WO2003086014A1 - Impedance converter for capacitor microphone - Google Patents

Impedance converter for capacitor microphone Download PDF

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Publication number
WO2003086014A1
WO2003086014A1 PCT/JP2002/003623 JP0203623W WO03086014A1 WO 2003086014 A1 WO2003086014 A1 WO 2003086014A1 JP 0203623 W JP0203623 W JP 0203623W WO 03086014 A1 WO03086014 A1 WO 03086014A1
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Prior art keywords
capacitor
impedance converter
source follower
resistor
power supply
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PCT/JP2002/003623
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French (fr)
Japanese (ja)
Inventor
Takashi Yamasaki
Original Assignee
Rion Co.,Ltd
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Publication date
Application filed by Rion Co.,Ltd filed Critical Rion Co.,Ltd
Priority to AU2002255260A priority Critical patent/AU2002255260A1/en
Priority to JP2003583055A priority patent/JP4024213B2/en
Priority to PCT/JP2002/003623 priority patent/WO2003086014A1/en
Publication of WO2003086014A1 publication Critical patent/WO2003086014A1/en

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    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/50—Amplifiers in which input is applied to, or output is derived from, an impedance common to input and output circuits of the amplifying element, e.g. cathode follower
    • H03F3/505—Amplifiers in which input is applied to, or output is derived from, an impedance common to input and output circuits of the amplifying element, e.g. cathode follower with field-effect devices
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F3/00—Amplifiers with only discharge tubes or only semiconductor devices as amplifying elements
    • H03F3/181—Low-frequency amplifiers, e.g. audio preamplifiers
    • H03F3/183—Low-frequency amplifiers, e.g. audio preamplifiers with semiconductor devices only
    • H03F3/185—Low-frequency amplifiers, e.g. audio preamplifiers with semiconductor devices only with field-effect devices
    • H03F3/1855—Low-frequency amplifiers, e.g. audio preamplifiers with semiconductor devices only with field-effect devices with junction-FET devices
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04R—LOUDSPEAKERS, MICROPHONES, GRAMOPHONE PICK-UPS OR LIKE ACOUSTIC ELECTROMECHANICAL TRANSDUCERS; DEAF-AID SETS; PUBLIC ADDRESS SYSTEMS
    • H04R3/00—Circuits for transducers, loudspeakers or microphones
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2200/00—Indexing scheme relating to amplifiers
    • H03F2200/03—Indexing scheme relating to amplifiers the amplifier being designed for audio applications
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2200/00—Indexing scheme relating to amplifiers
    • H03F2200/219—Follower transistors are added at the input of the amplifier, e.g. source or emitter followers
    • H—ELECTRICITY
    • H03—ELECTRONIC CIRCUITRY
    • H03F—AMPLIFIERS
    • H03F2200/00—Indexing scheme relating to amplifiers
    • H03F2200/222—A circuit being added at the input of an amplifier to adapt the input impedance of the amplifier

