JPH026699Y2 - - Google Patents
Info
- Publication number
- JPH026699Y2 JPH026699Y2 JP10884382U JP10884382U JPH026699Y2 JP H026699 Y2 JPH026699 Y2 JP H026699Y2 JP 10884382 U JP10884382 U JP 10884382U JP 10884382 U JP10884382 U JP 10884382U JP H026699 Y2 JPH026699 Y2 JP H026699Y2
- Authority
- JP
- Japan
- Prior art keywords
- circuit
- preamplifier
- negative feedback
- amount
- input
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
- 239000003990 capacitor Substances 0.000 claims description 10
- 230000008859 change Effects 0.000 claims description 6
- 230000008878 coupling Effects 0.000 claims description 5
- 238000010168 coupling process Methods 0.000 claims description 5
- 238000005859 coupling reaction Methods 0.000 claims description 5
- 230000007423 decrease Effects 0.000 claims description 3
- 230000005236 sound signal Effects 0.000 claims 3
- 238000010586 diagram Methods 0.000 description 7
- 230000000694 effects Effects 0.000 description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- 229910052799 carbon Inorganic materials 0.000 description 3
- 230000005540 biological transmission Effects 0.000 description 2
- 230000008901 benefit Effects 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 230000001627 detrimental effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
Description
【考案の詳細な説明】
本考案は電気音響変換器と増幅器とを用いた電
話送話器用増幅回路に関するものである。DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an amplifier circuit for a telephone transmitter using an electroacoustic transducer and an amplifier.
カーボン送話器は入出力特性に直線性がなく、
入力音圧があるレベルより小さくなると、出力は
より小さくなる性質を持つている。従つて、これ
を電話機用の送話器として用いた場合、音声入力
レベルと周囲騒音レベルとを比較すると、一般的
には周囲騒音レベルの方が小さいので、送話器に
音声入力がない場合には受話時の側音量が小さく
なり、相手からの通話音声が聞き易くなるという
防騒音効果がある。 Carbon transmitters have no linearity in input/output characteristics,
When the input sound pressure becomes lower than a certain level, the output becomes smaller. Therefore, when using this as a telephone transmitter, if you compare the voice input level and the ambient noise level, the ambient noise level is generally lower, so if the transmitter does not have an audio input has the noise-proofing effect of reducing the side volume when receiving a call, making it easier to hear the caller's voice.
しかしながら、カーボン送話器は直流供給電流
の多少によつて感度が変化することや、重くて大
きいなどの欠点がある。これに対し、送話器ユニ
ツトにセラミツクユニツトあるいはエレクトレツ
ト形マイクロホンユニツト等を用い、増幅器と組
合せ、小形軽量化をはかつた送話器がある。しか
し、このままであると入出力特性が線形であるた
めの前述の防騒音効果がない。このため増幅器に
音声スイツチング回路を設けて炭素送話器と同等
な効果を得ようとする回路構成がある。このよう
な音声スイツチング回路構成については昭和55年
６月19日に公告された実公昭55−25581号に記載
されている。 However, carbon transmitters have drawbacks such as sensitivity changes depending on the amount of DC supply current and that they are heavy and large. On the other hand, there are transmitters that use a ceramic unit or an electric microphone unit in the transmitter unit and combine it with an amplifier to reduce the size and weight. However, if left as is, the above-mentioned noise-proofing effect due to the linear input/output characteristics would not be achieved. For this reason, there is a circuit configuration in which an audio switching circuit is provided in the amplifier to obtain an effect equivalent to that of a carbon transmitter. Such an audio switching circuit configuration is described in Utility Model Publication No. 55-25581 published on June 19, 1981.
第１図はこの回路図であつて、送話器ユニツト
１の信号出力を前置増幅回路２で増幅し、主増幅
器４に加える。ここで増幅された信号は極性を合
わせるダイオードブリツジ５を通り、出力端子６
から出力される。前置増幅回路２の信号は音声ス
イツチング回路７にも加えられており、この回路
７は入力が閾値を越えた時に負帰還回路３の負帰
還量を少なくする様に働く。直流供給電流は出力
端子６から供給されるが、極性が反転しても電気
回路に供給される極性が変化しない様にダイオー
ドブリツジ５が入つており、このダイオードブリ
ツジ５を通して主増幅器４に電流を供給してい
る。８は温度特性を特たせた定電圧電源回路であ
る。 FIG. 1 is a circuit diagram of this circuit, in which the signal output of the transmitter unit 1 is amplified by a preamplifier circuit 2 and applied to a main amplifier 4. The amplified signal passes through a diode bridge 5 that matches the polarity, and then passes through an output terminal 6.
is output from. The signal from the preamplifier circuit 2 is also applied to an audio switching circuit 7, which operates to reduce the amount of negative feedback from the negative feedback circuit 3 when the input exceeds a threshold value. The DC supply current is supplied from the output terminal 6, but a diode bridge 5 is included so that the polarity supplied to the electric circuit does not change even if the polarity is reversed. It supplies current. 8 is a constant voltage power supply circuit with special temperature characteristics.
