CN103067819B - microphone amplifying circuit - Google Patents
microphone amplifying circuit Download PDFInfo
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- CN103067819B CN103067819B CN201110317016.1A CN201110317016A CN103067819B CN 103067819 B CN103067819 B CN 103067819B CN 201110317016 A CN201110317016 A CN 201110317016A CN 103067819 B CN103067819 B CN 103067819B
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Abstract
The invention provides a kind of microphone amplifying circuit, comprise PNP transistor (Q1) and NPN transistor (Q2), wherein, the emitter of PNP transistor (Q1) is connected with the collector electrode of NPN transistor (Q2) by the first resistor (R7); The collector electrode of PNP transistor (Q1) is connected with the base stage of NPN transistor (Q2); And the collector electrode of NPN transistor (Q2) externally exports the signal after amplifying by the second resistor (R9), wherein, the resistance value of the first resistor (R7) and the second resistor (R9) is provided so that PNP transistor (Q1) carries out low power amplification, and makes described first resistor, the second resistor and PNP transistor form negative-feedback circuit relative to NPN transistor.This amplifying circuit carries out profound and negative feedbck by the gain of sacrificing front stage transistor circuit, utilizes the non-linear of rear class transistor circuit to ensure output stability and the linearity.
Description
Technical field
The present invention relates to amplifying circuit, more specifically, relate to a kind of low noise high dynamic range microphone amplifying circuit that can ensure output stability and the linearity.
Background technology
In the microphone amplifying circuit of single power supply, due to the existence of DC offset voltage, generally can there is DC level when static state and export.And in the microphone amplifying circuit provided at present, most of amplifying circuit adopts resistor negative feedback network.Fig. 1 shows the basic structure of general negative feedback amplifier circuit.As shown in Figure 1, feedback network F is realized by resistor network.For this feedback network, open-loop gain is A=x
o/ x
id, feedback factor is F=x
f/ x
o, closed loop gain is A
f=AF, depth of feedback is 1+AF, and profound and negative feedbck condition is 1+AF > > 1, wherein x
othe output of amplifying circuit, x
iinput signal, and x
idit is the input signal after superposing with feedback signal.What adopt due to general amplifying circuit is resistor feedback network, and feedback factor is certain, cannot dynamic adjustments feedback factor, thus can not accomplish gain stabilization when causing audio signal to change within the scope of audio frequency full frequency band.
In addition, the direct ground connection of the emitter due to output stage transistor, thus be difficult to the level of Static output level equalization to demand.For this reason, general amplifying circuit needs to adjust for Static output level.Common Static output level adjustable strategies is by emitter resistors in series.But there is contradiction when meeting high-gain and demand Static output level in this implementation, namely cannot meet the requirements of Static output level when resistor is little, and can reduce multiplication factor when resistor is large, be i.e. the gain of amplifying circuit.In addition, also can adopt general-purpose operation amplifier to realize, but adopt the cost of general-purpose operation amplifier relatively high, simultaneously in the amplifying circuit of band bias voltage, very difficult realization can provide the power supply required for the multiplication factor of high-gain, it is stable not that this causes exporting quiescent voltage, needs thus again to adjust quiescent voltage, and again adjust and can increase a lot of cost.
Summary of the invention
In view of the above problems, the invention provides a kind of microphone amplifying circuit, there is the transistor circuit of two cascades, wherein front stage transistor circuit is used as the negative-feedback circuit of rear class transistor circuit, carry out profound and negative feedbck by the gain of sacrificing front stage transistor circuit, utilize the non-linear of rear class transistor circuit to ensure output stability and the linearity.
According to an aspect of the present invention, provide a kind of microphone amplifying circuit, comprise PNP transistor and NPN transistor, wherein, the emitter of described PNP transistor is connected with the collector electrode of described NPN transistor by the first resistor; The collector electrode of described PNP transistor is connected with the base stage of described NPN transistor; And the collector electrode of described NPN transistor externally exports the signal after amplification by the second resistor, wherein, the resistance value of described first resistor and the second resistor is provided so that described PNP transistor carries out low power amplification, and makes described first resistor, the second resistor and described PNP transistor form negative-feedback circuit relative to described NPN transistor.
In addition, in one or more embodiment of the present invention, described microphone amplifying circuit also can also comprise the first capacitor with described first capacitor in parallel.