Definitions

  • the present invention relates to an impedance converter incorporated in a small condenser microphone used for a hearing aid or the like.
  • a source follower circuit using a field effect transistor FET
  • FET field effect transistor
  • the impedance converter has a JFET or M ⁇ ⁇ ⁇ SFET transistor chip mounted on a ceramic substrate, a firing resistor is formed on the ceramic substrate, and a chip component is mounted on the capacitor. Or, it was realized as a hybrid circuit by forming a ferroelectric film on a ceramics substrate by sandwiching it between vapor deposition layers.
  • the impedance converter is formed as a hybrid circuit on a ceramic substrate
  • the size of the hybrid circuit formed on the ceramic substrate hinders miniaturization when the hearing aid microphone is miniaturized.
  • the present invention has been made in view of the above-mentioned problems of the conventional technology, and an object thereof is to prevent a surge voltage such as electrostatic discharge from being directly applied to a capacitor, and to provide a capacitor having a low withstand voltage.
  • the aim is to provide an impedance converter for condenser microphones that can withstand surge voltages and that can be downsized.
  • the invention according to claim 1 is an impedance converter for reducing an output impedance of a condenser microphone with respect to an electric signal, and uses a field effect transistor (FET).
  • FET field effect transistor
  • a source follower circuit is provided, and resistors Rl and R2 are connected in series to a power supply line and an output signal line of the source follower circuit, respectively, and the power supply on the source follower circuit side of these resistors Rl and R2 is provided.
  • Capacitors C1 and C2 were connected between the line and output signal line and Durand line, respectively.
  • An invention according to claim 2 is the impedance converter for a condenser microphone according to claim 1, wherein the filter includes a resistor R1 connected to the power supply line and a capacitor C1.
  • the cut-off frequency of the circuit and the cut-off frequency of the filter circuit constituted by the resistor R2 and the capacitor C2 connected to the output signal line were made substantially equal.
  • the invention according to claim 3 is the impedance converter for a capacitor microphone according to claim 1 or 2, comprising the source follower circuit, the resistor R1, and the capacitor C1. And a filter circuit composed of the resistor R2 and the capacitor C2 are formed in one chip on the same silicon substrate.
  • FIG. 1 is a circuit diagram of an impedance converter for a condenser microphone according to the present invention.
  • FIG. 1 is a circuit diagram of an impedance converter for a condenser microphone according to the present invention.
  • an impedance converter 1 for a condenser microphone according to the present invention includes a source follower circuit 5 including a field effect transistor (FET) 2 and resistors 3 and 4, and a power supply line 6 of the source follower circuit 5.
  • FET field effect transistor
  • the resistors R1 and R2 connected in series to the output signal line 7, respectively, and the resistors R1 and R2 connected between the power supply line 6 on the source follower circuit 5 side and the output signal line 7 and the ground line 8, respectively.
  • It has capacitors C1 and C2.
  • 9 is a condenser microphone
  • 10 is a power supply terminal
  • 11 is an output terminal
  • 12 is a ground terminal.
  • a one-pass filter circuit 13 is formed by the resistor R1 and the capacitor C1 connected to the power supply line 6, and a one-pass filter circuit 14 is formed by the resistor R2 and the capacitor C2 connected to the output signal line 7.
  • the cut-off frequency of the low-pass filter circuit 13 and the cut-off frequency of the low-pass filter circuit 14 are equal, and the cut-off frequency is lower than the frequency of the high-frequency electromagnetic waves received as jamming radio waves.
  • the value of the capacitance of C2 is determined.
  • the resistance value of the resistor R1 and the resistance value of the resistor R2 may not be equal, and the capacitance value of the capacitor C1 and the capacitance value of the capacitor C2 may not be equal.
  • the acoustic signal is converted into an electric signal by the condenser microphone 9, and the obtained electric signal is input to the FET 2 of the source follower circuit 5. Then, the output impedance of the condenser microphone 9 with respect to the electric signal is reduced by the FET2. The electric signal is output from the output terminal 11 via the resistor R2 and the output signal line 7.
  • the source follower circuit 5 can carry out impedance conversion of the electric signal from the condenser microphone 9 and detect it from the output terminal 11 without detecting the interfering radio wave due to the high-frequency electromagnetic wave.
  • the surge voltage is first applied to the resistors R 1 and R 2, and heat energy is generated inside the resistors R l and R 2.
  • the surge voltage is applied to the capacitors CI and C2 with their peak value reduced.
  • the surge voltage is not directly applied to the capacitors CI and C2, so there is no need to provide a high withstand voltage, and the capacitors C1 and C2 do not require excessive quality unrelated to the function of the impedance converter. I'm done.
  • the resistance value of the resistors R l and R 2 increases.
  • the impedance converter is a battery-powered hearing aid. When used in such devices, it is equivalent to increasing the internal resistance of the battery, so applying it to them is disadvantageous. Therefore, when the impedance converter is applied to a battery-driven product such as a hearing aid, the resistance value of the resistor R1 provided on the power supply line 6 needs to be reduced to such an extent that it is not disadvantageous in use. Further, even if the resistance value of the resistor R2 provided in the output signal line 7 is not as small as the resistance value of the resistor R1, the influence on the applied device is small.
  • the resistance of the resistor R 2 can be increased to make it more robust against surge voltages. Therefore, the resistance value of the resistor R1 provided on the power supply line 6 and the resistance value of the resistor R2 provided on the output signal line 7 do not need to be equal.
  • the impedance converter 1 for a condenser microphone includes a source follower circuit 5, a low-pass filter circuit 13 including a resistor R1 and a capacitor Cn, a resistor R2 and a capacitor C2.
  • One-pass filter circuit 14 is formed in one chip on the same silicon substrate. The size of the crophone can be easily reduced. Industrial applicability
  • the surge voltage is first applied to the resistors R1 and R2, The surge voltage is consumed as heat energy inside the resistors R l and R 2, and the surge voltage is applied to the capacitors C l and C 2 with their peak values reduced, so that the surge voltage is applied to the capacitors C l and C 2. Since it is not applied directly, there is no need to provide a high withstand voltage, and capacitors C l and C 2 do not need to have excessive quality that is not related to the function of the impedance converter.
  • the disturbing radio wave caused by the high-frequency electromagnetic wave between the power supply line and the ground line and the disturbing radio wave caused by the high-frequency electromagnetic wave between the output signal line and the ground line are reduced equally.
  • noise output from the source follower circuit due to high-frequency electromagnetic waves can be prevented.