この回路における入出力特性は、電話機の所要
周波数帯域（300〜3400Hz）で周波数に関係なく
第２図の様になる。音声スイツチの入力動作レベ
ルは、一般的標準送話入力音圧（94dBSPL）よ
り10〜15dB低いレベルに設定しており、このよ
うな入出力特性では一般的に騒音は低周波数に分
布しているため防騒音効果が少ない欠点がある。
一般的標準送話入力音圧（94dBSPL）より５〜
10dB低い所に音声スイツチの入力動作レベルを
設定すると、防騒音効果はよくなるが、反面通話
中音声が少しでも小さくなると、周波数帯域全般
に亘つて音声途切れが発生し、送話に対し自然性
が著しく損われる欠点がある。 The input/output characteristics of this circuit are as shown in FIG. 2 in the required frequency band of the telephone (300 to 3400 Hz) regardless of the frequency. The input operating level of the audio switch is set to a level 10 to 15 dB lower than the general standard transmitting input sound pressure (94 dBSPL), and with such input/output characteristics, noise is generally distributed in low frequencies. Therefore, it has the disadvantage of having little noise-proofing effect.
5~ from the general standard voice input sound pressure (94dBSPL)
Setting the input operating level of the audio switch 10 dB lower will improve the noise reduction effect, but on the other hand, if the voice during a call becomes even a little low, audio interruptions will occur throughout the frequency band, making the transmission sound less natural. There are some drawbacks that are seriously detrimental.
本考案は、この欠点を途去するために、前置増
幅器の出力レベルが予め定めた閾値を越えたとき
音声スイツチング回路によつて主増幅器の負帰還
量を周波数に応じて変化させる事により、防騒音
効果を得ることができる電話送話用増幅回路を提
供するものである。 In order to eliminate this drawback, the present invention uses an audio switching circuit to change the amount of negative feedback of the main amplifier according to the frequency when the output level of the preamplifier exceeds a predetermined threshold. An object of the present invention is to provide an amplifier circuit for telephone transmission that can obtain a noise-proofing effect.
以下図面を用いて本考案を詳細に説明する。 The present invention will be explained in detail below using the drawings.
第３図は本考案の具体的回路例であり、第３−
１図は本考案の負帰還回路の他の実施例である。
第４図は本考案の回路による入出力特性である。 Figure 3 shows a specific example of the circuit of the present invention.
FIG. 1 shows another embodiment of the negative feedback circuit of the present invention.
FIG. 4 shows the input/output characteristics of the circuit of the present invention.
第３図の回路において、イはインピーダンス変
換器を含んだ送話器とバイアス回路を有する送話
器出力回路であり、送話器の出力信号は結合コン
デンサC2を通して前置増幅器ロで増幅され、主
増幅器ニに加えられる。増幅された信号は極性を
合わせるダイオードブリツジホを通り、出力端子
ヘから出て行く。前置増幅器ロの信号は音声スイ
ツチング回路トにも加えられており、この音声ス
イツチング回路トは入力が閾値を超えたときに負
帰還回路ハの負帰還量を少なくする様に働く。直
流電流は出力端子ヘから供給され、ダイオードブ
リツジホを通して主増幅器ニ及び温度特性を特た
せた定電圧電源回路チに加えられ、この定電圧電
源回路チを通して定電圧化された電源が前置増幅
器ロ及び音声スイツチング回路トに加えられる。 In the circuit shown in Figure 3, A is a transmitter output circuit having a transmitter including an impedance converter and a bias circuit, and the output signal of the transmitter is amplified by a preamplifier B through a coupling capacitor C2 . , is added to the main amplifier D. The amplified signal passes through a polarity matching diode bridge and exits to the output terminal. The signal from the preamplifier B is also applied to an audio switching circuit G, which functions to reduce the amount of negative feedback from the negative feedback circuit C when the input exceeds a threshold value. Direct current is supplied from the output terminal and is applied through the diode bridge to the main amplifier (2) and constant voltage power supply circuit (2) with specified temperature characteristics, and through this constant voltage power supply circuit (1), a constant voltage power supply is connected to the front. Added to amplifier and audio switching circuit.
