JPH0217706A - Variable gain amplifier circuit - Google Patents
Variable gain amplifier circuitInfo
- Publication number
- JPH0217706A JPH0217706A JP16682988A JP16682988A JPH0217706A JP H0217706 A JPH0217706 A JP H0217706A JP 16682988 A JP16682988 A JP 16682988A JP 16682988 A JP16682988 A JP 16682988A JP H0217706 A JPH0217706 A JP H0217706A
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- JP
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- Prior art keywords
- resistor
- slider
- feedback
- terminal
- amplifier
- 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.)
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- 230000002542 deteriorative effect Effects 0.000 description 5
- 238000010586 diagram Methods 0.000 description 5
- 230000003321 amplification Effects 0.000 description 3
- 238000003199 nucleic acid amplification method Methods 0.000 description 3
- 230000006866 deterioration Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
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- Control Of Amplification And Gain Control (AREA)
Abstract
Description
【発明の詳細な説明】
〔産業上の利用分野〕
本発明は、オーディオ増幅器に用いて好適な可変利得増
幅回路に関し、特に可変抵抗器の摺動子に信号電流が流
れることに寄囚する摺動子の接点の劣化を防止した可変
利得増幅回路に関する。[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a variable gain amplification circuit suitable for use in an audio amplifier, and particularly to a variable gain amplification circuit suitable for use in an audio amplifier. The present invention relates to a variable gain amplification circuit that prevents deterioration of contacts of an actuator.
本発明は、オーディオ増幅器に用いて好適な入力端子、
帰還端子及び出力端子を有する帰還増幅器を用いた可変
利得増幅回路において、第１の抵抗器、摺動子を有する
可変抵抗器及び第２の抵抗器から成る直列回路と、第３
の抵抗器とを設け、前記直列回路を前記帰還増幅器の出
力端子と基準電位との間に接続し、前記第３の抵抗器を
前記帰還増幅器の帰還端子と、前記直列回路の第１の抵
抗器と可変抵抗器の接続点との間に接続し、前記可変抵
抗器の摺動子を前記帰還増幅器の帰還端子に接続するこ
とにより、前記摺動子に信号電流が流れることを阻止し
、摺動子の接点の劣化を防止することができる。The present invention provides an input terminal suitable for use in an audio amplifier;
In a variable gain amplifier circuit using a feedback amplifier having a feedback terminal and an output terminal, the series circuit includes a first resistor, a variable resistor having a slider, and a second resistor, and a third resistor.
a resistor, the series circuit is connected between the output terminal of the feedback amplifier and a reference potential, and the third resistor is connected between the feedback terminal of the feedback amplifier and the first resistor of the series circuit. connecting between the variable resistor and the connection point of the variable resistor, and connecting the slider of the variable resistor to the feedback terminal of the feedback amplifier to prevent a signal current from flowing through the slider; Deterioration of the contacts of the slider can be prevented.
従来の可変利得増幅回路の一例として、例えば第３図に
示すように、帰還用抵抗器の一方に可変抵抗器を用いた
可変利得増幅回路が知られている。。As an example of a conventional variable gain amplifier circuit, for example, as shown in FIG. 3, a variable gain amplifier circuit using a variable resistor as one of the feedback resistors is known. .
すなわち、第３図において、１は帰還増幅器で、入力端
子２、帰還端子３及び出力端子４を有し、出力端子４と
帰還端子３の間に帰還抵抗器５が接続され、帰還端子３
と基準電位との間に摺動子６ａを有する可変抵抗器６と
抵抗器７が直列に接続され、可変抵抗器６の摺動子６ａ
を操作することにより、出力端子４の出力信号のレベル
を可変することができる。この場合、可変抵抗器６を固
定抵抗器とし、帰還抵抗器５を可変型抵抗器で構成して
も同等の動作が可能である。That is, in FIG. 3, 1 is a feedback amplifier, which has an input terminal 2, a feedback terminal 3, and an output terminal 4. A feedback resistor 5 is connected between the output terminal 4 and the feedback terminal 3.