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Physics & Mathematics (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Multimedia (AREA)
  • Circuit For Audible Band Transducer (AREA)
  • Networks Using Active Elements (AREA)
  • Amplifiers (AREA)
  • Electrostatic, Electromagnetic, Magneto- Strictive, And Variable-Resistance Transducers (AREA)

Abstract

An impedance converter for capacitor microphone in which a surge voltage of electrostatic discharge, or the like, is not applied directly to a capacitor and even a capacitor having a low withstand voltage can endure against the surge voltage while reducing the size. The impedance converter (1) reduces the output impedance concerning to the electric signal of a capacitor microphone (9) and comprises a source follower circuit (5) employing a field effect transistor (FET) 2. The source follower circuit (5) has a power supply line (6) and an output signal line (7) connected in series with resistors R1 and R2, respectively, and capacitors C1 and C2 are connected between a ground line (8)and the power supply line (6) and the output signal line (7), respectively, on the source follower circuit (5) side of the resistors R1 and R2.

Description

明細^ コンデンサマイクロホン用インピ一ダンス変換器 技術分野  Description ^ Impedance converter for condenser microphone
本発明は、 補聴器などに用いられる小型のコンデンサマイクロホンに組み込む インピーダンス変換器に関する。 背景技術  The present invention relates to an impedance converter incorporated in a small condenser microphone used for a hearing aid or the like. Background art
従来のコンデンサマイクロホンの電気信号に関する出力インピーダンスを低減 するインピーダンス変換器としては、 米国特許第 6084972号に記載のように、 電 界効果型トランジスタ （F E T) を用いたソ一スフォロワ回路を備え、 このソ一 スフォロワ回路の電源線及び出力信号線とグランド線との間に夫々 3 0 p Fのコ ンデンサを接続したものが知られている。 これらのコンデンサは基板上に直接誘 電率の高い絶縁体を回路パターンで挟み込んで実装され、 これにより高周波電磁 波妨害を受け難くしている。  As described in U.S. Pat. No. 6,084,972, as an impedance converter for reducing the output impedance related to the electric signal of a conventional condenser microphone, a source follower circuit using a field effect transistor (FET) is provided. It is known that a 30 pF capacitor is connected between a power line and an output signal line of a follower circuit and a ground line, respectively. These capacitors are mounted directly on the substrate with an insulator with a high dielectric constant sandwiched between circuit patterns, thereby making it less susceptible to high-frequency electromagnetic interference.
また、 従来の補聴器用マイクロホンにおいて、 そのインピーダンス変換器は、 セラミックス基板上に J F E Tまたは M〇S F E Tのトランジスタチップを搭載 し、 セラミックス基板上に焼成抵抗を形成し、 コンデンサについてはチップ部品 を搭載するか、 または強誘電体の膜を蒸着層で挟み込むことによってセラミック ス基板上に形成することによりハイプリット回路として実現していた。  In a conventional hearing aid microphone, the impedance converter has a JFET or M ま た は SFET transistor chip mounted on a ceramic substrate, a firing resistor is formed on the ceramic substrate, and a chip component is mounted on the capacitor. Or, it was realized as a hybrid circuit by forming a ferroelectric film on a ceramics substrate by sandwiching it between vapor deposition layers.