In addition, in one or more embodiment of the present invention, described microphone amplifying circuit can also comprise: be arranged on the 3rd resistor of connecting successively between the emitter of described PNP transistor and base stage and the 4th resistor; And the 5th resistor be arranged between the base stage of described PNP transistor and earth terminal.
In addition, in one or more embodiment of the present invention, described microphone amplifying circuit can also comprise the 3rd resistor of connecting successively between emitter and the non-ground output of described microphone and the 6th resistor that are arranged on described PNP transistor.
In addition, in one or more embodiment of the present invention, described microphone amplifying circuit can also comprise the second capacitor between junction and earth terminal being arranged on described 3rd resistor and the 6th resistor.
In addition, in one or more embodiment of the present invention, described microphone amplifying circuit can also comprise: be arranged on the 3rd capacitor of connecting successively between the base stage of described PNP transistor and the non-ground output of microphone and the 4th capacitor; The 5th capacitor between the output being arranged on described microphone; And the 7th resistor be arranged between the junction of described 3rd capacitor and the 4th capacitor and described earth terminal.
In addition, in one or more embodiment of the present invention, described microphone amplifying circuit can also comprise at least one capacitor be arranged between one end be not connected with the collector electrode of described NPN transistor in described second resistor and described earth terminal.
In addition, in one or more embodiment of the present invention, described microphone amplifying circuit can also comprise the 8th resistor parallel with one another between collector electrode and described earth terminal and the 6th capacitor that are arranged on described PNP transistor.
In addition, in one or more embodiment of the present invention, described microphone amplifying circuit can also comprise forward and be arranged at least one diode between the emitter of described NPN transistor and earth terminal.
In addition, in one or more embodiment of the present invention, described microphone amplifying circuit can also comprise the 9th resistor between emitter and earth terminal being arranged on described NPN transistor.
In order to realize above-mentioned and relevant object, will describe in detail and the feature particularly pointed out in the claims after one or more aspect of the present invention comprises.Explanation below and accompanying drawing describe some illustrative aspects of the present invention in detail.But what these aspects indicated is only some modes that can use in the various modes of principle of the present invention.In addition, the present invention is intended to comprise all these aspects and their equivalent.
Accompanying drawing explanation
According to following detailed description of carrying out with reference to accompanying drawing, above and other object of the present invention, feature and advantage will become more apparent.In the accompanying drawings:
Fig. 1 shows the schematic diagram of amplifying circuit of the prior art;
Fig. 2 shows the structural representation of the amplifying circuit according to the first embodiment of the present invention;
The small-signal model that Fig. 3 A and 3B respectively illustrates NPN transistor and PNP transistor simplifies circuit;
Fig. 4 shows the equivalent circuit diagram of the amplifying circuit shown in Fig. 2;
Fig. 5 shows the structural representation of amplifying circuit according to a second embodiment of the present invention;
Fig. 6 shows the equivalent circuit diagram of the amplifying circuit shown in Fig. 5; With
Fig. 7 shows the circuit application example schematic diagram according to amplifying circuit of the present invention.
Label identical in all of the figs indicates similar or corresponding feature or function.
Embodiment
Each embodiment of the present invention is described below with reference to accompanying drawings.
(the first embodiment)
Fig. 2 shows the structural representation of the amplifying circuit 10 according to the first embodiment of the present invention.
See Fig. 2, described amplifying circuit 10 comprises the transistor of two cascades, that is, PNP transistor Q1 and NPN transistor Q2.
As shown in Figure 2, the emitter of PNP transistor Q1 by resistor R7 (namely, first resistor) and capacitor C1 is (namely, first capacitor) be connected to the collector electrode of NPN transistor Q2, this resistor R7 and capacitor C1 is connected in parallel between the emitter of PNP transistor Q1 and the collector electrode of NPN transistor Q2.In another example of the present invention, also can omit capacitor C1 when noise required precision is low.
The collector electrode of NPN transistor Q2 by resistor R9 (namely, second resistor) signal after amplifying circuit 10 amplifies is outputted to late-class circuit or outside, and the other end be not connected with the collector electrode of NPN transistor Q2 in resistor R9 and between earth terminal, two capacitor C6 and C7 can also be arranged in parallel, and output to outside or late-class circuit after the process through capacitor C6 and C7.In other example of the present invention, according to design needs, above-mentioned capacitor C6 and C7 can only arrange one, or, above-mentioned capacitor C6 and C7 can be omitted.The emitter of NPN transistor Q2 is connected to earth terminal by resistor R10 (that is, the 9th resistor).