A variable resistor 6 and a resistor 7 having a slider 6a between the variable resistor 6 and a reference potential are connected in series, and the slider 6a of the variable resistor 6
By operating the output terminal 4, the level of the output signal of the output terminal 4 can be varied. In this case, the same operation is possible even if the variable resistor 6 is a fixed resistor and the feedback resistor 5 is a variable resistor.
また、従来の可変利得増幅回路の他の例として、第４図
に示す如く、帰還増幅器の出力側に可変抵抗器を設けた
可変利得増幅回路が知られている（特開昭５６−１０６
４０６号公報参照）。Further, as another example of the conventional variable gain amplifier circuit, a variable gain amplifier circuit is known in which a variable resistor is provided on the output side of a feedback amplifier, as shown in FIG.
(See Publication No. 406).
すなわち、第４図において、９は第１の電圧／電流変換
器で、入力端子１０に供給される電圧を電流に変換し、
出力端子１１に電流出力を供給する。That is, in FIG. 4, 9 is a first voltage/current converter that converts the voltage supplied to the input terminal 10 into a current,
A current output is supplied to the output terminal 11.
１２は第２の電圧／電流変換器で、入力端子１３に供給
される電圧を電流に変換し、出力端子１４に電流出力を
供給する。１５は入力セレクターで、出力端子１１また
は出力端子１４の電流出力を選択して摺動子６ａを有す
る可変抵抗器６に供給し、可変抵抗器６の両端に電流／
電圧変換された信号を発生する。従って、パワーアンプ
１６の出力端子１６ａの電圧は、可変抵抗器６の摺動子
６ａを調整することにより、利得制御される。A second voltage/current converter 12 converts the voltage supplied to the input terminal 13 into a current, and supplies a current output to the output terminal 14. 15 is an input selector which selects the current output of the output terminal 11 or the output terminal 14 and supplies it to the variable resistor 6 having a slider 6a, so that the current /
Generates a voltage-converted signal. Therefore, the voltage at the output terminal 16a of the power amplifier 16 is gain controlled by adjusting the slider 6a of the variable resistor 6.
しかしながら、前者のものにおいては、帰還増幅器１の
帰還端子３の電圧が可変抵抗器６に印加され、摺動子６
ａに信号電流が流れるため、摺動子６ａの接点が劣化す
るおそれがあった。However, in the former case, the voltage at the feedback terminal 3 of the feedback amplifier 1 is applied to the variable resistor 6, and the slider 6
Since the signal current flows through a, there is a risk that the contacts of the slider 6a may deteriorate.
また、前記抵抗器５に可変抵抗器を用いた場合にも、出
力端子４の電圧と帰還端子３の電圧との差の電圧により
、摺動子６ａに信号電流が流れるため、同様の欠点があ
った。Further, even when a variable resistor is used as the resistor 5, a signal current flows through the slider 6a due to the voltage difference between the voltage at the output terminal 4 and the voltage at the feedback terminal 3, so a similar drawback occurs. there were.
更に、後者の如く段間に摺動子６ａを有する可変抵抗器
６を設けるものは、出力端子１１または出力端子１４の
信号電流が可変抵抗器６の摺動子６ａに流れ、摺動子６
ａの接点が劣化するおそれがあった。Furthermore, in the latter case where the variable resistor 6 is provided with a slider 6a between stages, the signal current of the output terminal 11 or the output terminal 14 flows to the slider 6a of the variable resistor 6, and the slider 6
There was a risk that the contact point a would deteriorate.
従って、本発明の目的は前記欠点を改良した可変利得増
幅回路を提供することにある。SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a variable gain amplifier circuit that improves the above-mentioned drawbacks.
