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
- Japan
- 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.)
- Pending
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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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