Resistor R5 (that is, the 3rd resistor) and the resistor R3 (that is, the 4th resistor) of series connection is mutually provided with between the emitter and base stage of PNP transistor Q1.In addition, between the base stage and earth terminal of PNP transistor Q1, be provided with resistor R4 (that is, the 5th resistor).Resistor R5, R3 and R4 carry out dividing potential drop, to the base stage of PNP transistor Q1 and emitter-base bandgap grading bias voltage, thus form the biasing circuit of PNP transistor Q1.In addition, preferably, between the base stage and earth terminal of PNP transistor Q1, the capacitor C8 that carry out filtering in parallel with resistor R4 can also be provided with.
In addition, as shown in Figure 2, resistor R1 (that is, the 6th resistor) can also be provided with between the junction of resistor R5 and R3 and the non-ground output of microphone.When carrying out direct current supply, the power supply of whole DC circuit is inputted by J1, and direct voltage is inputted by first pin of J1, by resistor R9, and R7, R5, and resistor R1 is to microphone direct current biasing, thus form the biasing circuit of microphone.
Here be noted that in other embodiments of the invention, also can omit above-mentioned biasing circuit, or adopt the biasing circuit be made up of other circuit element.Being known in the art about how forming biasing circuit, not being described in detail at this.
In addition, as shown in Figure 2, can also capacitor C5 (that is, the second capacitor) be set between the junction of resistor R1 and resistor R5 and earth terminal.Utilize this capacitor C5, can prevent the AC signal owing to coming from resistor R1 branch road from entering into the emitter of PNP transistor Q1 and the offset change that causes and the signal skew that causes and export unstable.In addition, by arranging resistor R5 and capacitor C5, can also ensure that rear class feedback signal cannot seal in prime, thus reduce noise, improve signal quality.
In addition, as shown in Figure 2, resistor R6 parallel with one another can also be set between the collector electrode of PNP transistor Q1 and earth terminal (namely, 8th resistor) and capacitor C9 is (namely, 6th capacitor), signal for exporting the collector electrode of PNP transistor Q1 carries out filtering, thus improves the quality of output signals of PNP transistor Q1.
In addition, filter circuit unit can also be comprised between the base stage and the output of microphone of PNP transistor Q1.As shown in Figure 2, (namely described filter circuit unit comprises capacitor C2 (that is, the 5th electric capacity), capacitor C3 (that is, the 3rd capacitor), capacitor C4,4th capacitor) and resistor R2 (that is, the 7th resistor).Filter unit forms a higher order filter, carries out filtering for Mic signal, to reduce signal noise.Described capacitor C3 and C4 is arranged between the non-ground output of microphone and the base stage of PNP transistor Q1, described capacitor C2 is arranged between microphone ground non-ground output and ground, and between the described resistor R2 junction that is arranged on described capacitor C3 and C4 and earth terminal.Equally, filter circuit unit described herein is also only example, and filter circuit unit also can adopt other suitable configuration.In addition, in other embodiments of the invention, above-mentioned filter circuit unit can be omitted equally.
Fig. 3 A and 3B respectively illustrates the small-signal model simplified electrical circuit diagram of NPN transistor and PNP transistor, and Fig. 4 shows the equivalent circuit diagram of the amplifying circuit shown in Fig. 2.Referring to the equivalent circuit diagram shown in Fig. 4, the course of work of the amplifying circuit shown in Fig. 2 is described.
When amplifying circuit 10 operates, microphone Mic collected sound signal, and gathered voice signal is transformed into AC signal.Described AC signal carries out filtering by capacitor C2 in parallel, then capacitor C3 is connected to, then after capacitor C3, resistors in parallel R2 forms a filter circuit, then series capacitor C4, is directly entered into the base stage of PNP transistor Q1 by capacitor C4.
Enter into the base stage of PNP transistor Q1 (as first order amplifying circuit) of microphone amplifying circuit 10 at input signal after, export from collector electrode after PNP transistor Q1 amplifies.Signal after exporting from the collector electrode of PNP transistor Q1, through the filtering process of R6 and C9 in parallel, then enters into the base stage of NPN transistor Q2, as the input signal of NPN transistor Q2, to improve the input signal quality of Q2.
