JP3460040B2 - Amplifier circuit - Google Patents
Amplifier circuitInfo
- Publication number
- JP3460040B2 JP3460040B2 JP18596497A JP18596497A JP3460040B2 JP 3460040 B2 JP3460040 B2 JP 3460040B2 JP 18596497 A JP18596497 A JP 18596497A JP 18596497 A JP18596497 A JP 18596497A JP 3460040 B2 JP3460040 B2 JP 3460040B2
- Authority
- JP
- Japan
- Prior art keywords
- voltage
- amplification stage
- stage
- power
- output voltage
- 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 - Fee Related
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- Amplifiers (AREA)
Description
【発明の詳細な説明】
【０００１】
【発明の属する技術分野】本発明は、増幅回路に関し、
さらに詳細には電力増幅段の出力電圧を選択的に負帰還
する増幅回路に関する。
【０００２】
【従来の技術】従来の増幅回路は図２に示すように構成
されている。図２に示す増幅回路は電圧増幅段１１１の
出力電圧をコンプリメンタリに接続されたトランジスタ
１２１と１２２とからなる電力増幅段１１２に供給して
電力増幅してスピーカなどの負荷を駆動し、電圧増幅段
１１１からの出力電圧と電力増幅段１１２の出力電圧と
を切り換えスイッチ１１３によって一方を選択して電圧
増幅段１１１へ負帰還するように構成されている。
【０００３】
【発明が解決しようとする課題】このような従来に増幅
回路において、切り換えスイッチ１１３によって電力増
幅段１１２の出力電圧を負帰還したときはクリップ時や
高い周波数で電圧増幅段１１１と電力増幅段１１２の周
波数特性の違いによって帰還がかからないためオーディ
オ増幅器とした場合、音質が悪化するという問題点があ
った。また、切り換えスイッチ１１３によって電圧増幅
段１１１の出力電圧を選択して負帰還した場合は、増幅
回路の出力信号の歪が残留して歪が除去できないという
問題点があった。
【０００４】本発明は、歪の増加を抑制した増幅回路を
提供することを目的とする。
【０００５】
【０００６】
【０００７】【課題を解決するための手段】
本発明の増幅回路は、電
圧増幅段と該電圧増幅段の出力電圧によって駆動される
電力増幅段とを備えた増幅回路において、電圧増幅段の
出力電圧の交流成分を電圧増幅段へ負帰還させるか電力
増幅段の出力電圧の交流成分を電圧増幅段へ負帰還させ
るかの何れか一方を選択する選択手段と、選択手段によ
って電圧増幅段の出力電圧の交流成分を電圧増幅段へ負
帰還することを選択したとき電力増幅段をＡ級動作さ
せ、かつ選択手段によって電力増幅段の出力電圧の交流
成分を電圧増幅段へ負帰還することを選択したとき電力
増幅段をＡＢ級またはＢ級動作させる切り換え手段とを
備えたことを特徴とする。
【０００８】本発明の増幅回路によれば、選択手段によ
って電圧増幅段の出力電圧の交流成分を電圧増幅段へ負
帰還することを選択したときは、電圧増幅段の出力電圧
の交流成分が電圧増幅段へ負帰還され、かつ電力増幅段
がＡ級動作させられるため、オーディオ増幅器としたと
き帰還がかからないために音質は悪化することはなく、
音質は向上し、かつ電力増幅段はＡ級動作をしているた
め、増幅回路の出力信号の歪が低減される。選択手段に
よって電力増幅段の出力電圧の交流成分を電圧増幅段へ
負帰還することを選択したときは、電力増幅段の出力電
圧の交流成分が電圧増幅段へ負帰還されるため、オーデ
ィオ増幅器としたとき電力増幅段がＡＢ級またはＢ級動
作をさせられて、電力効率は向上させられる。
【０００９】
【発明の実施の形態】本発明にかかる増幅回路を実施の
一形態によって説明する。図１は本発明の実施の一形態
にかかる増幅回路の構成を示すブロック図である。
【００１０】本発明の実施の一形態にかかる増幅回路
は、電圧増幅段１の出力電圧は切り換えスイッチ１３を
通して選択的に抵抗１４を介して電圧増幅段１に負帰還
するように構成し、電圧増幅段１の出力電圧は電力増幅
段２に供給して電力増幅段２を駆動する。
【００１１】電力増幅段２はダーリントン接続のトラン
ジスタ１６と１８と、ダーリントン接続のトランジスタ
１７と１９とのシングルエンデッドプッシュプル増幅器
３と、ダイオード２１、２２、抵抗２３、２４、抵抗２
３に並列に接続されたスイッチ２５、抵抗２４に並列接
続された調整用の半固定抵抗２６とからなるバイアス回
路４とを備え、電力増幅段２の出力電圧の直流成分を抵
抗２７、コンデンサ２９および抵抗２８を介して電圧増
幅段１へ負帰還すると共に、電力増幅段２の出力電圧の
交流成分を切り換えスイッチ１３を通して抵抗１４を介
して電圧増幅段１に負帰還するように構成してある。
【００１２】ここで、切り換えスイッチ１３とスイッチ
２５とは切り換え信号によって連動して切り換えられ、
切り換えスイッチ１３によって電圧増幅段１の出力を負
帰還するように切り換えたときはスイッチ２５は開放状
態に切り換えられて電力増幅段２のバイアス電流をＡ級
動作の電流値に設定してアイドル電流を増加させ、切り
換えスイッチ１３によって電力増幅段２の出力電圧を負
帰還するように切り換えたときはスイッチ２５は閉成状
態に切り換えられて電力増幅段２のバイアス電流をＡＢ
級動作の電流値に設定してアイドル電流を減少させるよ
うに構成してある。
【００１３】上記のように構成された本発明の実施の一
形態にかかる増幅回路において、入力信号は電圧増幅段
１によって電圧増幅され、電圧増幅段１の出力信号は電
力増幅段２によって電力増幅される。
【００１４】切り換え信号に基づいて切り換えスイッチ
１３の共通接点を接点ａ側に切り換えると、スイッチ２
５は開放状態に切り換えられる。そこで、スイッチ２５
は開放されているため電力増幅段２のバイアス電流はＡ
級動作のバイアス電流値に設定され、電力増幅段２のア
イドル電流は増加させられる。一方、電圧増幅段１の出
力電圧は抵抗１４を介してコンデンサ１５を通して電圧
増幅段１に負帰還される。
【００１５】この場合、電力増幅段２の出力電圧の交流
成分は電圧増幅段１に負帰還されないため、帰還はずれ
は起こらず、かつ電力増幅段２のアイドル電流が増加さ