しかし、 従来のインピーダンス変換器においては、 高周波電磁波妨害を除去す るために電源線、 出力信号線及びダランド線の高周波電磁波に対する電位の変化 を等しく低減することで、 電源線、 出力信号線及びグランド線の電位のアンバラ ンスな変化をなくし、 高周波電磁波によるソースフォロワ回路からの雑音の出力 を防ぐ必要がある。 そのため電源線とグランド線の間に設けたコンデンサの静電 容量と、 出力信号線とグランド線の間に設けたコンデンサの静電容量を等しくす る必要がある。 この状態では、 インピーダンス変換器の端子に静電気放電などの サージ電圧が加わると、 直接コンデンサに高電圧が印加することになるので、 コ ンデンサの耐圧を上げる必要がある。 However, in conventional impedance converters, in order to eliminate high-frequency electromagnetic interference, power supply lines, output signal lines, and ground lines are equally reduced in potential change with respect to high-frequency electromagnetic waves, so that power supply lines, output signal lines, and grounds are reduced. It is necessary to eliminate unbalanced changes in line potential and to prevent noise output from the source follower circuit due to high-frequency electromagnetic waves. Therefore, it is necessary to make the capacitance of the capacitor provided between the power supply line and the ground line equal to the capacitance of the capacitor provided between the output signal line and the ground line. In this state, if a surge voltage such as electrostatic discharge is applied to the terminals of the impedance converter, a high voltage will be applied directly to the capacitor. It is necessary to increase the withstand voltage of the capacitor.
また、 インピーダンス変換器をセラミックス基板上にハイプリット回路として 形成した場合には、 補聴器用マイクロホンを小型化する際に、 そのセラミックス 基板上に形成したハイブリット回路の基板寸法が小型化を妨げてしまうという問 題がある。  In addition, when the impedance converter is formed as a hybrid circuit on a ceramic substrate, the size of the hybrid circuit formed on the ceramic substrate hinders miniaturization when the hearing aid microphone is miniaturized. There is a title.
本発明は、 従来の技術が有するこのような問題点に鑑みてなされたものであり、 その目的とするところは、 静電気放電などのサージ電圧がコンデンサに直接加わ ることがなく、 耐圧が低いコンデンサでもサージ電圧に耐えられ、 しかも小型化 が図れるコンデンサマイクロホン用インピーダンス変換器を提供しょうとするも のである。 発明の開示 - 上記課題を解決すべく請求の範囲第 1項に係る発明は、 コンデンサマイクロホ ンの電気信号に関する出力インピーダンスを低減するインピーダンス変換器であ つて、 電界効果型トランジスタ （F E T) を用いたソースフォロワ回路を備え、 このソ一スフォロワ回路の電源線及び出力信号線に夫々抵抗 R l, R 2を直列に接 続し、 これらの抵抗 R l， R 2の前記ソースフォロワ回路側の前記電源線及び出力 信号線とダランド線との間に夫々コンデンサ C 1， C 2を接続した。  The present invention has been made in view of the above-mentioned problems of the conventional technology, and an object thereof is to prevent a surge voltage such as electrostatic discharge from being directly applied to a capacitor, and to provide a capacitor having a low withstand voltage. However, the aim is to provide an impedance converter for condenser microphones that can withstand surge voltages and that can be downsized. DISCLOSURE OF THE INVENTION-To solve the above-mentioned problems, the invention according to claim 1 is an impedance converter for reducing an output impedance of a condenser microphone with respect to an electric signal, and uses a field effect transistor (FET). A source follower circuit is provided, and resistors Rl and R2 are connected in series to a power supply line and an output signal line of the source follower circuit, respectively, and the power supply on the source follower circuit side of these resistors Rl and R2 is provided. Capacitors C1 and C2 were connected between the line and output signal line and Durand line, respectively.
請求の範囲第 2項に係る発明は、 請求の範囲第 1項に記載のコンデンサマイク 口ホン用インピーダンス変換器において、 前記電源線に接続された抵抗 R 1とコ ンデンサ C 1により構成されるフィルタ回路のカツトオフ周波数と、 前記出力信 号線に接続された抵抗 R 2とコンデンサ C 2により構成されるフィル夕回路のカツ トオフ周波数をほぼ等しくした。  An invention according to claim 2 is the impedance converter for a condenser microphone according to claim 1, wherein the filter includes a resistor R1 connected to the power supply line and a capacitor C1. The cut-off frequency of the circuit and the cut-off frequency of the filter circuit constituted by the resistor R2 and the capacitor C2 connected to the output signal line were made substantially equal.
