JPS62216410A - Variable gain amplifier - Google Patents

Variable gain amplifier

Info

Publication number
JPS62216410A
JPS62216410A JP5710386A JP5710386A JPS62216410A JP S62216410 A JPS62216410 A JP S62216410A JP 5710386 A JP5710386 A JP 5710386A JP 5710386 A JP5710386 A JP 5710386A JP S62216410 A JPS62216410 A JP S62216410A
Authority
JP
Japan
Prior art keywords
feedback circuit
photocoupler
amplifier
negative feedback
gain
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
Application number
JP5710386A
Other languages
Japanese (ja)
Inventor
Toshiro Sakane
坂根　敏朗
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fujitsu Ltd
Original Assignee
Fujitsu Ltd
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Fujitsu Ltd filed Critical Fujitsu Ltd
Priority to JP5710386A priority Critical patent/JPS62216410A/en
Publication of JPS62216410A publication Critical patent/JPS62216410A/en
Pending legal-status Critical Current

Links

Abstract

PURPOSE:To apply a variable gain amplifier to even a signal including a DC component or a very low frequency component by constituting a negative feedback circuit where a DC cutting capacitor is not used for feedback from the output side to the input side of the amplifier. CONSTITUTION:A photocoupler 2 is connected to a feedback circuit of an amplifier 1 to constitute the negative feedback circuit, and a gain control signal is supplied to a light emitting element 4 of the photocoupler 2, and the resistance between terminals of a photosensitive element 3 of the photocoupler 2 is changed to control the feedback quantity of the negative feedback circuit. Since the photocoupler 2 has control terminals A and B independent of the photosensitive element 3 operated as a variable resistance element, the DC cutting capacitor is unnecessary in the feedback circuit. Thus, the feedback quantity of the negative feedback circuit is controlled stably up to a DC area, and consequently, a good frequency characteristic is obtained.

Description

【発明の詳細な説明】 〔）既　　要〕 増幅器回路と独立した利得制御信号入力端子を有するフ
ォトカプラーの感光素子を増幅器の負帰還回路に挿入し
、外部からこのフォトカプラーの発光素子に利得制御信
号を供給して、このフォトカプラーの感光素子の端子間
の抵抗を変化させることにより、増幅器の利得を直流成
分を含む信号についても制御できるようにしたものであ
る。[Detailed description of the invention] [) Already required] A photosensitive element of a photocoupler having a gain control signal input terminal independent of the amplifier circuit is inserted into the negative feedback circuit of the amplifier, and gain control is applied to the light emitting element of this photocoupler from the outside. By supplying a signal and changing the resistance between the terminals of the photosensitive element of this photocoupler, the gain of the amplifier can be controlled even for signals containing DC components.

〔産業上の利用分野〕[Industrial application field]

本発明は、ベースバンドのビデオ信号などの直流成分な
いしは極めて低周波の成分を含む信号の増幅器の利得制
御に関する。The present invention relates to gain control of an amplifier for a signal including a DC component or an extremely low frequency component, such as a baseband video signal.

〔従来の技術〕[Conventional technology]

従来、この種の増幅器として、ＰＩＮダイオードを利用
した可変減衰器を増幅器帰還回路内に接続し、このＰＩ
Ｎダイオードの電流による抵抗値変化を利用して、増幅
器の利得を制御するものが知られていた。Conventionally, in this type of amplifier, a variable attenuator using a PIN diode is connected in the amplifier feedback circuit, and this PI
It has been known to control the gain of an amplifier by utilizing the change in resistance value caused by the current of an N diode.

〔発明が解決しようとする問題点〕[Problem that the invention seeks to solve]

上記の利得制御のようにＰＩＮダイオードのような２端
子の制御デバイスを負帰還回路に用いると、この帰還回
路内に直流成分遮断用のコンデンサを必要とするので、
低域側の帰還量を大きくとることができず、したがって
直流成分を含む信号については実質上利得を制御するこ
とができなかった。When a two-terminal control device such as a PIN diode is used in the negative feedback circuit as in the gain control described above, a capacitor for cutting off the DC component is required in the feedback circuit.
It is not possible to increase the amount of feedback on the low frequency side, and therefore it is virtually impossible to control the gain of signals containing DC components.