NPN transistor Q2 is as second level amplifying circuit, the signal of the base stage entering NPN transistor Q2 is amplified, AC signal after amplification exports from the collector electrode of NPN transistor Q2, and by resistor R9, and capacitor C6, C7 output to outside or late-class circuit.Meanwhile, the signal exported from the collector electrode of NPN transistor Q2 feeds back to PNP transistor Q1 by resistor R7, forms negative feedback loop.
PNP transistor Q1 processes feedback signal, and by arranging resistor R7 and R9, make the signal feeding back to PNP transistor Q1 not be very large, the signal fed back enters the base stage of Q1, is input to the base stage of Q2 via Q1 collector electrode again.By arranging PNP transistor Q1, the mode of sacrificing Q1 gain can be adopted, make to feed back very little signal reaches profound and negative feedbck effect through the effect of Q1, thus regulate the output of Q2, improve the output linearity degree of Q2, improve the stability of the output of NPN transistor Q2.
In addition, owing to being connected on the existence of the resistance R10 of the emitter of Q2, the DC level that Q2 exports has been raised, so the scope of output level can be arranged by the resistance value arranging resistor R10 further.
Compared to other resistive degeneration circuit, owing to there is PNP transistor Q1 this grade of amplifying circuit, as long as cause the output of NPN transistor Q2 to separate a very little part to feed back to PNP crystal Q1, just good feedback effects can be reached.In addition, the computing formula according to the negative feedback network in Fig. 1 can be found out, under same feedback condition, the amplifying circuit of the present embodiment can adjust by PNP transistor Q1 the adjustment that the signal feedbacked carries out depth of feedback, thus realizes high-gain.And if common resistive degeneration circuit wants to improve depth of feedback, must feed back more signal, this directly can cause the reduction of output gain.
As can be seen from the above, according in the amplifying circuit of the present embodiment, by the resistance value of described first resistor R7 and the second resistor R9 is arranged so that described PNP transistor Q1 carries out low power amplification, and described first resistor R7, the second resistor R9 and described PNP transistor Q1 is made to form negative-feedback circuit relative to described NPN transistor Q2.In this manner, front stage transistor circuit is used as the negative-feedback circuit of rear class transistor circuit, thus degree of depth feedback can be carried out by the gain of sacrificing front stage transistor circuit, and the non-linear of transistor circuit is utilized to ensure output stability and the linearity.
In addition, by being arranged on the capacitor C5 between the junction of resistor R1 and R5 and earth terminal, can prevent the AC signal owing to coming from resistor R1 branch road from entering into the emitter of PNP transistor Q1 and the offset change that causes and the signal skew that causes and export unstable.When input signal is voice signal, the capacitance of usual capacitor C5 is preferably set between 100uF ~ 220uF.In addition, by arranging resistor R5 and capacitor C5, can also ensure that rear class feedback signal cannot seal in prime, thus reduce noise, improve signal quality.
With reference to Fig. 2 to Fig. 4, amplifying circuit 10 is according to a first embodiment of the present invention illustrated above, but should be appreciated that, above-described embodiment is only exemplary, and those skilled in the art when not deviating from scope of the present invention, can also carry out various amendment to above-described embodiment.In other embodiments, also can delete the subelement shown in above-described embodiment or circuit, or the element in above-described embodiment is reconfigured.Such as, delete above-mentioned biasing circuit and/or filter circuit unit, or the formation of above-mentioned biasing circuit and/or filter circuit unit is modified.In addition, also can arrange according to specific design parameter according to the parameter value of each element of the microphone amplifying circuit of above-described embodiment.
(the second embodiment)
Fig. 5 shows the structural representation of amplifying circuit 20 according to a second embodiment of the present invention.Most of composed component in amplifying circuit 20 shown in Fig. 5 is identical with the amplifying circuit 10 shown in Fig. 2, and amplifying circuit 20 is only to utilize two diodes D1, D2 to replace resistor R10 with the difference of the amplifying circuit 10 shown in Fig. 2.As shown in Figure 5, two diodes are in series arranged between the emitter of NPN transistor Q2 and earth terminal by forward.Particularly, the positive pole of diode D1 is connected with the emitter of NPN transistor Q2, and the negative pole of diode D1 is connected with the positive pole of diode D2, and the negative pole of diode D2 is connected with earth terminal.According to design needs, in another example of the present invention, between the emitter and earth terminal of NPN transistor Q2, also only a diode can be set forward, or forward arrange mutually series connection more than two diodes.