せられているために、電力増幅段２の出力信号の歪は少
なくてすむ。また、一方、電力増幅段２の出力電圧は抵
抗２７、コンデンサ２９および抵抗２８を介して直流的
に負帰還されて電力増幅段２の出力電圧の直流電圧の変
動が抑制される。
【００１６】切り換え信号に基づいて切り換えスイッチ
１３の共通接点が接点ｂ側に切り換えると、スイッチ２
５は閉成状態に切り換えられる。そこで、スイッチ２５
は閉成されているため電力増幅段２のバイアス電流はＡ
Ｂ級動作のバイアス電流値に設定され、電力増幅段２の
アイドル電流は減少させられる。一方、電力増幅段２の
出力電圧の直流成分は抵抗２７、コンデンサ２９および
抵抗２８を介して電圧増幅段１に負帰還され、かつ電力
増幅段２の出力電圧の交流成分は抵抗１４を介してコン
デンサ１５を通して電圧増幅段１に負帰還される。
【００１７】この場合、電力増幅段２の出力電圧の交流
成分は電圧増幅段１に負帰還されるために、帰還がかか
らない状態が発生する可能性は残るが、電力増幅段２の
アイドル電流が減少させられているために、電力増幅段
２の電力効率は改善されることになる。
【００１８】したがって、オーディオ増幅器とした場
合、音質を重視するときは切り換えスイッチ１３によっ
て電圧増幅段１の出力電圧を電圧増幅段１に負帰還する
べく選択し、電力効率を重視するときは切り換えスイッ
チ１３によって電力増幅段２の出力電圧を電圧増幅段１
に負帰還するべく選択することができて、使用者の選択
の幅が広がることになる
【００１９】本発明の実施の一形態にかかる増幅回路に
おいて、切替スイッチ１３およびスイッチ２５を設け
て、電圧増幅段の出力電圧を電圧増幅段へ負帰還しかつ
電圧増幅段をＡ級動作させるか、電力増幅段の出力電圧
を電圧増幅段へ負帰還しかつ電力増幅段をＡＢ級動作さ
せるかを選択するように構成した場合を例示したが、電
圧増幅段の出力電圧を電圧増幅段へ負帰還しかつ電力増
幅段をＡ級動作させるようにのみにして、選択のための
スイッチなどを省略してもよい。
【００２０】また、電力増幅段の出力電圧を電圧増幅段
へ負帰還した場合、電力増幅段をＢ級動作としてもよ
い。
【００２１】
【００２２】【発明の効果】
以上説明したように本発明の増幅回路に
よれば、電圧増幅段の出力電圧の交流成分を電圧増幅段
へ負帰還することを選択したときは、電圧増幅段の出力
電圧の交流成分が電圧増幅段へ負帰還され、電力増幅段
がＡ級動作させられるため、帰還はずれは起こらず、か
つ増幅回路の出力信号の歪が低減され、電力増幅段の出
力電圧の交流成分を電圧増幅段へ負帰還することを選択
したときは、帰還はずれが起こる可能性はあるが、電力
増幅段がＡＢ級またはＢ級動作をしているため、電力効
率が向上するという効果が得られ、選択の幅が増加する
という効果も得られる。Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an amplifier circuit,
More specifically, the present invention relates to an amplifier circuit that selectively negatively feedbacks an output voltage of a power amplification stage. 2. Description of the Related Art A conventional amplifier circuit is configured as shown in FIG. The amplifier circuit shown in FIG. 2 supplies the output voltage of the voltage amplifying stage 111 to a power amplifying stage 112 composed of complementary transistors 121 and 122 to amplify the power and drive a load such as a speaker. The output voltage from the power amplification stage 111 and the output voltage from the power amplification stage 112 are selected by a switch 113 so that one of them is selected and negatively fed back to the voltage amplification stage 111. In such a conventional amplifying circuit, when the output voltage of the power amplifying stage 112 is negatively fed back by the changeover switch 113, the voltage amplifying stage 111 and the power amplifying device are connected at a high frequency. Since feedback is not applied due to the difference in the frequency characteristics of the amplification stage 112, there is a problem that sound quality is deteriorated when the audio amplifier is used. Further, when the output voltage of the voltage amplifying stage 111 is selected and negatively fed back by the changeover switch 113, there is a problem that the distortion of the output signal of the amplifier circuit remains and the distortion cannot be removed. An object of the present invention is to provide an amplifier circuit in which an increase in distortion is suppressed. [0005] [0006] [0007] amplification circuit SUMMARY