請求の範囲第 3項に係る発明は、 請求の範囲第 1項又は第 2項に記載のコンデ ンサマイクロホン用インピーダンス変換器において、 前記ソ一スフォロワ回路と、 前記抵抗 R 1とコンデンサ C 1により構成されるフィルタ回路と、 前記抵抗 R 2と コンデンサ C 2により構成されるフィル夕回路が、 同一シリコン基板上にワンチ ップで形成される。 図面の簡単な説明 The invention according to claim 3 is the impedance converter for a capacitor microphone according to claim 1 or 2, comprising the source follower circuit, the resistor R1, and the capacitor C1. And a filter circuit composed of the resistor R2 and the capacitor C2 are formed in one chip on the same silicon substrate. BRIEF DESCRIPTION OF THE FIGURES
第 1図は、 本発明に係るコンデンサマイクロホン用インピーダンス変換器の回 路図である。 発明を実施するための最良の形態  FIG. 1 is a circuit diagram of an impedance converter for a condenser microphone according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION
以下に本発明の実施の形態を添付図面に基づいて説明する。 ここで、 第 1図は 本発明に係るコンデンサマイクロホン用インピーダンス変換器の回路図である。 第 1図に示すように、 本発明に係るコンデンサマイクロホン用インピーダンス 変換器 1は、 電界効果型トランジスタ （FET) 2と抵抗 3, 4からなるソース フォロワ回路 5と、 ソースフォロワ回路 5の電源線 6及び出力信号線 7に夫々直 列に接続した抵抗 Rl， R2と、 これらの抵抗 Rl， R2のソースフォロワ回路 5側 の電源線 6及び出力信号線 7とグランド線 8との間に夫々接続したコンデンサ C 1, C2を備えている。 なお、 9はコンデンサマイクロホン、 10は電源端子、 1 1は出力端子、 12はグランド端子である。  Embodiments of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a circuit diagram of an impedance converter for a condenser microphone according to the present invention. As shown in FIG. 1, an impedance converter 1 for a condenser microphone according to the present invention includes a source follower circuit 5 including a field effect transistor (FET) 2 and resistors 3 and 4, and a power supply line 6 of the source follower circuit 5. And the resistors R1 and R2 connected in series to the output signal line 7, respectively, and the resistors R1 and R2 connected between the power supply line 6 on the source follower circuit 5 side and the output signal line 7 and the ground line 8, respectively. It has capacitors C1 and C2. 9 is a condenser microphone, 10 is a power supply terminal, 11 is an output terminal, and 12 is a ground terminal.
そして、 電源線 6に接続された抵抗 R1とコンデンサ C1により口一パスフィル 夕回路 13を構成し、 出力信号線 7に接続された抵抗 R2とコンデンサ C2により 口一パスフィルタ回路 14を構成する。 ローパスフィルタ回路 13のカツトオフ 周波数と、 ローパスフィルタ回路 14のカツトオフ周波数は等しくなるよう且つ、 カツトオフ周波数が妨害電波として受ける高周波電磁波の周波数より低くなるよ う、 抵抗 Ri, R2の抵抗値とコンデンサ Cl， C2の静電容量の値が決定される。 抵抗 R 1の抵抗値と抵抗 R 2の抵抗値は等しくなくてもよく、 コンデンサ C 1の静 電容量の値とコンデンサ C 2の静電容量の値は等しくなくてもよい。  A one-pass filter circuit 13 is formed by the resistor R1 and the capacitor C1 connected to the power supply line 6, and a one-pass filter circuit 14 is formed by the resistor R2 and the capacitor C2 connected to the output signal line 7. The cut-off frequency of the low-pass filter circuit 13 and the cut-off frequency of the low-pass filter circuit 14 are equal, and the cut-off frequency is lower than the frequency of the high-frequency electromagnetic waves received as jamming radio waves. The value of the capacitance of C2 is determined. The resistance value of the resistor R1 and the resistance value of the resistor R2 may not be equal, and the capacitance value of the capacitor C1 and the capacitance value of the capacitor C2 may not be equal.