Fig. 6 shows the equivalent circuit diagram of the amplifying circuit 20 shown in Fig. 5.The operation principle of amplifying circuit 20 is substantially identical with the amplifying circuit 10 shown in Fig. 2.Only difference is described below.
Owing to being provided with diode D1, D2 of forward series connection at the emitter of NPN transistor Q2 and earth terminal, the diode D1 of this forward series connection, output DC level has been raised in the existence of D2, thus can reach rear class and require level.In addition, when input exchange signal is very large, and when output is amplified to very high peak value, diode D1, D2, by entering the control of the level magnitude of saturated cut-off region to NPN transistor Q2, can control the amplitude exchanging output level.
As can be seen from the above, compared with the mode by realizing in emitting stage series resistance with general amplifying circuit for the adjustable strategies of output stage level, according to the amplifying circuit of the present embodiment, the Static output level that rear class requires can be realized while meeting high-gain.That is, in this manner, the following problems existed in original adjustable strategies can be overcome: output DC level cannot be met the requirements of when resistance is little, and multiplication factor can be reduced when resistance is large.
Fig. 7 shows the circuit application example schematic diagram according to amplifying circuit 10/20 of the present invention.As shown in Figure 7, be amplification circuits of the present invention in the square frame of the left side, Line A and Line B distinguishes 1 pin and 2 pin of J1 in corresponding diagram 2.
Amplifying circuit according to the present invention is particularly suitable for being applied in microphone, amplifies for the AC signal exported microphone.In addition, other signal output apparatus is also suitable for according to amplifying circuit of the present invention.
Revise according to embodiments of the invention above with reference to accompanying drawing, but it is clear that need not perform with any particular order according to the function of the claim to a method of the embodiments described herein, step and/or action.In addition, although element of the present invention can, with individual formal description or requirement, also it is contemplated that multiple, be odd number unless explicitly limited.
Although describe each embodiment according to the present invention above with reference to figure to be described, it will be appreciated by those skilled in the art that each embodiment that the invention described above is proposed, various improvement can also be made on the basis not departing from content of the present invention.Therefore, protection scope of the present invention should be determined by the content of appending claims.
Claims (9)
1. a microphone amplifying circuit, comprises PNP transistor (Q1) and NPN transistor (Q2), wherein,
The emitter of described PNP transistor (Q1) is connected with the collector electrode of described NPN transistor (Q2) by the first resistor (R7);
The collector electrode of described PNP transistor (Q1) is connected with the base stage of described NPN transistor (Q2); And
The collector electrode of described NPN transistor (Q2) externally exports the signal after amplifying by the second resistor (R9),
Wherein, the resistance value of described first resistor (R7) and the second resistor (R9) is provided so that described PNP transistor (Q1) carries out low power amplification, and makes described first resistor (R7), the second resistor (R9) and described PNP transistor (Q1) form negative-feedback circuit relative to described NPN transistor (Q2);
Wherein, also comprise: be arranged on the 3rd resistor (R5) of connecting successively between the emitter of described PNP transistor (Q1) and base stage and the 4th resistor (R3); And the 5th resistor (R4) be arranged between the base stage of described PNP transistor (Q1) and earth terminal and the filtering capacitor (C8) in parallel with described 5th resistor (R4).
2. microphone amplifying circuit as claimed in claim 1, also comprises:
First capacitor (C1) in parallel with described first resistor (R7).
3. microphone amplifying circuit as claimed in claim 1, also comprises:
Be arranged on the 6th resistor (R1) of connecting with described 3rd resistor (R5) between the emitter of described PNP transistor (Q1) and the non-ground output of described microphone.
4. microphone amplifying circuit as claimed in claim 3, also comprises:
Be arranged on the second capacitor (C5) between the junction of described 3rd resistor (R5) and the 6th resistor (R1) and earth terminal.
5. microphone amplifying circuit as claimed in claim 1, also comprises:
Be arranged on the 3rd capacitor (C3) of connecting successively between the base stage of described PNP transistor (Q1) and the non-ground output of microphone and the 4th capacitor (C4);
The 5th capacitor (C2) between the output being arranged on described microphone; And
Be arranged on the 7th resistor (R2) between the junction of described 3rd capacitor (C3) and the 4th capacitor (C4) and described earth terminal.
6. microphone amplifying circuit as claimed in claim 1, also comprises:
Be arranged at least one capacitor (C6) between one end be not connected with the collector electrode of described NPN transistor (Q2) in described second resistor (R9) and described earth terminal.
