the output end of preamplifier 300.Supply voltage
VDD Jing output ends provide power for the preamplifier 300 by load resistance RL.Supply voltage Jing current sources I1 distinguishes coupling
It is bonded to grid and the drain electrode of the source electrode and the first nmos pass transistor NM1 of PMOS transistor PM1.The first and second NMOS crystal
The grid connection of pipe, also, the drain electrode of PMOS transistor PM1, the first and second nmos pass transistor NM1, the source ground of NM2.
First order PMOS transistor can be configured to pmos source follower, and its gate input is grounded by high resistance device Rb, with reality
Existing low noise and low input capacitance, and DC easy to set up biass.As replacement, the grid of PMOS transistor can by diode,
MOS device or other circuit structures for being equal to resistor are realized.
When the voltage change of input PMOS device PM1 input, due to the diode-type structure institute of nmos device NM1
The clamping action having so that PMOS device PM1 source voltage is held essentially constant, maintains nmos device NM1 threshold voltages
Value (Vth) is up and down.Due to current source I1 current constants, with decreasing or increasing for PMOS transistor PM1 electric current is flowed through, flow through
The electric current of nmos pass transistor NM1 accordingly increaseds or decreases identical quantity therewith.First and second nmos pass transistor NM1 and NM2
Mirror current source is constituted, transistor NM2 electric currents follow transistor NM1 curent changes in proportion.If the raceway groove of nmos pass transistor NM2
Breadth length ratio W/L value is N times of the channel width-over-length ratio W/L value of transistor NM1, and transistor NM2 curent changes will be then transistor NM1
N times of device current.
When the microphone electret voltage being connected with input is due to sound pressure variations, cause the input voltage of preamplifier
During change, the electric current for flowing through transistor PM1 also changes, and such as increases Δ I, then the electric current for flowing through transistor NM1 is corresponding
Reduce Δ I, transistor NM2 electric currents also reduce Δ I*N therewith, and the output end voltage change of amplifier is turned to
Δ V=Δ I*N*RL,
The voltage gain Gv of preamplifier is：
Gv=Δ I*N*RL/ Δ V=Gpm1*N*RL.
Wherein, Gpm1=Δs I/ Δ V, are the mutual conductances of PMOS device PM1, therefore, the gain of preamplifier is by PMOS devices
The mutual conductance of part PM1 and nmos device NM2 are determined to dimension scale N of NM1.
The mutual conductance Gpm1 of PM1 is set by design current ource electric current I1 and PMOS device PM1 size, and by setting
Device size ratios N of the NM2 to NM1, can obtain the voltage gain required for preamplifier.By this way, PMOS is brilliant
The size of body pipe PM1 is without very greatly, input capacitance is controlled within 2pF, just can increase the gain of amplifier.
Using pmos source follower as input, PMOS grids can be biased in zero volt to amplifier of the present invention, output
End is nmos transistor drain, and pin is consistent with JFET amplifiers, can directly replace JFET amplifiers to be used in electret (ECM)
On microphone.Microphone is also two pin devices, and one of pin ground connection, another pin are used for signal output and to core
Piece is powered.ECM microphones can be used on mobile phone and other voice transfer electronic products.
Fig. 4 illustrates the circuit diagram of the CMOS preamplifiers 400 of ECM according to a second embodiment of the present invention.It is different
In the preamplifier 300 shown in Fig. 3, the preamplifier 400 further includes to be connected to the first and second nmos pass transistors
First resistor device R1 and the first capacitor C1 being connected between first resistor device and ground potential between the grid of NM1, NM2.
In the preamplifier 400, the grid of first order PMOS transistor PM1 is as input and by a big resistance
Resistor Rb ground connection.The drain and gate of PMOS transistor PM1 source electrode and the first nmos pass transistor NM1 is connected to current source I1,
Nmos pass transistor NM1 is diode structure, flow through its curent change it is little when, drain-gate pole tension is basically unchanged, and maintains NMOS
Transistor NM1 threshold voltage values (Vth) is up and down.So, when input terminal voltage changes, PMOS transistor PM1 source voltage base
This holding is constant, the gate-source voltage Vgs of PMOS transistor PM1 changes, and PMOS transistor is changed by electric current.