本発明は、増幅器の出力側から入力側に帰還するために
直流分の遮断用コンデンサを使用しない負帰還回路を構
成することにより、低周波域での負帰還量の減少による
高利得現象を防止し、直流分ないしは極めて低周波の成
分を含む信号にも適用できる可変利得増幅器を提供する
ことを目的とする。The present invention prevents high gain phenomena due to a decrease in the amount of negative feedback in the low frequency range by configuring a negative feedback circuit that does not use a DC blocking capacitor to feed back from the output side to the input side of the amplifier. However, it is an object of the present invention to provide a variable gain amplifier that can be applied to signals containing DC components or extremely low frequency components.

〔問題点を解決するための手段〕[Means for solving problems]

第１図に示す原理図のように、増幅器（１）の帰還回路
に、フォトカプラー（２）を接続して負帰還回路を構成
し、利得制御信号を該フォトカプラー（２）の発光素子
（４）に供給して、このフォトカプラー（２）の感光素
子（３）の端子間の抵抗を変化させて負帰還回路の帰還
量をコントロールするようにしたものである。As shown in the principle diagram shown in FIG. 1, a negative feedback circuit is constructed by connecting a photocoupler (2) to the feedback circuit of an amplifier (1), and a gain control signal is sent to the light emitting element (2) of the photocoupler (2). 4) to change the resistance between the terminals of the photosensitive element (3) of this photocoupler (2) to control the feedback amount of the negative feedback circuit.

〔作　用〕[For production]

フォトカプラー（２）が可変抵抗素子として動作する感
光素子（３）とは独立した制御端子（Ａ、Ｂ）を有する
ので、負帰還回路中に直流遮断用コンデンサを必要とせ
ず、直流領域まで安定に負帰還回路の帰還量を制御でき
、従って良好な周波数特性を得ることができる。Since the photocoupler (2) has control terminals (A, B) independent of the photosensitive element (3) that operates as a variable resistance element, there is no need for a DC cutoff capacitor in the negative feedback circuit, and it is stable up to the DC region. The feedback amount of the negative feedback circuit can be controlled, and therefore good frequency characteristics can be obtained.

〔実施例〕〔Example〕

第２図は、本発明の１実施例を示す回路図で、第１図の
原理図に示した増幅器（１）は（１１。FIG. 2 is a circuit diagram showing one embodiment of the present invention, and the amplifier (1) shown in the principle diagram of FIG. 1 is (11).

１２）に、フォトカプラー（２）は（２１，２２）に、
感光素子（３）は（３１，３２）に、発光素子（４）は
（４＋、４□）にそれぞれ対応する。12), the photocoupler (2) is (21, 22),
The photosensitive element (3) corresponds to (31, 32), and the light emitting element (4) corresponds to (4+, 4□), respectively.

トランジスタ（１１，１２）から構成される増幅器（１
）の出力側゛トランジスタ（１□）のエミッタ出力端子
と入力側トランジスタ（１１）のベース入力端子とを、
互いに双方向にできるように２つのフォトカプラー（２
１，２２）を感光素子（３１，３２）の導電方向が反対
になるように組合せて上記増幅器（１）の出力側と入力
側とを結合して負帰還回路としたものであり、各フォト
カプラー（２１，２２）の発光素子（４１，４２）の端
子Ｃ，Ｄを並列に接続した信号入力端子Ａ。An amplifier (1) consisting of transistors (11, 12)
) on the output side ``the emitter output terminal of the transistor (1□) and the base input terminal of the input side transistor (11),
Two photocouplers (2
1, 22) are combined so that the conductive directions of the photosensitive elements (31, 32) are opposite, and the output side and input side of the amplifier (1) are connected to form a negative feedback circuit. Signal input terminal A in which terminals C and D of light emitting elements (41, 42) of couplers (21, 22) are connected in parallel.