OF THE INVENTION The present invention is an amplifier circuit that includes a power amplifier stage which is driven by the output voltage of the voltage amplifier stage and said voltage amplification stage in a selecting means for selecting either one of or is negatively fed back to the AC component of the output voltage if the power amplifier stage is negatively fed back to the AC component of the output voltage of the voltage amplifier stage to the voltage amplification stage to the voltage amplification stage, selected When the means selects negative feedback of the AC component of the output voltage of the voltage amplifying stage to the voltage amplifying stage, the power amplifying stage is operated in class A, and the selecting means controls the AC of the output voltage of the power amplifying stage.
Switching means for operating the power amplification stage in class AB or class B when the component is selected to be negatively fed back to the voltage amplification stage. According to amplification circuit of the present invention, when you choose to negative feedback AC component of the output voltage of the voltage amplifier stage to the voltage amplification stage by the selecting means, the output voltage of the voltage amplifier stage
Since the AC component is negatively fed back to the voltage amplification stage and the power amplification stage is operated in class A, the audio quality is not degraded because no feedback is applied when the audio amplifier is used.
Since the sound quality is improved and the power amplifying stage operates in class A, the distortion of the output signal of the amplifier circuit is reduced. When the selecting means selects the negative feedback of the AC component of the output voltage of the power amplification stage to the voltage amplification stage, the AC component of the output voltage of the power amplification stage is negatively fed back to the voltage amplification stage. the power amplification stage when is allowed to class AB or class B operation, power efficiency is improved. An embodiment of an amplifier circuit according to the present invention will be described. FIG. 1 is a block diagram showing a configuration of an amplifier circuit according to one embodiment of the present invention. An amplifier circuit according to an embodiment of the present invention is configured such that the output voltage of the voltage amplification stage 1 is selectively fed back to the voltage amplification stage 1 through the changeover switch 13 and selectively via the resistor 14. The output voltage of the amplification stage 1 is supplied to the power amplification stage 2 to drive the power amplification stage 2. The power amplification stage 2 includes Darlington-connected transistors 16 and 18, Darlington-connected transistors 17 and 19, a single-ended push-pull amplifier 3, diodes 21 and 22, resistors 23 and 24, and a resistor 2.
