JP2017098744A - Microphone amplifier - Google Patents

Microphone amplifier Download PDF

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JP2017098744A
JP2017098744A JP2015228712A JP2015228712A JP2017098744A JP 2017098744 A JP2017098744 A JP 2017098744A JP 2015228712 A JP2015228712 A JP 2015228712A JP 2015228712 A JP2015228712 A JP 2015228712A JP 2017098744 A JP2017098744 A JP 2017098744A
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amplifier
microphone
diode
input terminal
series
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JP6686259B2 (en
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竜平 根本
Ryuhei Nemoto
竜平 根本
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New Japan Radio Co Ltd
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Abstract

PROBLEM TO BE SOLVED: To provide a microphone amplifier with increased input resistance of an amplifier while preventing the deterioration of ESD resistance.SOLUTION: In the microphone amplifier which includes a capacitor microphone 10, an amplifier 20, and an anti-parallel connection diode 30 which is connected between the input terminal 21 of the amplifier 20 and the ground, a resistor 40 is connected in series to the anti-parallel connection diode 30. Further, between the input terminal 21 of the amplifier 20 and the ground, two anti-parallel connection diodes 50, 60 are connected in series.SELECTED DRAWING: Figure 1

Description

本発明は、コンデンサマイクロホンと増幅器を備えたマイクロホン増幅装置に関する。   The present invention relates to a microphone amplifying apparatus including a condenser microphone and an amplifier.

図３に従来のマイクロホン増幅装置を示す。１０はコンデンサマイクロホン、２０は増幅器である。増幅器２０はコンデンサマイクロホン１０で発生した音声信号を増幅する。７０はＥＳＤ（Electro-Static Discharge：静電気放電）保護用に２個のダイオードを逆並列接続して構成した逆並列接続ダイオードである。このような逆並列接続ダイオードをＥＳＤ保護用に使用するマイクロホン増幅装置として、特許文献１、２に記載がある。   FIG. 3 shows a conventional microphone amplifying apparatus. 10 is a condenser microphone, and 20 is an amplifier. The amplifier 20 amplifies the audio signal generated by the condenser microphone 10. Reference numeral 70 denotes an anti-parallel connected diode configured by connecting two diodes in anti-parallel for ESD (Electro-Static Discharge) protection. Patent Documents 1 and 2 describe microphone amplification devices that use such antiparallel connected diodes for ESD protection.

この逆並列接続ダイオード７０は、ＥＳＤ保護機能の他に、増幅器２０の入力端子２１を高抵抗にして増幅器２０にバイアスを与える働きをしている。抵抗ではなく逆並列接続ダイオード７０を使用する理由は、電源投入直後に比較的短時間で増幅器２０の入力端子２１のバイアスを安定化できること、全体を半導体装置で構成する場合に逆並列接続ダイオード７０の面積が小さくて済むことである。   In addition to the ESD protection function, the antiparallel connection diode 70 functions to make the input terminal 21 of the amplifier 20 have a high resistance so as to bias the amplifier 20. The reason why the antiparallel connection diode 70 is used instead of the resistor is that the bias of the input terminal 21 of the amplifier 20 can be stabilized in a relatively short time immediately after the power is turned on. This means that the area can be small.

ところで、マイクロホン増幅装置のノイズ成分は、増幅器２０自体で発生するノイズと逆並列接続ダイオード７０で発生するノイズの和となる。逆並列接続ダイオード７０で発生するノイズは、図４に示す電流／電圧特性図の０Ｖ付近のダイオード抵抗に依存し、その抵抗値が大きいほどノイズが大きくなる。   By the way, the noise component of the microphone amplifying device is the sum of the noise generated in the amplifier 20 itself and the noise generated in the antiparallel connected diode 70. The noise generated in the antiparallel connected diode 70 depends on the diode resistance in the vicinity of 0V in the current / voltage characteristic diagram shown in FIG. 4, and the noise increases as the resistance value increases.

逆並列接続ダイオード７０の抵抗値が大きくなると、その抵抗成分とコンデンサマイクロホン１０の持っているキャパシタ成分とで構成されるフィルタのカットオフ周波数が低下するので、音声帯域のノイズを抑制して小さくすることができる。   When the resistance value of the antiparallel connected diode 70 is increased, the cutoff frequency of the filter composed of the resistance component and the capacitor component of the capacitor microphone 10 is lowered, so that noise in the voice band is suppressed and reduced. be able to.