次にこの実施例の動作を詳細に説明する。主増
幅器ニの出力は負帰還回路ハによつて負帰還され
ている。負帰還回路ハの帰還インピーダンスは
R5とR4＋C3との並列接続で構成される。R4とC3
との接点はコンデンサC7とトランジスタQ6とを
通して交流的に接地できる様になつている。ま
ず、音声入力がない場合のバイアス状態はトラン
ジスタQ4が抵抗器R8によりオンの状態になつて
おり、そのためトランジスタQ6のベース電流は
流れず、R4とC3との接点と接地との間のインピ
ーダンスは大きい。従つて、主増幅器ニの帰還イ
ンピーダンスはR5とR4＋１／ωC3との並列の値であ
る。次に、音声入力が入つて音声スイツチの閾値
を越えた場合には、前置増幅器ロの負の半サイク
ルによりトランジスタQ4がオフの状態となる。
このとき次段のトランジスタQ5はオンの状態と
なり、コンデンサC6の電荷はほぼT1＝C6R11の時
定数で放電される。次の正の半サイクルでトラン
ジスタQ4はオンの状態となり、トランジスタQ5
はオフの状態となつてコンデンサC6はほぼT2＝
C6（R10＋R11）の時定数で充電を始める。ここ
で、T2はT1に比べて長く設定しておき、音声等
の入力が連続して入つてくる場合、コンデンサ
C6の電位はほぼ零に保たれる。よつてトランジ
スタQ6のベース電流が流れるため、R4とC3との
接点と接地との間のインピーダンスは小さくな
り、主増幅器ニの帰還抵抗はR5だけとなる。 Next, the operation of this embodiment will be explained in detail. The output of main amplifier D is negatively fed back by negative feedback circuit C. The feedback impedance of negative feedback circuit C is
Consists of parallel connection of R 5 and R 4 + C 3 . R4 and C3
The contact point between the two terminals can be grounded in an alternating current manner through a capacitor C7 and a transistor Q6 . First, in the bias state when there is no audio input, transistor Q 4 is turned on by resistor R 8 , so the base current of transistor Q 6 does not flow, and the contact between R 4 and C 3 is connected to ground. The impedance between them is large. Therefore, the feedback impedance of main amplifier D is the parallel value of R 5 and R 4 +1/ωC 3 . Next, when the audio input comes in and exceeds the audio switch threshold, the negative half cycle of preamplifier B turns transistor Q4 off.
At this time, the next stage transistor Q5 is turned on, and the charge in the capacitor C6 is discharged with a time constant of approximately T1 = C6R11 . In the next positive half cycle transistor Q 4 is on and transistor Q 5
is in the off state and capacitor C 6 is approximately T 2 =
Charging begins with a time constant of C 6 (R 10 + R 11 ). Here, T 2 should be set longer than T 1 , and if input such as audio comes in continuously, the capacitor
The potential of C 6 is kept near zero. Therefore, since the base current of transistor Q6 flows, the impedance between the contact point of R4 and C3 and the ground becomes small, and the feedback resistance of main amplifier D becomes only R5 .
上述のように、トランジスタQ6のスイツチン
グにより帰還抵抗が変化するので、入出力特性が
変化するとともに周波数の減少に応じて帰環イン
ピーダンスが変わるため、帰還量も減少するよう
に変化する。結合コンデンサC2の値を適当に選
ぶことにより、このコンデンサC2が送話器出力
回路イに直列に入つているため、前置増幅器ロか
らみた低周波入力が低い。一方、スイツチング回
路トの動作は一定レベルに設定するから、低周波
の入力レベルが大きくなければ動作しない。この
組合せによる入出力特性は第４図に示すような特
性となる。第４図でＡは1000Hz、Ｂは300Hzの入
出力特性例を示す。このＡとＢとの間に1000Hz〜
300Hzの中間の周波数の入出力特性が存在するこ
とになる。 As mentioned above, the switching of transistor Q6 changes the feedback resistance, so the input/output characteristics change, and the return impedance changes as the frequency decreases, so the amount of feedback also changes to decrease. By choosing the value of the coupling capacitor C 2 appropriately, the low frequency input seen from the preamplifier B is low because this capacitor C 2 is connected in series with the transmitter output circuit A. On the other hand, since the operation of the switching circuit is set to a constant level, it will not operate unless the low frequency input level is large. The input/output characteristics resulting from this combination are as shown in FIG. In Fig. 4, A shows an example of input/output characteristics at 1000Hz, and B shows an example of an input/output characteristic at 300Hz. 1000Hz~ between this A and B
There will be an input/output characteristic at an intermediate frequency of 300Hz.
負帰還回路ハは第３−１図のハ′のように構成
することもできる。 The negative feedback circuit C can also be configured as shown in C' in FIG. 3-1.
