JPH05299956A - Automatic level control circuit - Google Patents
Automatic level control circuitInfo
- Publication number
- JPH05299956A JPH05299956A JP4126679A JP12667992A JPH05299956A JP H05299956 A JPH05299956 A JP H05299956A JP 4126679 A JP4126679 A JP 4126679A JP 12667992 A JP12667992 A JP 12667992A JP H05299956 A JPH05299956 A JP H05299956A
- Authority
- JP
- Japan
- Prior art keywords
- amplifier
- output
- level control
- control circuit
- automatic level
- 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
Links
Landscapes
- Control Of Amplification And Gain Control (AREA)
- Amplifiers (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は出力レベルを一定にする
自動レベル制御回路に関し、特にシステムエラーのない
自動レベル制御回路に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic level control circuit for keeping an output level constant, and more particularly to an automatic level control circuit having no system error.
【０００２】[0002]
【従来の技術】従来、オペアンプを用いて検波された高
周波信号と基準電圧を差動増幅してレベルを一定に保つ
自動レベル制御回路として図２に示すものがある。この
回路では、可変減衰器付増幅器１の出力を信号検波器２
で検出し、この検出出力をＤＣ増幅器３で増幅した上で
差動増幅器４において基準電圧と比較し、得られた差電
圧により前記可変減衰器付増幅器１の減衰量を制御し、
出力レベルを一定に保持している。差動増幅器４の出力
側には電流制限用抵抗５が接続される。2. Description of the Related Art Conventionally, there is an automatic level control circuit shown in FIG. 2 as an automatic level control circuit for maintaining a constant level by differentially amplifying a high frequency signal detected by an operational amplifier and a reference voltage. In this circuit, the output of the amplifier 1 with a variable attenuator is connected to the signal detector 2
And the detected output is amplified by the DC amplifier 3 and then compared with the reference voltage in the differential amplifier 4, and the attenuation amount of the amplifier with variable attenuator 1 is controlled by the obtained difference voltage.
The output level is kept constant. A current limiting resistor 5 is connected to the output side of the differential amplifier 4.
【０００３】[0003]
【発明が解決しようとする課題】このような従来の自動
レベル制御回路においては、一般にループ時定数を大き
くとる必要があるため、差動増幅器５の時定数を大きく
設定している。このため、電源ＯＮ，ＯＦＦの切換え時
に差動増幅器５の出力が瞬間的に電源電圧付近まで上昇
し、出力のオーバシュートが発生し、システムエラーを
引起こすという問題がある。本発明の目的は、このよう
な電源ＯＮ，ＯＦＦ時の出力のオーバシュートを防止し
た自動レベル制御回路を提供することにある。In such a conventional automatic level control circuit, since it is generally necessary to set a large loop time constant, the time constant of the differential amplifier 5 is set large. Therefore, there is a problem that the output of the differential amplifier 5 momentarily rises to near the power supply voltage when the power is turned on and off, an output overshoot occurs, and a system error occurs. It is an object of the present invention to provide an automatic level control circuit which prevents such output overshoot when the power is turned on and off.
【０００４】[0004]
【課題を解決するための手段】本発明は、可変減衰器付
増幅器の出力と基準電圧と比較して減衰量を制御する差
動増幅器の出力側にプルアップ回路を設ける。このプル
アップ回路は、可変減衰器付増幅器の減衰量が大きい方
向へプルアップするように構成する。According to the present invention, a pull-up circuit is provided on the output side of a differential amplifier which controls the amount of attenuation by comparing the output of an amplifier with a variable attenuator with a reference voltage. This pull-up circuit is configured to pull up in the direction in which the amount of attenuation of the amplifier with variable attenuator is large.
【０００５】[0005]
【作用】差動増幅器の時定数が大きい場合でも、電源Ｏ
Ｎ，ＯＦＦ時にはプルアップ回路により可変減衰器増幅
器の減衰量を制御し、出力のオーバシュートを防止す
る。Operation: Even if the time constant of the differential amplifier is large, the power supply O
At N and OFF, the pull-up circuit controls the amount of attenuation of the variable attenuator amplifier to prevent output overshoot.
【０００６】[0006]
【実施例】次に、本発明について図面を参照して説明す
る。図１は本発明の一実施例である。本実施例におい
て、１は可変減衰器付増幅器、２はこの可変減衰器付増
幅器１の出力を検出して検波する信号検波器、３はＤＣ
増幅器、４はＤＣ増幅器３の出力と基準電圧とを比較し
て差電圧を出力する差動増幅器である。そして、この差
動増幅器４の出力側に電流制限用抵抗５を接続し、更に
電流制限用抵抗６とツェナダイオード７からなるプルア
ップ回路を有している。このプルアップ回路は、可変減
衰器付増幅器１の減衰量が大きくなる方向の電圧（ここ
では、負電圧）にプルアップされるように構成されてい
る。DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention. In this embodiment, 1 is an amplifier with a variable attenuator, 2 is a signal detector for detecting and detecting the output of the amplifier with a variable attenuator 1, and 3 is a DC.