7. microphone amplifying circuit as claimed in claim 1, also comprises:
Be arranged on the 8th resistor (R6) in parallel successively between the collector electrode of described PNP transistor (Q1) and described earth terminal and the 6th capacitor (C9).
8., as the microphone amplifying circuit in claim 1 to 7 as described in any one, also comprise:
Forward is arranged at least one diode (D1) between the emitter of described NPN transistor (Q2) and earth terminal.
9., as the microphone amplifying circuit in claim 1 to 7 as described in any one, also comprise:
Be arranged on the 9th resistor (R10) between the emitter of described NPN transistor (Q2) and earth terminal.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201110317016.1A CN103067819B (en) | 2011-10-18 | 2011-10-18 | microphone amplifying circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201110317016.1A CN103067819B (en) | 2011-10-18 | 2011-10-18 | microphone amplifying circuit |
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| Publication Number | Publication Date |
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| CN103067819A CN103067819A (en) | 2013-04-24 |
| CN103067819B true CN103067819B (en) | 2015-09-30 |
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Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3124759A (en) * | 1964-03-10 | Two stage transistor amplifier with | ||
| US4044297A (en) * | 1975-05-20 | 1977-08-23 | Matsushita Electric Industrial Co., Ltd. | Ultrasonic generator with combined oscillator and current regulator |
| US4214215A (en) * | 1978-08-02 | 1980-07-22 | Contact Communication Corporation | Low noise-high gain JFET amplifier for a piezoelectric transducer |
| JPS60157309A (en) * | 1984-01-27 | 1985-08-17 | Toshiba Corp | Amplifier circuit device |
| CN87210280U (en) * | 1987-07-16 | 1988-05-18 | 宋克明 | Piezoelectric telephone transmitting amplifier |
| JPH02231983A (en) * | 1989-03-02 | 1990-09-13 | Rohm Co Ltd | Driving circuit for dc motor |
| CN101675669A (en) * | 2007-02-16 | 2010-03-17 | Rfsemi科技有限公司 | microphone amplifier |
| CN101729028A (en) * | 2008-10-24 | 2010-06-09 | 三洋电机株式会社 | Amplifier device |
| CN202310064U (en) * | 2011-10-18 | 2012-07-04 | 歌尔声学股份有限公司 | Microphone amplifying circuit |
-
2011
- 2011-10-18 CN CN201110317016.1A patent/CN103067819B/en active Active
Patent Citations (9)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3124759A (en) * | 1964-03-10 | Two stage transistor amplifier with | ||
| US4044297A (en) * | 1975-05-20 | 1977-08-23 | Matsushita Electric Industrial Co., Ltd. | Ultrasonic generator with combined oscillator and current regulator |
| US4214215A (en) * | 1978-08-02 | 1980-07-22 | Contact Communication Corporation | Low noise-high gain JFET amplifier for a piezoelectric transducer |
| JPS60157309A (en) * | 1984-01-27 | 1985-08-17 | Toshiba Corp | Amplifier circuit device |
| CN87210280U (en) * | 1987-07-16 | 1988-05-18 | 宋克明 | Piezoelectric telephone transmitting amplifier |
| JPH02231983A (en) * | 1989-03-02 | 1990-09-13 | Rohm Co Ltd | Driving circuit for dc motor |
| CN101675669A (en) * | 2007-02-16 | 2010-03-17 | Rfsemi科技有限公司 | microphone amplifier |
| CN101729028A (en) * | 2008-10-24 | 2010-06-09 | 三洋电机株式会社 | Amplifier device |
| CN202310064U (en) * | 2011-10-18 | 2012-07-04 | 歌尔声学股份有限公司 | Microphone amplifying circuit |
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| CN103067819A (en) | 2013-04-24 |
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Address after: 261031 Dongfang Road, Weifang high tech Industrial Development Zone, Shandong, China, No. 268 Patentee after: Goertek Inc. Address before: 261031 Dongfang Road, Weifang high tech Industrial Development Zone, Shandong, China, No. 268 Patentee before: Goertek Inc. |
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Effective date of registration: 20200731 Address after: 266104 room 103, 396 Songling Road, Laoshan District, Qingdao, Shandong Province Patentee after: Goer Microelectronics Co.,Ltd. Address before: No.268, Dongfang Road, high tech Industrial Development Zone, Weifang City, Shandong Province Patentee before: GOERTEK Inc. |