3, a bias circuit 4 comprising a switch 25 connected in parallel with the resistor 3 and a semi-fixed resistor 26 for adjustment connected in parallel with the resistor 24. The DC component of the output voltage of the power amplification stage 2 is converted into a resistor 27 and a capacitor 29. And a negative feedback to the voltage amplifying stage 1 via the resistor 28 and the AC component of the output voltage of the power amplifying stage 2 is negatively fed back to the voltage amplifying stage 1 via the resistor 14 through the switch 13. . Here, the changeover switch 13 and the switch 25 are interlocked and switched by a changeover signal.
When the output of the voltage amplification stage 1 is switched by the changeover switch 13 so as to provide negative feedback, the switch 25 is switched to the open state, the bias current of the power amplification stage 2 is set to the current value of the class A operation, and the idle current is reduced. When the output voltage of the power amplification stage 2 is switched to negative feedback by the changeover switch 13, the switch 25 is switched to the closed state and the bias current of the power amplification stage 2 is changed to AB.
The idle current is reduced by setting the current value of the class operation. In the amplifying circuit according to one embodiment of the present invention, the input signal is voltage-amplified by the voltage amplifying stage 1, and the output signal of the voltage amplifying stage 1 is power-amplified by the power amplifying stage 2. Is done. When the common contact of the changeover switch 13 is switched to the contact a side based on the changeover signal, the switch 2
5 is switched to the open state. Therefore, the switch 25
Is open, the bias current of the power amplification stage 2 is A
And the idle current of the power amplification stage 2 is increased. On the other hand, the output voltage of the voltage amplification stage 1 is negatively fed back to the voltage amplification stage 1 through the capacitor 15 via the resistor 14. In this case, since the AC component of the output voltage of the power amplification stage 2 is not negatively fed back to the voltage amplification stage 1, no feedback deviation occurs, and the idle current of the power amplification stage 2 is increased. The distortion of the output signal of the power amplification stage 2 is small. On the other hand, the output voltage of the power amplification stage 2 is negatively fed back in a DC manner via the resistor 27, the capacitor 29 and the resistor 28, so that the fluctuation of the DC voltage of the output voltage of the power amplification stage 2 is suppressed. When the common contact of the changeover switch 13 is switched to the contact b side based on the changeover signal, the switch 2
5 is switched to the closed state. Therefore, the switch 25
Is closed, the bias current of the power amplification stage 2 is A
The bias current value is set to the class B operation, and the idle current of the power amplification stage 2 is reduced. On the other hand, the DC component of the output voltage of power amplification stage 2 is negatively fed back to voltage amplification stage 1 via resistor 27, capacitor 29 and resistor 28, and the AC component of the output voltage of power amplification stage 2 is connected via resistor 14. The voltage is negatively fed back to the voltage amplification stage 1 through the capacitor 15. In this case, since the AC component of the output voltage of the power amplification stage 2 is negatively fed back to the voltage amplification stage 1, there is a possibility that a state in which no feedback is applied may occur. Due to the reduction, the power efficiency of the power amplification stage 2 will be improved. Therefore, in the case of an audio amplifier, the selector switch 13 selects the negative feedback of the output voltage of the voltage amplification stage 1 to the voltage amplification stage 1 when sound quality is emphasized, and the changeover switch when importance is placed on power efficiency. 13, the output voltage of the power amplification stage 2 is
In the amplifying circuit according to the embodiment of the present invention, the changeover switch 13 and the switch 25 are provided so that the voltage can be changed. Selects whether the output voltage of the amplification stage is negatively fed back to the voltage amplification stage and the voltage amplification stage is operated in class A, or the output voltage of the power amplification stage is negatively fed back to the voltage amplification stage and the power amplification stage is operated in class AB. Although the case where the power amplifier stage is configured to perform a negative feedback of the output voltage of the voltage amplifier stage to the voltage amplifier stage and operate the power amplifier stage in class A is omitted, and a switch for selection is omitted. Is also good. Further, when the output voltage of the power amplification stage is negatively fed back to the voltage amplification stage, the power amplification stage may be operated in class B. [0021] According As described above, according to the present invention the amplification circuit of the present invention, when you choose to negative feedback AC component of the output voltage of the voltage amplifier stage to the voltage amplifier stage, Output of voltage amplification stage
The AC component of the voltage is negatively fed back to the voltage amplification stage, and the power amplification stage
Because but is operated Class A, the feedback off does not occur, and distortion of an output signal of the amplifier circuit is reduced, when you choose to negative feedback AC component of the output voltage of the power amplification stage to the voltage amplification stage Although feedback feedback may occur, the power amplification stage operates in class AB or class B, so that the effect of improving the power efficiency and the effect of increasing the range of selection can be obtained.