本発明の可変利得増幅回路は、入力端子、帰還端子及び
出力端子を有する帰還増幅器を用いた可変利得増幅回路
において、第１の抵抗器、摺動子を有する可変抵抗器及
び第２の抵抗器から成る直列回路と、第３の抵抗器とを
設け、前記直列回路を前記帰還増幅器の出力端子と基準
電位との間に接続し、前記第３の抵抗器を前記帰還増幅
器の帰還端子と、前記直列回路の第１の抵抗器と可変抵
抗器の接続点との間に接続し、前記可変抵抗器の摺動子
を前記帰還増幅器の帰還端子に接続して構成される。The variable gain amplifier circuit of the present invention is a variable gain amplifier circuit using a feedback amplifier having an input terminal, a feedback terminal, and an output terminal. and a third resistor, the series circuit is connected between the output terminal of the feedback amplifier and a reference potential, and the third resistor is connected to the feedback terminal of the feedback amplifier, It is connected between a connection point of the first resistor of the series circuit and a variable resistor, and a slider of the variable resistor is connected to a feedback terminal of the feedback amplifier.
前記構成によれば、第３の抵抗器の両端の電圧は略一定
になり、可変抵抗器の摺動子に信号電流が流れないので
、摺動子の接点が劣化するおそれがない。また、摺動子
の接点が振動等により浮いてしまった場合にも、第３の
抵抗器による帰還ループが構成されるので、出力端子に
雑音を生じることがない。According to the above configuration, the voltage across the third resistor becomes substantially constant, and no signal current flows through the slider of the variable resistor, so there is no risk of the contacts of the slider deteriorating. Further, even if the contacts of the slider are lifted due to vibration or the like, since a feedback loop is formed by the third resistor, no noise is generated at the output terminal.
以下、本発明の一実施例について、図面を参照して説明
する。An embodiment of the present invention will be described below with reference to the drawings.
第１図は本発明の可変利得増幅回路の基本構成を示すも
ので、従来例に対応する部分には同一番号を付してその
詳細な説明は省略する。FIG. 1 shows the basic configuration of a variable gain amplifier circuit according to the present invention, and parts corresponding to the conventional example are given the same reference numerals and detailed explanation thereof will be omitted.
第１図において、１８は第１の抵抗器、１９は摺動子１
９ａを有する可変抵抗器、２ｏは第２の抵抗器を示し、
第１の抵抗器１８、可変抵抗器１９及び第２の抵抗器２
０から成る直列回路２１は、帰還増幅器ｌの出力端子４
と基準電位との間に接続される。２２は第３の抵抗器を
示し、この第３の抵抗器２２は、帰還増幅器１の帰還端
子３と、第１の抵抗器１８と可変抵抗器１９の接続点と
の間に接続される。前記可変抵抗器１９の摺動子１９ａ
は帰還増幅器１の帰還端子３に接続される。In FIG. 1, 18 is the first resistor, 19 is the slider 1
a variable resistor with 9a, 2o indicates a second resistor;
First resistor 18, variable resistor 19 and second resistor 2
The series circuit 21 consisting of 0 is connected to the output terminal 4 of the feedback amplifier l.
and a reference potential. 22 indicates a third resistor, and this third resistor 22 is connected between the feedback terminal 3 of the feedback amplifier 1 and the connection point between the first resistor 18 and the variable resistor 19. Slider 19a of the variable resistor 19
is connected to the feedback terminal 3 of the feedback amplifier 1.
次に、前記構成における動作について説明する。Next, the operation in the above configuration will be explained.
第１の抵抗器１８、第２の抵抗器２０、第３の抵抗器２
２及び可変抵抗器１９の各抵抗値をそれぞれＲ＋、Ｒｔ
ＳＲｙ及びＲｖとして、Ｒ，）Ｒ，、Ｒ，＞Ｒｚ、Ｒ３
＞Ｒｖに選定すると、通常状態では、第３の抵抗器２２
は第１の抵抗器１日、第２の抵抗器２０及び可変抵抗器
１９より充分大きいため無視でき還増幅器ｌの帰還端子
３に流入するバイアス電流が流れるが、前述の従来例の
ものに比べ充分小さく、摺動子１９ａの接点（図示しな
い）を劣化するおそれがない。First resistor 18, second resistor 20, third resistor 2
2 and variable resistor 19 are R+ and Rt, respectively.