以上のように構成した本発明に係るコンデンサマイクロホン用インピーダンス 変換器 1の動作について説明する。  The operation of the thus configured impedance converter 1 for a condenser microphone according to the present invention will be described.
音響信号がコンデンサマイクロホン 9で電気信号に変換され、 得られた電気信 号がソ一スフォロワ回路 5の FET 2に入力する。 すると、 コンデンサマイクロ ホン 9の電気信号に関する出力インピーダンスは、 F ET 2によって低減される。 電気信号は抵抗 R2と出力信号線 7を介して出力端子 11より出力される。  The acoustic signal is converted into an electric signal by the condenser microphone 9, and the obtained electric signal is input to the FET 2 of the source follower circuit 5. Then, the output impedance of the condenser microphone 9 with respect to the electric signal is reduced by the FET2. The electric signal is output from the output terminal 11 via the resistor R2 and the output signal line 7.
抵抗 R1とコンデンサ C1による口一パスフィルタ回路 13と抵抗 R2とコンデ ンサ C 2によるローパスフィルタ回路 1 4のカツトオフ周波数は、 妨害電波とし て受ける高周波電磁波の周波数より低く設定されているため、 電源線 6とグラン ド線 8との間の高周波電磁波による妨害電波と、 出力信号線 7とグランド線 8と の間の高周波電磁波による妨害電波を等しく低減し、 高周波電磁波によるソース フォロワ回路 5からの雑音の出力を防ぐことができる。 Single pass filter circuit 13 with resistor R1 and capacitor C1, capacitor R1 and capacitor Since the cut-off frequency of the low-pass filter circuit 14 using the sensor C 2 is set lower than the frequency of the high-frequency electromagnetic waves received as the interfering radio waves, This makes it possible to equally reduce interference radio waves caused by high-frequency electromagnetic waves between the output signal line 7 and the ground line 8 and prevent noise output from the source follower circuit 5 due to high-frequency electromagnetic waves.
これによつて、 ソ一スフォロワ回路 5は高周波電磁波による妨害電波を検波す ることなくコンデンサマイクロホン 9からの電気信号をィンピ一ダンス変換して 出力端子 1 1より出力することができる。 この時、 電源端子 1 0及び出力端子 1 1に静電気などによるサージ電圧が印加されたとしても、 サージ電圧は先ず抵抗 R 1及び抵抗 R 2に加わり、 抵抗 R l, R 2の内部で熱エネルギーとして消費され、 サージ電圧はその波高値を減じてコンデンサ C I, C 2に印加される。  As a result, the source follower circuit 5 can carry out impedance conversion of the electric signal from the condenser microphone 9 and detect it from the output terminal 11 without detecting the interfering radio wave due to the high-frequency electromagnetic wave. At this time, even if a surge voltage due to static electricity or the like is applied to the power supply terminal 10 and the output terminal 11, the surge voltage is first applied to the resistors R 1 and R 2, and heat energy is generated inside the resistors R l and R 2. The surge voltage is applied to the capacitors CI and C2 with their peak value reduced.
従って、 コンデンサ C I , C 2には、 サージ電圧が直接印加されないため高い耐 圧を持たせる必要がなく、 インピーダンス変換器の機能とは関係ない過剰な品質 をコンデンサ C l， C 2に求めなくて済む。  Therefore, the surge voltage is not directly applied to the capacitors CI and C2, so there is no need to provide a high withstand voltage, and the capacitors C1 and C2 do not require excessive quality unrelated to the function of the impedance converter. I'm done.
また、 抵抗 R l， R 2の抵抗値を大きくすることによりサージ電圧に対して強靭 になるが、 電源線 6に直列に大きな抵抗を接続するのは、 インピ一ダンス変換器 が電池駆動の補聴器などの機器に使用された場合、 電池の内部抵抗を大きくする のと等価に作用するため、 それらに適用するのは不利となる。 従って、 電源線 6 に設けた抵抗 R 1の抵抗値は、 補聴器などの電池駆動の製品にィンピーダンス変 換器を適用する場合には、 使用上不利にならない程度に小さくする必要がある。 また、 出力信号線 7に設けた抵抗 R 2の抵抗値は、 抵抗 R 1の抵抗値ほど小さく なくても適用する機器に影響を与えることが少ない。 従って、 抵抗 R 2の抵抗値 は、 サージ電圧に対してより強靭にするため大きくすることができる。 よって、 電源線 6に設けた抵抗 R 1の抵抗値と出力信号線 7に設けた抵抗 R 2の抵抗値は、 等しくする必要はない。  