CN103107782A - High-gain front-arranged amplifier for electret electrochemical machining (ECM) microphone - Google Patents
High-gain front-arranged amplifier for electret electrochemical machining (ECM) microphone Download PDFInfo
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- CN103107782A CN103107782A CN2011103622027A CN201110362202A CN103107782A CN 103107782 A CN103107782 A CN 103107782A CN 2011103622027 A CN2011103622027 A CN 2011103622027A CN 201110362202 A CN201110362202 A CN 201110362202A CN 103107782 A CN103107782 A CN 103107782A
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Abstract
The invention discloses a high-gain front-arranged amplifier for an electret electrochemical machining (ECM) microphone used in a communication system. A P-channel metal oxide semiconductor (PMOS) source electrode follower is adopted to be used as an input end, the size of a PMOS M3 does not need to be big, and input capacitance can be controlled in 2pF, so that high gain of the amplifier can be increased. A PdOS source electrode follower is adopted to be used as an input end, an input end of an amplifier A is easily arranged to be direct current (DC) bias voltage, complementary metal-oxide-semiconductor transistor (CMOS) integrated circuit manufacturing technology is adopted, and manufacturing cost is reduced.
Description
Technical field
The present invention relates to a kind of CMOS integrated circuit, refer specifically to a kind of electret for communication system (ECM) microphone high-gain preamplifier.
Background technology
Speech communication system mainly still realizes that with electret (ECM) microphone voice signal is to the transformation of the signal of telecommunication now.The ECM microphone is two pin devices, mainly comprises the electret capacitor microphone head, nodal pattern field-effect transistor (JFET) amplifier.ECM microphone the two poles of the earth device of this employing JFET is used widely at communication system owing to the characteristics such as being easy to use and cost of manufacture is low.Yet along with reducing of portable type electronic product volume, electret capacitor microphone head volume progressively reduces, and electric capacity is reduced to the 2.0-2.5pF left and right by about 10pF.And the input capacitance of JFET device has weakened the sensitivity of electret microphone in the 10pF magnitude, causes ECM microphone signal to noise ratio (SNR) variation.Therefore, need high-gain, low input capacitance device substitutes JFET.
United States Patent (USP) 6160450 has proposed a kind of both-end high-gain preamplifier with the manufacturing of BiCMOS technology, sees Fig. 2, substitutes JFET.As input, bipolar NPN device is as output with the PMOS differential amplifier for this amplifier.The shortcoming of this amplifier has following points, 1) differential amplifier increases the chip noise as input; 2) differential amplifier Miller effect causes that input capacitance is large; 3) adopt MOS and BJT device manufacturing technology cost high; 4) circuit produces the DC bias voltage with Roffset, and the asymmetric while Roffset of differential amplifier increases the chip noise
Summary of the invention
The present invention proposes to reduce the chip manufacturing cost in order to solve the problem that exists in above technology, improve gain, make bias current be easy to the preamplifier of regulating and reducing noise.
The present invention adopts the pmos source follower as input, and as shown in Figure 1, PMOS M3 size need not be very large, and input capacitance can be controlled in 2pF, just can increase amplifier gain.Adopt the pmos source follower as input, amplifier A input is easy to arrange the DC bias voltage.In addition, the present invention adopts the CMOS ic manufacturing technology, reduces manufacturing cost.
Detailed circuit of the present invention as shown in Figure 3, chip current has been controlled PMOS M3 direct grid current bias voltage (VG_M3) mainly by nmos device M1, has just controlled chip current.Under the effect of differential amplifier A, PMOS M2 grid voltage VG_M2 and PMOS_M3 grid voltage VG_M3 equate, by the electric current I M1=VG_M2/R2=VG_M3/R2 of M1, PMOS M3 grid voltage VG_M3 can regulate by R4, therefore can regulate chip current.
As shown in Figure 3, amplifier gain of the present invention is R1/R2, and R1 is generally fixed value 2.2K Ω in application, therefore by regulating R2, just adjustable gain.Such as, select R2=1K Ω, amplifier gain is 6.8dB; Face adopts traditional JFET gain to be generally less than 0dB.Chip current and operating current can be controlled by regulating R4, and therefore, gain and electric current can be controlled respectively by regulating R2 and R4 respectively.As shown in Figure 4 and Figure 5, R3 is high resistant, is the DC biasing resistor, and the input of C1 composition high communication number, and C1 can be adjusted to the 5pF left and right.The R3 size should satisfy frequency will have the flat rubber belting input higher than the 50Hz signal, is suppressed lower than 50Hz.The chip frequency response is low so all can be very smooth to 50Hz.Adopt simultaneously AC coupling input, there is not the DC biasing problem in input.In addition, high resistant R3 also can be in accurate transoid bias state realization with diode (Diode) or PMOS.
Description of drawings
The present invention is further illustrated below in conjunction with accompanying drawing.
Fig. 1 is amplifier schematic equivalent circuit of the present invention.
Fig. 2 is the preamplifier circuit contrast figure of United States Patent (USP) 6160450 inventions.