As SRy and Rv, R,)R,,R,>Rz,R3
>Rv, under normal conditions, the third resistor 22
is sufficiently larger than the second resistor 20 and the variable resistor 19, so it can be ignored, and a bias current flows into the feedback terminal 3 of the feedback amplifier 1, but compared to the conventional example described above, It is sufficiently small and there is no risk of deteriorating the contacts (not shown) of the slider 19a.
また、振動等の原因により摺動子１９ａの接点が浮いた
場合、帰還増幅器１の利得は前述した最小Ｐ。Furthermore, if the contact point of the slider 19a floats due to a cause such as vibration, the gain of the feedback amplifier 1 will be the minimum P as described above.
次に、本発明をオーディオ増幅器のプリアンプに適用し
た一実施例について、第２図を参照して説明する。Next, an embodiment in which the present invention is applied to a preamplifier of an audio amplifier will be described with reference to FIG.
第２図において、従来例を示す第４図に対応する部分に
は、同一番号を付してその詳細な説明は省略する。２３
は入力端子１ｏに供給される入力信号を電圧増幅する第
１の帰還増幅器（例えばイコライザアンプ）、２４は入
力端子１３に供給される入力信号を電圧増幅する第２の
帰還増幅器（例えばマイクアンプ）である、この第１の
帰還増幅器２３及び第２の帰還増幅器２４の出力は入力
セレクタ−１５によりいずれか一方が選択され、帰還増
幅器１の入力端子２に印加され、可変抵抗器１９の摺動
子１９ａの位置を可変することにより、利得制御が行わ
れる。この利得制御された出力端子４の信号は、パワー
アンプ１Ｇにより電力増幅され、パワーアンプの出力端
子１６ａから図示しないスピーカに供給される。この第
２図の実施例においても、可変抵抗器１９の摺動子１９
ａの位置に応じて前述した最小利得から最大利得の間で
利得制御が可能である。In FIG. 2, parts corresponding to those in FIG. 4 showing the conventional example are given the same numbers and detailed explanation thereof will be omitted. 23
24 is a first feedback amplifier (for example, an equalizer amplifier) that voltage-amplifies the input signal supplied to the input terminal 1o, and 24 is a second feedback amplifier (for example, a microphone amplifier) that voltage-amplifies the input signal supplied to the input terminal 13. One of the outputs of the first feedback amplifier 23 and the second feedback amplifier 24 is selected by the input selector 15 and applied to the input terminal 2 of the feedback amplifier 1, and the sliding of the variable resistor 19 is applied to the input terminal 2 of the feedback amplifier 1. Gain control is performed by varying the position of the child 19a. This gain-controlled signal at the output terminal 4 is power amplified by the power amplifier 1G, and is supplied to a speaker (not shown) from the output terminal 16a of the power amplifier. In the embodiment shown in FIG. 2 as well, the slider 19 of the variable resistor 19
Gain control is possible between the aforementioned minimum gain and maximum gain depending on the position of a.
また、通常状態において、可変抵抗器１９の摺動子１９
ａには帰還端子３に流入するバイアス電流だけが流れる
ので、摺動子１９ａの接点を劣化するおそれがないと同
時に、摺動子１９ａが浮いた場合には、帰還増幅器１は
最小利得になるので、スピーカから大出力の雑音を発生
することがない。Further, in the normal state, the slider 19 of the variable resistor 19
Since only the bias current flowing into the feedback terminal 3 flows through a, there is no risk of deteriorating the contacts of the slider 19a, and at the same time, if the slider 19a floats, the feedback amplifier 1 has the minimum gain. Therefore, high output noise is not generated from the speaker.
なお、前記帰還増幅器１は入力インピーダンスが高いの
で、バッファ回路も兼ねている。Note that since the feedback amplifier 1 has a high input impedance, it also serves as a buffer circuit.