特開昭５７−５２１７５号公報JP-A-57-52175 特開２０１１−２３３９５４号公報Japanese Patent Laid-Open No. 2011-233594

そこで、増幅器２０の入力抵抗を大きくするために逆並列接続ダイオード７０のサイズを小さくすることが考えられるが、そのようにすると、ＥＳＤ耐量が低下してしまい破壊し易くなるという問題があった。   Therefore, it is conceivable to reduce the size of the anti-parallel diode 70 in order to increase the input resistance of the amplifier 20, but doing so has a problem that the ESD tolerance is reduced and the diode 20 is easily destroyed.

本発明の目的は、ＥＳＤ耐量の低下を防止しながら増幅器の入力抵抗を大きくできるようにしたマイクロホン増幅装置を提供することである。   An object of the present invention is to provide a microphone amplifying apparatus that can increase the input resistance of an amplifier while preventing a decrease in ESD tolerance.

上記目的を達成するために、請求項１にかかる発明は、コンデンサマイクロホンと、該コンデンサマイクロホンで発生する音声信号を増幅する増幅器と、該増幅器の入力端子と接地との間に接続される第１の逆並列接続ダイオードと、を備えるマイクロホン増幅装置において、前記第１の逆並列接続ダイオードに第１の抵抗を直列接続し、且つ前記増幅器の前記入力端子と前記接地との間に第２の逆並列接続ダイオードを２以上直列接続したことを特徴とする。   To achieve the above object, according to a first aspect of the present invention, there is provided a capacitor microphone, an amplifier for amplifying an audio signal generated by the capacitor microphone, and a first connected between the input terminal of the amplifier and the ground. A first parallel resistor connected in series to the first anti-parallel connection diode, and a second reverse connection between the input terminal of the amplifier and the ground. Two or more parallel-connected diodes are connected in series.

請求項２にかかる発明は、請求項１に記載のマイクロホン増幅装置において、前記第２の逆並列接続ダイオードは、前記第１の逆並列接続ダイオードよりもサイズが大きく設定されていることを特徴とする。   According to a second aspect of the present invention, in the microphone amplifying device according to the first aspect, the second antiparallel connection diode is set to be larger in size than the first antiparallel connection diode. To do.

本発明によれば、第１の逆並列接続ダイオードと第１の抵抗によって増幅器の入力抵抗を大きくし、２個以上並列接続した第２の逆並列接続ダイオードによってＥＳＤ耐量の低下を防止することができる。   According to the present invention, it is possible to increase the input resistance of the amplifier by the first antiparallel connection diode and the first resistor, and to prevent the ESD tolerance from being lowered by the second antiparallel connection diodes connected in parallel by two or more. it can.

本発明の１つの実施例のマイクロホン増幅装置の回路図である。1 is a circuit diagram of a microphone amplifying apparatus according to one embodiment of the present invention. 図１のマイクロホン増幅装置の増幅器の入力端子の電圧／電流特性図である。FIG. 2 is a voltage / current characteristic diagram of an input terminal of an amplifier of the microphone amplifier of FIG. 1. 従来のマイクロホン増幅装置の回路図である。It is a circuit diagram of the conventional microphone amplifier. 図３のマイクロホン増幅装置の増幅器の入力端子の電圧／電流特性図である。FIG. 4 is a voltage / current characteristic diagram of an input terminal of an amplifier of the microphone amplifier of FIG. 3.

図１に本発明の１つの実施例のマイクロホン増幅装置を示す。図３で説明したものと同じものには同じ符号をつけた。本実施例では、増幅器２０の入力端子２１と接地ＧＮＤとの間に、逆並列接続ダイオード３０に抵抗４０を直列接続した直列回路を接続している。さらに、増幅器２０の入力端子２１と接地ＧＮＤとの間に、逆並列接続ダイオード５０，６０を直列接続した直列回路を接続している。   FIG. 1 shows a microphone amplifying apparatus according to one embodiment of the present invention. The same components as those described with reference to FIG. In this embodiment, a series circuit in which a resistor 40 is connected in series to an antiparallel connection diode 30 is connected between the input terminal 21 of the amplifier 20 and the ground GND. Further, a series circuit in which antiparallel connected diodes 50 and 60 are connected in series is connected between the input terminal 21 of the amplifier 20 and the ground GND.

逆並列接続ダイオード３０はサイズが小さく、図３で説明した逆並列接続ダイオード７０よりも高抵抗であり、図２のＡにその電流／電圧特性を示す。この逆並列接続ダイオード３０は抵抗４０と直列接続されており、増幅器２０の入力端子２１の電圧が高くなったときに、そこに流れる電流を抑制する。図２のＢに抵抗４０の電流／電圧特性を示す。   The anti-parallel connection diode 30 is small in size and has a higher resistance than the anti-parallel connection diode 70 described in FIG. 3, and its current / voltage characteristics are shown in FIG. This anti-parallel diode 30 is connected in series with the resistor 40 and suppresses the current flowing therethrough when the voltage at the input terminal 21 of the amplifier 20 becomes high. FIG. 2B shows the current / voltage characteristics of the resistor 40.