Fig. 3 is the preamplifier circuit schematic diagram that the present invention adopts the CMOS technology.
Fig. 4 is that the present invention utilizes diode to realize the amplifier circuit schematic diagram of DC biasing
Fig. 5 is that the present invention utilizes PMOS to realize the amplifier circuit schematic diagram of DC biasing
Embodiment
As shown in Figure 1, the present invention adopts the pmos source follower as input, and PMOS M3 size need not be very large, and input capacitance can be controlled in 2pF, just can increase amplifier gain.Adopt the pmos source follower as input, amplifier A input is easy to arrange the DC bias voltage.In addition, the present invention adopts the CMOS ic manufacturing technology, reduces manufacturing cost.
As shown in Figure 3, chip current mainly by nmos device M1, has been controlled PMOS M3 direct grid current bias voltage (VG_M3), has just controlled chip current.Due to the effect of differential amplifier A, PMOS M2 grid voltage VG_M2 and PMOS M3 grid voltage VG_M3 equate.Electric current I M1=VG_M2/R2=VG_M3/R2 by M1.PMOS M3 grid voltage VG_M3 can be regulated by R4, therefore chip current can be regulated.
As shown in Figure 3, amplifier gain of the present invention is R1/R2.In application, R1 is generally 2.2K Ω, regulates R2, can regulate gain.R2=1K Ω, amplifier gain is 6.8dB.Regulate R4, can regulate chip current.Therefore, gain and electric current can be controlled respectively.
As shown in Figure 3, R3 is high resistant, and the input of C1 composition high pass, and cut off band width is less than 50Hz.The chip frequency response is low so all can be very smooth to 50Hz.C1 can be adjusted to the 5pF left and right.The R3 resistance is very high, in G Ω magnitude.
As shown in Figure 4, in amplifier of the present invention, high resistant R3 also can use diode (Diode) to realize in zero-bias.
As shown in Figure 5, in amplifier of the present invention, high resistant R3 also can be in accurate transoid bias state realization with PMOS.
Claims (3)
1. an electret (ECM) microphone high-gain preamplifier, is characterized in that adopting the pmos source follower as input, and PNOS M3 size need not be very large, and input capacitance can be controlled in 2pF, just can increase amplifier gain.Adopt the pmos source follower as input, amplifier A input is easy to arrange the DC bias voltage, also adopts in addition the CMOS ic manufacturing technology to reduce manufacturing cost.
2. by a kind of electret claimed in claim 1 (ECM) microphone high-gain preamplifier, it is characterized in that under the effect of differential amplifier A, PMOS M2 grid voltage VG_M2 and PMOS M3 grid voltage VG_M3 equate, electric current I M1=VG_M2/R2=VG_M3/R2 by M1, PMOS M3 grid voltage VG_M3 can regulate by R4, therefore can regulate chip current.
3. by a kind of electret claimed in claim 1 (ECM) microphone high-gain preamplifier, it is characterized in that gain and electric current can control respectively by adjusting R2 and R4 respectively.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011103622027A CN103107782A (en) | 2011-11-14 | 2011-11-14 | High-gain front-arranged amplifier for electret electrochemical machining (ECM) microphone |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2011103622027A CN103107782A (en) | 2011-11-14 | 2011-11-14 | High-gain front-arranged amplifier for electret electrochemical machining (ECM) microphone |
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| Publication Number | Publication Date |
|---|---|
| CN103107782A true CN103107782A (en) | 2013-05-15 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2011103622027A Pending CN103107782A (en) | 2011-11-14 | 2011-11-14 | High-gain front-arranged amplifier for electret electrochemical machining (ECM) microphone |
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Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6160450A (en) * | 1999-04-09 | 2000-12-12 | National Semiconductor Corporation | Self-biased, phantom-powered and feedback-stabilized amplifier for electret microphone |
| CN101339443A (en) * | 2008-08-08 | 2009-01-07 | 武汉大学 | Broad output current scope low pressure difference linear manostat |
| CN101594139A (en) * | 2009-06-22 | 2009-12-02 | 中国科学院微电子研究所 | Buffer based on source follower |
| CN101989842A (en) * | 2009-07-31 | 2011-03-23 | 瑞萨电子株式会社 | Operational amplifier and semiconductor device using the same |
-
2011
- 2011-11-14 CN CN2011103622027A patent/CN103107782A/en active Pending
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6160450A (en) * | 1999-04-09 | 2000-12-12 | National Semiconductor Corporation | Self-biased, phantom-powered and feedback-stabilized amplifier for electret microphone |
| CN101339443A (en) * | 2008-08-08 | 2009-01-07 | 武汉大学 | Broad output current scope low pressure difference linear manostat |
| CN101594139A (en) * | 2009-06-22 | 2009-12-02 | 中国科学院微电子研究所 | Buffer based on source follower |
| CN101989842A (en) * | 2009-07-31 | 2011-03-23 | 瑞萨电子株式会社 | Operational amplifier and semiconductor device using the same |
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Application publication date: 20130515 |