以上説明したように、本考案の回路構成をとれ
ば、低周波では入力レベルが高い位置でスイツチ
ング動作し、高い周波数では入力レベルが低い位
置でスイツチング動作する。さらに、低周波数で
は変化量を少なく、高い周波数で変化量が大きく
得られる。このような特性が得られるため、騒音
の多い個所で使用する送話増幅器として防騒音効
果が得られ、かつ、自然性が損われない利点があ
る。常時騒音の多い送話器、例えば、自動車用電
話機の送話器用増幅器に用いれば特に効果が大き
い。 As explained above, if the circuit configuration of the present invention is adopted, the switching operation is performed at a position where the input level is high at low frequencies, and the switching operation is performed at a position where the input level is low at high frequencies. Furthermore, a small amount of change can be obtained at low frequencies, and a large amount of change can be obtained at high frequencies. Since such characteristics can be obtained, the transmitting amplifier used in a noisy place has the advantage of providing a noise-proofing effect and not impairing its natural appearance. It is particularly effective when used in a transmitter that is constantly noisy, such as a transmitter amplifier for a car telephone.
第１図は従来例の回路構成図、第２図は従来回
路による入出力特性図、第３図は本考案の実施例
を示す回路図、第３−１図は本考案に用いる帰還
回路の他の例を示す回路図、第４図は本考案の入
出力特性図である。
イ……送話器出力回路、ロ……前置増幅器、ハ
……負帰還回路、ニ……主増幅器、ホダイオード
ブリツジ、ヘ……出力端子、ト……音声スイツチ
ング回路、チ……定電圧電源回路、C2……結合
コンデンサ。
Figure 1 is a circuit configuration diagram of a conventional example, Figure 2 is an input/output characteristic diagram of a conventional circuit, Figure 3 is a circuit diagram showing an embodiment of the present invention, and Figure 3-1 is a feedback circuit diagram used in the present invention. FIG. 4 is a circuit diagram showing another example, and is an input/output characteristic diagram of the present invention. A...Telephone output circuit, B...Preamplifier, C...Negative feedback circuit, D...Main amplifier, diode bridge, F...Output terminal, G...Audio switching circuit, CH... Constant voltage power supply circuit, C 2 ...coupling capacitor.
Claims (1)
ンサと、該結合コンデンサの出力の電気信号を増
幅する前置増幅器と、該前置増幅器の音声信号出
力を増幅する主増幅器と、該主増幅器の負帰還量
を変化できる負帰還回路と、前記前置増幅器の音
声信号出力が予め定めた閾値を越えた場合に前記
負帰還回路の負帰還量を周波数の減少に応じて所
要量だけ減少させるとともに前記閾値以下になつ
たときに再びその一定量だけ負帰還量を増加させ
て低い周波数では入力レベルが高い位置でスイツ
チング動作をし高い周波数では入力レベルが低い
位置でスイツチング動作をする音声スイツチング
回路と、前記前置増幅器と前記音声スイツチング
回路に所要の電力を供給する定電圧電源回路とを
備えた電話送話器用増幅回路。 A coupling capacitor inserted in series in a transmitter output circuit, a preamplifier that amplifies the electrical signal output from the coupling capacitor, a main amplifier that amplifies the audio signal output of the preamplifier, and a main amplifier that amplifies the audio signal output of the preamplifier. a negative feedback circuit that can change the amount of negative feedback; and when the audio signal output of the preamplifier exceeds a predetermined threshold, the amount of negative feedback of the negative feedback circuit is reduced by a required amount in accordance with a decrease in frequency; An audio switching circuit that increases the amount of negative feedback by a certain amount again when the value falls below the threshold value, and performs a switching operation at a position where the input level is high at low frequencies, and at a position where the input level is low at high frequencies. , an amplifier circuit for a telephone transmitter, comprising the preamplifier and a constant voltage power supply circuit for supplying necessary power to the audio switching circuit.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10884382U JPS5914439U (en) | 1982-07-20 | 1982-07-20 | Amplifier circuit for telephone handset |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP10884382U JPS5914439U (en) | 1982-07-20 | 1982-07-20 | Amplifier circuit for telephone handset |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS5914439U JPS5914439U (en) | 1984-01-28 |
| JPH026699Y2 true JPH026699Y2 (en) | 1990-02-19 |
Family
ID=30253780
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP10884382U Granted JPS5914439U (en) | 1982-07-20 | 1982-07-20 | Amplifier circuit for telephone handset |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS5914439U (en) |
-
1982
- 1982-07-20 JP JP10884382U patent/JPS5914439U/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS5914439U (en) | 1984-01-28 |
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