【図面の簡単な説明】
【図１】本発明の実施の一形態にかかる増幅回路の構成
を示すブロック図である。
【図２】従来の増幅回路の構成を示すブロック図であ
る。
【符号の説明】
１ 電圧増幅段
２ 電力増幅段
３ シングルエンデッドプッシュプル増幅器
４ バイアス回路
１３ 切り換えスイッチ
２５ スイッチBRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of an amplifier circuit according to one embodiment of the present invention. FIG. 2 is a block diagram illustrating a configuration of a conventional amplifier circuit. [Description of Signs] 1 voltage amplification stage 2 power amplification stage 3 single-ended push-pull amplifier 4 bias circuit 13 switch 25 switch
───────────────────────────────────────────────────── フロントページの続き (72)発明者 斎藤 誠 東京都渋谷区道玄坂１丁目14番６号 株 式会社ケンウッド内 (72)発明者 百瀬 敏倫 東京都渋谷区道玄坂１丁目14番６号 株 式会社ケンウッド内 (56)参考文献 特開 昭58−124308（ＪＰ，Ａ) (58)調査した分野(Int.Cl.7，ＤＢ名) H03F 1/00 - 3/72 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Makoto Saito 1-14-6 Dogenzaka, Shibuya-ku, Tokyo Stock Company Kenwood (72) Inventor Toshinori Momose 1-16-16 Dogenzaka, Shibuya-ku, Tokyo Stock Company (56) References JP-A-58-124308 (JP, A) (58) Fields investigated (Int. Cl. 7 , DB name) H03F 1/00-3/72
Claims (1)
って駆動される電力増幅段とを備えた増幅回路におい
て、 電圧増幅段の出力電圧の交流成分を電圧増幅段へ負帰還
させるか電力増幅段の出力電圧の交流成分を電圧増幅段
へ負帰還させるかの何れか一方を選択する選択手段と、 選択手段によって電圧増幅段の出力電圧の交流成分を電
圧増幅段へ負帰還することを選択したとき電力増幅段を
Ａ級動作させ、かつ選択手段によって電力増幅段の出力
電圧の交流成分を電圧増幅段へ負帰還することを選択し
たとき電力増幅段をＡＢ級またはＢ級動作させる切り換
え手段とを備えたことを特徴とする増幅回路。(57) [Claim 1] In an amplifier circuit including a voltage amplifying stage and a power amplifying stage driven by an output voltage of the voltage amplifying stage, an AC component of an output voltage of the voltage amplifying stage is reduced . Selecting means for selecting either negative feedback to the voltage amplification stage or negative feedback of the AC component of the output voltage of the power amplification stage to the voltage amplification stage, and selecting the AC component of the output voltage of the voltage amplification stage by the selection means. The power amplification stage is operated in class A when negative feedback to the voltage amplification stage is selected, and the power amplification stage is selected when negative feedback of the AC component of the output voltage of the power amplification stage is selected by the selection means. And a switching means for performing class AB or class B operation.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18596497A JP3460040B2 (en) | 1997-06-27 | 1997-06-27 | Amplifier circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP18596497A JP3460040B2 (en) | 1997-06-27 | 1997-06-27 | Amplifier circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH1127054A JPH1127054A (en) | 1999-01-29 |
| JP3460040B2 true JP3460040B2 (en) | 2003-10-27 |
Family
ID=16179965
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP18596497A Expired - Fee Related JP3460040B2 (en) | 1997-06-27 | 1997-06-27 | Amplifier circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3460040B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB2410142A (en) * | 2004-01-13 | 2005-07-20 | Gordon Leslie Scott | An audio power amplifier with automatic class selection |
-
1997
- 1997-06-27 JP JP18596497A patent/JP3460040B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH1127054A (en) | 1999-01-29 |
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