In addition, by increasing the resistance values of the resistors R l and R 2, the resistance to surge voltage increases. However, connecting a large resistor in series to the power supply line 6 is because the impedance converter is a battery-powered hearing aid. When used in such devices, it is equivalent to increasing the internal resistance of the battery, so applying it to them is disadvantageous. Therefore, when the impedance converter is applied to a battery-driven product such as a hearing aid, the resistance value of the resistor R1 provided on the power supply line 6 needs to be reduced to such an extent that it is not disadvantageous in use. Further, even if the resistance value of the resistor R2 provided in the output signal line 7 is not as small as the resistance value of the resistor R1, the influence on the applied device is small. Therefore, the resistance of the resistor R 2 can be increased to make it more robust against surge voltages. Therefore, the resistance value of the resistor R1 provided on the power supply line 6 and the resistance value of the resistor R2 provided on the output signal line 7 do not need to be equal.
また、 本発明に係るコンデンサマイクロホン用インピーダンス変換器 1は、 ソ 一スフォロワ回路 5と、 抵抗 R 1とコンデンサ C nこより構成されるローパスフィ ルタ回路 1 3と、 抵抗 R 2とコンデンサ C 2により構成される口一パスフィルタ回 路 1 4が、 同一のシリコン基板上にワンチップで形成されるので、 補聴器用マイ クロホンの小型化を容易にすることができる。 産業上の利用可能性 The impedance converter 1 for a condenser microphone according to the present invention includes a source follower circuit 5, a low-pass filter circuit 13 including a resistor R1 and a capacitor Cn, a resistor R2 and a capacitor C2. One-pass filter circuit 14 is formed in one chip on the same silicon substrate. The size of the crophone can be easily reduced. Industrial applicability
以上説明したように請求の範囲第 1項に係る発明によれば、 電源線及び出力 信号線に静電気などによるサージ電圧が印加されたとしても、 サージ電圧は先ず 抵抗 R 1及び抵抗 R2に加わり、 抵抗 R l, R 2の内部で熱エネルギーとして消費さ れ、 サージ電圧はその波高値を減じてコンデンサ C l， C 2に印加されるため、 コ ンデンサ C l， C 2には、 サージ電圧が直接印加されないため高い耐圧を持たせる 必要がなく、 ィンピーダンス変換器の機能とは関係ない過剰な品質をコンデンサ C l， C 2に求めなくて済む。  As described above, according to the invention of claim 1, even if a surge voltage due to static electricity or the like is applied to the power supply line and the output signal line, the surge voltage is first applied to the resistors R1 and R2, The surge voltage is consumed as heat energy inside the resistors R l and R 2, and the surge voltage is applied to the capacitors C l and C 2 with their peak values reduced, so that the surge voltage is applied to the capacitors C l and C 2. Since it is not applied directly, there is no need to provide a high withstand voltage, and capacitors C l and C 2 do not need to have excessive quality that is not related to the function of the impedance converter.
請求の範囲第 2項に係る発明によれば、 電源線とグランド線との間の高周波電 磁波による妨害電波と、 出力信号線とグランド線との間の高周波電磁波による妨 害電波を等しく低減し、 高周波電磁波によるソースフォロワ回路からの雑音の出 力を防ぐことができる。  According to the invention set forth in claim 2, the disturbing radio wave caused by the high-frequency electromagnetic wave between the power supply line and the ground line and the disturbing radio wave caused by the high-frequency electromagnetic wave between the output signal line and the ground line are reduced equally. However, noise output from the source follower circuit due to high-frequency electromagnetic waves can be prevented.
請求の範囲第 3項に係る発明によれば、 補聴器用マイクロホンの小型化を促進 することが容易にできる。  According to the invention set forth in claim 3, it is easy to promote downsizing of the hearing aid microphone.