Amplifiers 4 are differential amplifiers that compare the output of the DC amplifier 3 with a reference voltage and output a difference voltage. A current limiting resistor 5 is connected to the output side of the differential amplifier 4, and a pull-up circuit including a current limiting resistor 6 and a Zener diode 7 is provided. The pull-up circuit is configured to be pulled up to a voltage (here, a negative voltage) in a direction in which the amount of attenuation of the amplifier with variable attenuator 1 increases.
【０００７】このように構成すれば、可変減衰器付増幅
器１の出力を信号検波器２で検出し、これを差動増幅器
４で基準電圧と比較して得られた差電圧によって前記可
変減衰器付増幅器１の減衰量を制御して自動レベル制御
を行うことはこれまでと同じである。そして、この作用
に加えて、ここでは差動増幅器４の出力側に電流制限用
抵抗６とツェナーダイオード７からなるプルアップ回路
を設けていることにより、電源の立上げ時には可変減衰
器付増幅器１の減衰量は最大値から通常値へ変化され、
電源の立下げ時には通常値から最大値へと変化されるた
め、可変減衰器付増幅器１の制御電圧が増大することが
なく、出力のオーバシュートは発生しなくなる。According to this structure, the output of the amplifier with variable attenuator 1 is detected by the signal detector 2 and the differential amplifier 4 compares the output with the reference voltage to obtain the variable attenuator. Controlling the amount of attenuation of the attached amplifier 1 to perform automatic level control is the same as before. In addition to this function, a pull-up circuit including a current limiting resistor 6 and a Zener diode 7 is provided on the output side of the differential amplifier 4 here, so that the amplifier 1 with a variable attenuator is activated when the power supply is turned on. The attenuation of is changed from the maximum value to the normal value,
Since the normal value is changed to the maximum value when the power supply is turned off, the control voltage of the amplifier with variable attenuator 1 does not increase, and output overshoot does not occur.
【０００８】[0008]
【発明の効果】以上説明したように本発明の自動レベル
制御回路は、時定数の大きい差動増幅器出力を減衰量の
大きい方向へプルアップしておくことにより、電源Ｏ
Ｎ，ＯＦＦ時のレベルオーバシュートを防止でき、シテ
スムエラーを未然に防止できる。As described above, the automatic level control circuit of the present invention pulls up the output of the differential amplifier having a large time constant in the direction in which the amount of attenuation is large so that the power source O
It is possible to prevent the level overshoot at the time of N and OFF, and prevent the system error.
【図１】本発明の自動レベル制御回路の一実施例の回路
図である。FIG. 1 is a circuit diagram of an embodiment of an automatic level control circuit of the present invention.
【図２】従来の自動レベル制御回路の一例の回路図であ
る。FIG. 2 is a circuit diagram of an example of a conventional automatic level control circuit.
１ 可変減衰器付増幅器 ２ 信号検波器 ３ ＤＣ増幅器 ４ 差動増幅器 ５，６ 電流制限用抵抗 ７ ツェナーダイオード 1 Amplifier with variable attenuator 2 Signal detector 3 DC amplifier 4 Differential amplifier 5,6 Current limiting resistor 7 Zener diode
Claims (2)
力を検出する信号検波器と、検出された電圧を基準電圧
と比較して差電圧を出力する差動増幅器とを備え、この
差動増幅器から出力される差電圧に基づいて前記可変減
衰器付増幅器の減衰量を制御する自動レベル制御回路に
おいて、前記差動増幅器の出力側にプルアップ回路を設
けたことを特徴とする自動レベル制御回路。1. A differential attenuator-equipped amplifier, a signal detector for detecting an output of the amplifier, and a differential amplifier for comparing a detected voltage with a reference voltage to output a differential voltage. In an automatic level control circuit for controlling the amount of attenuation of the amplifier with a variable attenuator based on a differential voltage output from the amplifier, a pull-up circuit is provided on the output side of the differential amplifier. circuit.
の減衰量が大きい方向へプルアップしてなる請求項１の
自動レベル制御回路。2. The automatic level control circuit according to claim 1, wherein the pull-up circuit is pulled up in a direction in which the amount of attenuation of the amplifier with a variable attenuator is large.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4126679A JPH05299956A (en) | 1992-04-21 | 1992-04-21 | Automatic level control circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4126679A JPH05299956A (en) | 1992-04-21 | 1992-04-21 | Automatic level control circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH05299956A true JPH05299956A (en) | 1993-11-12 |
Family
ID=14941177
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP4126679A Pending JPH05299956A (en) | 1992-04-21 | 1992-04-21 | Automatic level control circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH05299956A (en) |
-
1992
- 1992-04-21 JP JP4126679A patent/JPH05299956A/en active Pending
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