以上の説明から明らかな通り、本発明の可変利得増幅回
路は、入力端子２、帰還端子３及び出力端子４を有する
帰還増幅器ｌを用いた可変利得増幅回路において、第１
の抵抗器１８、摺動子１９ａを有する可変抵抗器１９及
び第２の抵抗器２０から成る直列回路２１と、第３の抵
抗器２２とを設け、前記直列回路２工を前記帰還増幅器
ｌの出力端子４と基準電位との間に接続し、前記第３の
抵抗ａ２２を前記帰還増幅器Ｉの帰還端子３と、前記直
列回路２１の第１の抵抗ｎ１８と可変抵抗器１９の接続
点との間に接続し、前記可変抵抗農工９の摺動子１９ａ
を前記帰還増幅器１の帰還端子３に接続して構成するこ
とにより、摺動子９ａの接点の劣化を防止できると共に
、出力端子４に雑音を発生するおそれがない。As is clear from the above description, the variable gain amplifier circuit of the present invention uses a feedback amplifier l having an input terminal 2, a feedback terminal 3, and an output terminal 4.
A series circuit 21 consisting of a resistor 18, a variable resistor 19 having a slider 19a, and a second resistor 20, and a third resistor 22 are provided, and the series circuit 2 is connected to the feedback amplifier l. The third resistor a22 is connected between the output terminal 4 and the reference potential, and the connection point between the feedback terminal 3 of the feedback amplifier I, the first resistor n18 of the series circuit 21, and the variable resistor 19. the slider 19a of the variable resistance agricultural machinery 9;
By connecting this to the feedback terminal 3 of the feedback amplifier 1, it is possible to prevent the contacts of the slider 9a from deteriorating, and there is no risk of generating noise at the output terminal 4.
なお、上述の実施例においては、本発明をオーディオ増
幅器のプリアンプに適用した場合について述べたが、テ
ープレコーダの記録または再生回路等、他の増幅回路に
適用することができる。In the above-described embodiments, the present invention was applied to a preamplifier of an audio amplifier, but it can also be applied to other amplifier circuits such as a recording or reproducing circuit of a tape recorder.
本発明によれば、可変抵抗器の摺動子に信号電流が流れ
ないように構成したので、摺動子の接点の劣化を防止す
ることができる。According to the present invention, since the configuration is such that no signal current flows through the slider of the variable resistor, it is possible to prevent the contacts of the slider from deteriorating.
また、振動等により可変抵抗器の摺動子が浮いた場合に
も、第３の抵抗器を設けたので、帰還増幅器の出力端子
に大出力の雑音を発生ずるおそれがない。Furthermore, even if the slider of the variable resistor floats due to vibration or the like, since the third resistor is provided, there is no risk of generating large output noise at the output terminal of the feedback amplifier.