Claims

： '；請求の範囲 : ';The scope of the claims
1 . コンデンサマイクロホンの電気信号に関する出力インピーダンスを低減す るインピーダンス変換器であって、 電界効果型トランジスタ （F E T) を用いた ソースフォロワ回路を備え、 このソースフォロワ回路の電源線及び出力信号線に 夫々抵抗 R l， R 2を直列に接続し、 これらの抵抗 R l, R2の前記ソースフォロワ 回路側の前記電源線及び出力信号線とグランド線との間に夫々コンデンサ C 1， C 2を接続したことを特徴とするコンデンサマイクロホン用インピーダンス変換 器。 1. An impedance converter that reduces the output impedance of a condenser microphone with respect to the electric signal. The impedance converter includes a source follower circuit using a field effect transistor (FET). The source follower circuit has a power supply line and an output signal line, respectively. Resistors R 1 and R 2 were connected in series, and capacitors C 1 and C 2 were connected between the power supply line and the output signal line on the source follower circuit side of these resistors R 1 and R 2 and the ground line, respectively. An impedance converter for a condenser microphone, characterized in that:
2 . 請求の範囲第 1項に記載のコンデンサマイクロホン用インピーダンス変換 器において、 前記電源線に接続された抵抗 R 1とコンデンサ C 1により構成される フィル夕回路のカツトオフ周波数が、 前記出力信号線に接続された抵抗 R 2とコ ンデンサ C 2により構成されるフィルタ回路のカツトオフ周波数とほぼ等しいこ とを特徴とするコンデンサマイクロホン用インピーダンス変換器。  2. The impedance converter for a condenser microphone according to claim 1, wherein a cut-off frequency of a filter circuit formed by a resistor R1 and a capacitor C1 connected to the power supply line is connected to the output signal line. An impedance converter for a condenser microphone, characterized by having a cut-off frequency substantially equal to a cut-off frequency of a filter circuit composed of a connected resistor R2 and a capacitor C2.
3 . 請求の範囲第 1項又は第 2項に記載のコンデンサマイクロホン用インピー ダンス変換器において、 前記ソースフォロワ回路と、 前記抵抗 R 1とコンデンサ C 1により構成されるフィルタ回路と、 前記抵抗 R 2とコンデンサ C 2により構成 されるフィル夕回路が、 同一シリコン基板上にワンチップで形成されることを特 徴とするコンデンサマイクロホン用インピーダンス変換器。  3. The impedance converter for a condenser microphone according to claim 1 or 2, wherein the source follower circuit, a filter circuit including the resistor R1 and the capacitor C1, and the resistor R2. An impedance converter for condenser microphones, characterized in that a filter circuit composed of a capacitor and a capacitor C2 is formed in one chip on the same silicon substrate.
PCT/JP2002/003623 2002-04-11 2002-04-11 Impedance converter for capacitor microphone WO2003086014A1 (en)

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Publication number Priority date Publication date Assignee Title
EP2104373A1 (en) * 2008-03-13 2009-09-23 Kabushiki Kaisha Audio- Technica Condenser microphone

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Publication number Priority date Publication date Assignee Title
US4280018A (en) * 1979-05-14 1981-07-21 Strobotronix, Inc. Integrated piezoelectric sound transducer and preamplifier
JPS61128615A (en) * 1984-11-28 1986-06-16 Matsushita Electric Ind Co Ltd Head amplifier
US4993072A (en) * 1989-02-24 1991-02-12 Lectret S.A. Shielded electret transducer and method of making the same
US6084972A (en) * 1996-04-03 2000-07-04 Microtronic Nederland B.V. Integrated microphone/amplifier unit, and amplifier module therefor

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4280018A (en) * 1979-05-14 1981-07-21 Strobotronix, Inc. Integrated piezoelectric sound transducer and preamplifier
JPS61128615A (en) * 1984-11-28 1986-06-16 Matsushita Electric Ind Co Ltd Head amplifier
US4993072A (en) * 1989-02-24 1991-02-12 Lectret S.A. Shielded electret transducer and method of making the same
US6084972A (en) * 1996-04-03 2000-07-04 Microtronic Nederland B.V. Integrated microphone/amplifier unit, and amplifier module therefor

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2104373A1 (en) * 2008-03-13 2009-09-23 Kabushiki Kaisha Audio- Technica Condenser microphone
JP2009224839A (en) * 2008-03-13 2009-10-01 Audio Technica Corp Condenser microphone
US8126165B2 (en) 2008-03-13 2012-02-28 Kabushiki Kaisha Audio-Technica Condenser microphone

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JPWO2003086014A1 (en) 2005-08-18
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