Due to current source I1 current constants, thus when PMOS transistor by electric current when decreasing or increasing, flow through nmos pass transistor
The electric current of NM1 increaseds or decreases identical quantity therewith on the contrary.Nmos device NM2 and NM1 constitute mirror current source, in order to reduce
Device 1/f noise, nmos pass transistor NM1 and NM2 are all large-size devices, while designing breadth length ratio W/L of nmos pass transistor NM2
Value is N times of the breadth length ratio W/L value of NM1 devices, and the electric current that such transistor NM2 passes through is Ns of the transistor NM1 by electric current
Times.Preferably, between transistor NM1 and NM2, form resistor R1 and capacitor C1 and constitute low pass filter, can filter
Noise signal of the audio frequency in more than 20KHz, improves the signal to noise ratio (SNR) of preamplifier 400.In the embodiment, position
It is large-size device in the nmos pass transistor NM2 of output end, chip current major part flows through transistor NM2.As replacement, connection
RC low pass filters between transistor NM1 and NM2 can also be realized with circuit structure.
Preamplifier of the invention 400, from first order PMOS amplifier to second level NMOS amplifiers, circuit is adopted
Use image current source structure, circuit internal signal transmission to adopt current signal, rather than voltage signal, on the one hand solve output
The DC-bias problem of end transistor NM2, this avoid in existing United States Patent (USP) US6888408B2 the amplifier first order to
Two grades of Capacitance Coupled problem, on the other hand causes the integrated low pass filter between nmos device NM1 and NM2 to be possibly realized.
By increasing low pass filter, noise signal of the audio frequency in more than 20KHz can be filtered, thus improve circuit output noise
Than (SNR).Simultaneously by resistor R1 and capacitor C1 sizes are designed in the reasonable scope, can be easily integrated by them
To on chip.Fig. 5 shows the typical gains distribution of preamplifier 400, it can be seen that 20KHz above section signals are low by RC
Bandpass filter is suppressed.
It is preferred that, the embodiment can be used alone and can also be used in combination with other embodiment.
Fig. 6 illustrates the circuit diagram of the CMOS preamplifiers 600 of ECM according to a third embodiment of the present invention.At this
In embodiment, current source is realized in the way of resistor R2, and other parts are identical with second embodiment shown in Fig. 4.By by electricity
Resistance device is used as current source, can simplify the circuit structure of preamplifier, obtain high-gain, small size with simple circuit structure
ECM microphone preamplifiers.
It is preferred that, the embodiment can be used alone and can also be used in combination with other embodiment.
Fig. 7 illustrates the circuit diagram of the CMOS preamplifiers 700 of ECM according to a fourth embodiment of the present invention.At this
In embodiment, current source is realized with depletion type nmos transistor NM3, and other parts are identical with second embodiment shown in Fig. 4.It is preferred that
Ground, current source are realized with depletion type nmos transistor NM3 and resistor R2.The drain electrode of depletion type nmos transistor NM3 is used as electricity
The one end in stream source is connected with the drain electrode of the second nmos pass transistor, its grid and source electrode connection after as current source the other end and institute
State PMOS transistor source electrode and the first nmos pass transistor drain electrode connection, resistor R2 be connected to transistor NM3 source electrode and
Between the other end.Resistor R2 plays negative feedback, make current source output electric current it is more stable, output current is with electricity
Source voltage is varied less.
It is preferred that, the embodiment can be used alone and can also be used in combination with other embodiment.
Fig. 8 illustrates the circuit diagram of the CMOS preamplifiers 800 of ECM according to a fifth embodiment of the present invention.At this
In embodiment, current source can also realize with PMOS transistor that other parts are identical with second embodiment shown in Fig. 4.. preferably
Ground, the current source include second and the 3rd PMOS transistor PM2 and PM3 and reference current source Iref.
It is preferred that, the embodiment can be used alone and can also use with reference to other embodiment.
It should be appreciated by those skilled in the art that the implementation method of current source also has multiple choices, can be with connected applications at this
In the preamplifier of invention.
Fig. 9 illustrates the circuit diagram of the CMOS preamplifiers 900 of ECM according to a sixth embodiment of the present invention.At this
In embodiment, in the source that the first and second nmos pass transistor NM1 and NM2 constitute image current, nmos pass transistor NM1 and NM2
Source electrode difference resistors in series Rs1 and Rs2.So, the electric current for flowing through nmos pass transistor NM1 and NM2 can be more symmetrical.Simultaneously
The source voltage that PMOS transistor PM1 can be adjusted or the electric current for flowing through PM1, so as to adjust the gain of PMOS transistor PM1.
It is preferred that, the embodiment can be used alone and can also be used in combination with other embodiment.
For save space and reduces cost, first order transistor and second level transistor are preferably integrated on chip and are formed
Integrated circuit lead.The preamplifier for being formed as integrated circuit lead is suitable for application in various applications very limited amount of in space
In environment, particularly apply in electret ECM microphones.