Ｂに利得制御信号を印加するようにして可変利得増幅器
を構成したものである。A variable gain amplifier is constructed by applying a gain control signal to B.

第３図は、本発明の他の実施例を示す回路図で、第２図
と同様な対応関係で示す。第２図のトランジスタ結合回
路により構成した増幅器（１）を１つの演算増幅器（１
３）に置き換えるとともに、導電方向に互いに逆方向に
なるような感光素子（３３，３−）で発光素子（４３）
を共通の光信号源とするように構成した１個のフォトカ
プラー（２３）で可変利得増幅器を構成したものである
。FIG. 3 is a circuit diagram showing another embodiment of the present invention, and is shown in the same correspondence as FIG. 2. The amplifier (1) constituted by the transistor combination circuit shown in Fig. 2 is combined into one operational amplifier (1).
3) and a light-emitting element (43) with photosensitive elements (33, 3-) whose conductive directions are opposite to each other.
A variable gain amplifier is constructed by one photocoupler (23) configured to use a common optical signal source.

なお、上記実施例ではフォトカプラー（２）として双方
向性のもので説明したが、単一方法のものであってもよ
い。In the above embodiment, the photocoupler (2) is described as a bidirectional photocoupler, but it may be of a single type.

〔発明の効果〕〔Effect of the invention〕

本発明は、以上説明したような構成を有するので、増幅
器と分離して利得制御信号を与えることができるので、
負帰還回路が直流分を帰還することができるようになり
、直流域を含む信号の利得を安定に制御できるという格
別の効果を奏する。Since the present invention has the configuration as described above, it is possible to provide a gain control signal separately from the amplifier.
The negative feedback circuit is now able to feed back the direct current component, and the special effect is that the gain of the signal including the direct current region can be stably controlled.

【図面の簡単な説明】[Brief explanation of drawings]

第１図は本発明の原理図、第２図は、本発明の１実施例
を示す回路図、第３図は、本発明の他の実施例を示す回
路図である。 ２．２１〜２３・・・フォトカプラー、３，３１〜３４
・・・フォトカプラーの感光素子、４，４１〜４３・・
・フットカプラーの発光素子。FIG. 1 is a principle diagram of the present invention, FIG. 2 is a circuit diagram showing one embodiment of the invention, and FIG. 3 is a circuit diagram showing another embodiment of the invention. 2.21-23...Photocoupler, 3,31-34
...Photocoupler photosensitive element, 4,41-43...
- Foot coupler light emitting element.

Claims (1)

【特許請求の範囲】[Claims] 増幅器（１）の帰還回路に、発光素子（４）と感光素子
（３）とからなるフォトカプラー（２）の該感光素子（
３）を接続して負帰還回路を構成し、利得制御信号を該
フォトカプラー（２）の該発光素子（４）に供給して前
記感光素子（３）の抵抗値を制御することにより、増幅
器（１）の利得を制御するようにしたことを特徴とする
可変利得増幅器。A photosensitive element (2) of a photocoupler (2) consisting of a light emitting element (4) and a photosensitive element (3) is connected to the feedback circuit of the amplifier (1).
3) to form a negative feedback circuit, and supply a gain control signal to the light emitting element (4) of the photocoupler (2) to control the resistance value of the photosensitive element (3). A variable gain amplifier characterized in that (1) the gain is controlled.
JP5710386A 1986-03-17 1986-03-17 Variable gain amplifier Pending JPS62216410A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
JP5710386A JPS62216410A (en) 1986-03-17 1986-03-17 Variable gain amplifier

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
JP5710386A JPS62216410A (en) 1986-03-17 1986-03-17 Variable gain amplifier

Publications (1)

Publication Number Publication Date
JPS62216410A true JPS62216410A (en) 1987-09-24

Family

ID=13046173

Family Applications (1)

Application Number Title Priority Date Filing Date
JP5710386A Pending JPS62216410A (en) 1986-03-17 1986-03-17 Variable gain amplifier

Country Status (1)

Country Link
JP (1) JPS62216410A (en)

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