第１図は本発明の可変利得増幅回路の基本構成を示す接
続図、第２図は本発明の可変利得増幅回路の一実施例を
示すブロック図、第３図は従来の可変利得増幅回路の一
例を示す接続図、第４図は従来の可変利得増幅回路の他
の例を示すブロック図である。
ｌ−・−・−・・−帰還増幅器
２・・−・−・・・・−・入力端子
３−・−・−・−帰還端子
４・−・−・・・・−出力端子
６・−・・−・・−・−・−可変抵抗器９−・−・−・
・−・・−第１の電圧／電流変換器１２・・・・−・・
・・・−第２の電圧／電流変換器１５・・・−・・・−
・−・入力セレクター１６・・・−・・・・−・−・パ
ワーアンプ１８−・−・−ｍ−−−・−−−−一第１の
抵抗器１９・−・−・−・・・・−可変抵抗器１９ａ−
・・・−・・・・−摺動子
２（Ｌ−−−−・・・−・−・・−第２の抵抗器■・−
・・・−・−・・−・−直列回路２２・・・・・−・−
・・・・−・第３の抵抗器２３・・−・・・−・・・−
・・−第１の帰還増幅器２４・−一−−−・・−・−・
−・第２の帰還増幅器本会明の可変利得増幅回路の墓本
橋成
第１図
従来の可変利得増幅回路の一例
第３図
本発明の可変利１斗増幅回路め一実檄列第２図
従来の可変利得増幅回路め他のイｌす
第４図FIG. 1 is a connection diagram showing the basic configuration of the variable gain amplifier circuit of the present invention, FIG. 2 is a block diagram showing an embodiment of the variable gain amplifier circuit of the present invention, and FIG. 3 is a diagram of the conventional variable gain amplifier circuit. A connection diagram showing one example, and FIG. 4 is a block diagram showing another example of a conventional variable gain amplifier circuit. l-・-・−・・−Feedback amplifier 2・・−・−・・・・Input terminal 3−・−・−・−Feedback terminal 4・−・−・・−Output terminal 6・−・・−・・−・−・−Variable resistor 9−・−・−・
・-・・-First voltage/current converter 12 ・・・・・・
...-Second voltage/current converter 15...--
・−・Input selector 16・−・・・−・−・Power amplifier 18−・−・−m−−−・−−−−1st resistor 19・−・−・−・・...-variable resistor 19a-
・・・−・・−Slider 2 (L−−−−・−・−・・−Second resistor ■・−
・・・−・−・・−・−Series circuit 22・・・・・−・−
......-Third resistor 23...-...-
...-first feedback amplifier 24.--1---.--
-Second Feedback Amplifier Grave of the variable gain amplifier circuit of the present inventionNari Motohashi Figure 1 An example of a conventional variable gain amplifier circuit Figure 3 Variable gain amplifier circuit of the present invention Meichiji's series Figure 2 Figure 4 shows another example of the conventional variable gain amplifier circuit.
Claims (1)
用いた可変利得増幅回路において、第１の抵抗器、摺動
子を有する可変抵抗器及び第２の抵抗器から成る直列回
路と、第３の抵抗器とを設け、前記直列回路を前記帰還
増幅器の出力端子と基準電位との間に接続し、前記第３
の抵抗器を前記帰還増幅器の帰還端子と、前記直列回路
の第１の抵抗器と可変抵抗器の接続点との間に接続し、
前記可変抵抗器の摺動子を前記帰還増幅器の帰還端子に
接続したことを特徴とする可変利得増幅回路。In a variable gain amplifier circuit using a feedback amplifier having an input terminal, a feedback terminal, and an output terminal, the series circuit includes a first resistor, a variable resistor having a slider, and a second resistor, and a third resistor. a resistor, the series circuit is connected between the output terminal of the feedback amplifier and a reference potential, and the third
A resistor is connected between the feedback terminal of the feedback amplifier and a connection point between the first resistor and the variable resistor of the series circuit,
A variable gain amplifier circuit characterized in that a slider of the variable resistor is connected to a feedback terminal of the feedback amplifier.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16682988A JPH0217706A (en) | 1988-07-06 | 1988-07-06 | Variable gain amplifier circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP16682988A JPH0217706A (en) | 1988-07-06 | 1988-07-06 | Variable gain amplifier circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH0217706A true JPH0217706A (en) | 1990-01-22 |
Family
ID=15838432
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP16682988A Pending JPH0217706A (en) | 1988-07-06 | 1988-07-06 | Variable gain amplifier circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH0217706A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003008375A (en) * | 2001-06-21 | 2003-01-10 | Asahi Kasei Microsystems Kk | Variable gain amplifier |
-
1988
- 1988-07-06 JP JP16682988A patent/JPH0217706A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2003008375A (en) * | 2001-06-21 | 2003-01-10 | Asahi Kasei Microsystems Kk | Variable gain amplifier |
| JP4708604B2 (en) * | 2001-06-21 | 2011-06-22 | 旭化成エレクトロニクス株式会社 | Variable gain amplifier |
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