逆並列接続ダイオード５０，６０は逆並列接続ダイオード３０よりもサイズが大きく、単体の抵抗値は逆並列接続ダイオード３０よりも小さいが、直列接続することでオン電圧を高くし合計抵抗を大きくしている。図２のＣにその電流／電圧特性を示す。   The reverse parallel connection diodes 50 and 60 are larger in size than the reverse parallel connection diode 30, and the single resistance value is smaller than that of the reverse parallel connection diode 30, but by increasing the ON voltage and increasing the total resistance by connecting them in series. Yes. FIG. 2C shows the current / voltage characteristics.

図２のＤは、以上説明した電流／電圧特性Ａ，Ｂ，Ｃを合成した電流／電圧特性である。この特性で明らかなように、増幅器２０の入力端子２１と接地ＧＮＤとの間には、高抵抗で高いＥＳＤ耐量を備えた回路が接続されることになり、ＥＳＤ耐量を大きくしながら増幅器の入力抵抗を大きくすることができる。   D in FIG. 2 is a current / voltage characteristic obtained by combining the current / voltage characteristics A, B, and C described above. As apparent from this characteristic, a circuit having a high resistance and a high ESD tolerance is connected between the input terminal 21 of the amplifier 20 and the ground GND, and the input of the amplifier is increased while increasing the ESD tolerance. The resistance can be increased.

つまり、逆並列接続ダイオード３０と抵抗４０によって増幅器２０の入力端子２１の抵抗を大きくし、逆並列接続ダイオード５０，６０によってＥＳＤ耐量を大きくすることができる。   That is, the resistance of the input terminal 21 of the amplifier 20 can be increased by the anti-parallel connection diode 30 and the resistor 40, and the ESD tolerance can be increased by the anti-parallel connection diodes 50 and 60.

なお、逆並列接続ダイオード３０と抵抗４０の接続順は逆であってもよい。また、上記では２個の逆並列接続ダイオード５０，６０を直列接続したが、直列接続する逆並列接続ダイオードは３個以上であってもよい。   Note that the connection order of the antiparallel connection diode 30 and the resistor 40 may be reversed. In the above description, the two anti-parallel connection diodes 50 and 60 are connected in series. However, the number of anti-parallel connection diodes connected in series may be three or more.

１０：コンデンサマイクロホン
２０：増幅器、２１：入力端子
３０，５０，６０，７０：逆並列接続ダイオード
４０：抵抗 10: condenser microphone 20: amplifier, 21: input terminal 30, 50, 60, 70: diode connected in reverse parallel 40: resistance

Claims (2)

コンデンサマイクロホンと、該コンデンサマイクロホンで発生する音声信号を増幅する増幅器と、該増幅器の入力端子と接地との間に接続される第１の逆並列接続ダイオードと、を備えるマイクロホン増幅装置において、
前記第１の逆並列接続ダイオードに第１の抵抗を直列接続し、且つ前記増幅器の前記入力端子と前記接地との間に第２の逆並列接続ダイオードを２以上直列接続したことを特徴とするマイクロホン増幅装置。 In a microphone amplifying apparatus comprising: a capacitor microphone; an amplifier that amplifies an audio signal generated by the capacitor microphone; and a first antiparallel connection diode connected between the input terminal of the amplifier and the ground.
A first resistor is connected in series to the first antiparallel connection diode, and two or more second antiparallel connection diodes are connected in series between the input terminal of the amplifier and the ground. Microphone amplifier. 請求項１に記載のマイクロホン増幅装置において、
前記第２の逆並列接続ダイオードは、前記第１の逆並列接続ダイオードよりもサイズが大きく設定されていることを特徴とするマイクロホン増幅装置。 The microphone amplifying device according to claim 1,
The microphone amplifying apparatus according to claim 1, wherein the second antiparallel connection diode is set larger in size than the first antiparallel connection diode.
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Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006041441A (en) * 2004-07-30 2006-02-09 New Japan Radio Co Ltd Semiconductor device
US20130129117A1 (en) * 2011-11-21 2013-05-23 Henrik Thomsen Audio amplification circuit

Patent Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2006041441A (en) * 2004-07-30 2006-02-09 New Japan Radio Co Ltd Semiconductor device
US20130129117A1 (en) * 2011-11-21 2013-05-23 Henrik Thomsen Audio amplification circuit

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