Obviously, the above embodiment of the present invention is only intended to clearly illustrate example of the present invention, and is not right
The restriction of embodiments of the present invention, for those of ordinary skill in the field, may be used also on the basis of the above description
To make other changes in different forms, all of embodiment cannot be exhaustive here, it is every to belong to this
Bright technical scheme it is extended obvious change or change still in protection scope of the present invention row.
Claims (10)
1. a kind of electret microphone high-gain preamplifier, the amplifier are made up of two-stage circuit, and wherein the first order is put
Big circuit adopts pmos source follower, using the grid of PMOS transistor as the input of amplifier, second level amplifying circuit
Using the NMOS commonsource amplifiers of two nmos pass transistors, the source electrode of PMOS transistor is connected to the grid of the first nmos device
And drain electrode, the output end of the drain electrode of the second nmos device as amplifier, first order amplifying circuit to second level amplifying circuit are used
Mirror current source is realizing.
2. a kind of electret microphone high-gain preamplifier, the amplifier include PMOS transistor, first and second
Nmos pass transistor, and current source,
Characterized in that,
The grid of the PMOS transistor is used as the input of the amplifier, and the drain electrode of second nmos pass transistor is put as this
The output end of big device,
The first end of the current source is connected with the drain electrode of the second nmos pass transistor, the source electrode of the second end and the PMOS transistor
Drain electrode with the first nmos pass transistor connects,
The drain electrode of first nmos pass transistor and the grid of the first nmos pass transistor connect,
The grid connection of first and second nmos pass transistor, and
The drain electrode of the PMOS transistor and the source ground of the first and second nmos pass transistors.
3. electret microphone as claimed in claim 1 or 2 high-gain preamplifier, it is characterised in that PMOS crystal
The grid of pipe passes through resistor or resistive device is grounded.
4. electret microphone as claimed in claim 1 or 2 high-gain preamplifier, it is characterised in that the electric current
Realized with first resistor device in source.
5. electret microphone as claimed in claim 1 or 2 high-gain preamplifier, it is characterised in that the electric current
Realized with depletion type nmos transistor and second resistance device in source.
6. electret microphone as claimed in claim 5 high-gain preamplifier, it is characterised in that the depletion type
First end of the drain electrode of nmos pass transistor as the current source, the source series connection of the depletion type nmos transistor are described
It is connected the second end as the current source after second resistance device with its grid.
7. electret microphone as claimed in claim 1 or 2 high-gain preamplifier, it is characterised in that the electric current
Realized in the way of two PMOS transistors and reference current source in source.
8. electret microphone as claimed in claim 2 high-gain preamplifier, it is characterised in that described first and
The source electrode of bi-NMOS transistor passes through resistor respectively or resistive device is grounded.
9. electret microphone as claimed in claim 2 high-gain preamplifier, it is characterised in that the preamplifier
Further include the low pass filter being coupling between the grid of the first and second nmos devices.
10. a kind of preposition amplification of high-gain of electret microphone, including electret microphone as claimed in claim 1 or 2
Device.
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| CN201410201152.8A CN103997303B (en) | 2014-05-13 | 2014-05-13 | For the high-gain preamplifier and electret microphone of electret microphone |
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| CN201410201152.8A CN103997303B (en) | 2014-05-13 | 2014-05-13 | For the high-gain preamplifier and electret microphone of electret microphone |
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| CN103997303B true CN103997303B (en) | 2017-04-05 |
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| CN109347312A (en) * | 2018-11-30 | 2019-02-15 | 常州拓晶照明科技有限公司 | A kind of electric source filter circuit integrated |
| CN111431487A (en) * | 2020-04-14 | 2020-07-17 | 四川聚阳科技集团有限公司 | Low-noise microphone preamplifier circuit |
| CN113342120A (en) * | 2021-06-25 | 2021-09-03 | 上海料聚微电子有限公司 | PTAT voltage generating circuit and band-gap reference circuit |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| US5325069A (en) * | 1992-12-29 | 1994-06-28 | Exar Corporation | CMOS opamp with large sinking and sourcing currents and high slew rate |
| US6888408B2 (en) * | 2002-08-27 | 2005-05-03 | Sonion Tech A/S | Preamplifier for two terminal electret condenser microphones |
| US7332965B2 (en) * | 2006-04-19 | 2008-02-19 | Texas Instruments Incorporated | Gate leakage insensitive current mirror circuit |
| CN102645950B (en) * | 2011-02-22 | 2013-12-25 | 安凯(广州)微电子技术有限公司 | Buffer applied to low-dropout regulator |
| CN203942499U (en) * | 2014-05-13 | 2014-11-12 | 北京燕东微电子有限公司 | For high-gain preamplifier and the electret microphone of electret microphone |
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