JPH0450646Y2

JPH0450646Y2 -

Info

Publication number: JPH0450646Y2
Application number: JP1986045691U
Authority: JP
Priority date: 1986-03-28
Filing date: 1986-03-28
Publication date: 1992-11-30
Also published as: JPS62158922U

Description

【考案の詳細な説明】〔概要〕コントロール信号により出力電圧値を固定する
ことが可能な電子ボリウム装置。[Detailed description of the invention] [Summary] An electronic volume device that can fix the output voltage value using a control signal.

[Industrial application field]

本考案は、デジタル値で出力アナログ電圧を変
更できる電子ボリウム装置に関する。 The present invention relates to an electronic volume device that can change an output analog voltage using a digital value.

この電子ボリウムは、各種オーデイオ機器、
PCM端局装置などで使用できる。 This electronic volume is suitable for various audio equipment,
Can be used with PCM terminal equipment, etc.

[Conventional technology]

タツプ付き抵抗、そのタツプ選択用のスイツ
チ、および増幅器を用い、デジタル信号でスイツ
チをオンオフして増幅器入力信号を変えると出力
信号が変り、デジタル制御型の電子ボリウムが得
られる。しかし従来のこの種装置では、多ビツト
デジタル信号に対してはタツプ数又は抵抗器数が
多数になり、又はスイツチのオン抵抗が影響して
精度が出ないという問題がある。本考案者はこの
ような点を改善した電子ボリウムを先に開発した
が、その概要を第２図に示す。 Using a resistor with a tap, a switch for selecting the tap, and an amplifier, when the switch is turned on and off using a digital signal and the amplifier input signal is changed, the output signal changes, and a digitally controlled electronic volume is obtained. However, in conventional devices of this kind, there is a problem in that accuracy is poor due to the large number of taps or resistors for multi-bit digital signals, or the influence of the on-resistance of the switch. The inventor of the present invention previously developed an electronic volume that improved on these points, an outline of which is shown in FIG.

第２図でＡは演算増幅器、R₁はアナログ入力
信号（音声信号）を受ける可変抵抗、R₂は増幅
器Ａの出力電圧を受ける可変抵抗である。可変抵
抗R₁，R₂の出力電圧が増幅器Ａの＋，−入力端子
に加えられる。入力電圧をVi、増幅器出力電圧
Vo、抵抗R₁，R₂の分圧比をK₁，K₂とすると、
増幅器Ａの利得は充分に高いので次式が成立す
る。 In FIG. 2, A is an operational amplifier, R ₁ is a variable resistor that receives an analog input signal (audio signal), and R ₂ is a variable resistor that receives the output voltage of amplifier A. The output voltages of variable resistors R ₁ and R ₂ are applied to the + and - input terminals of amplifier A. Input voltage is Vi, amplifier output voltage
If Vo and the voltage division ratio of resistors R ₁ and R ₂ are K ₁ and K ₂ ,
Since the gain of amplifier A is sufficiently high, the following equation holds true.

Vi・K₁＝Vo・K₂ Vo＝K₁／K₂・Vi (1) K₁，K₂は１以下の正数で共に可変であるから
この回路の利得は１より大、１より小の範囲で任
意に変えることができる。 Vi・K ₁ = Vo・K ₂ Vo=K ₁ /K ₂・Vi (1) Since K ₁ and K ₂ are positive numbers less than or equal to 1 and both are variable, the gain of this circuit is greater than 1 and less than 1. It can be changed arbitrarily within the range.

可変抵抗R₁，R₂は複数のタツプを持つポテン
シヨンメータで、該タツプをトリー型スイツチ回
路で選択し、該回路の各スイツチをデジタル値の
各ビツトでオンオフする。演算増幅器Ａの入力抵
抗は非常に高いので、スイツチのオン抵抗が高く
てもそれによる電圧降下は無視してよく、従つて
この回路はスイツチのオン抵抗の影響を受けない
電子ボリウムを提供する。またK₁／K₂で利得を
変えるので、比較的少数のタツプ数（抵抗数）で
多段の制御を行なう（多ビツトデジタル入力に対
処する）ことができる。 The variable resistors R ₁ and R ₂ are potentiometers having a plurality of taps, which are selected by a tree-type switch circuit, and each switch of the circuit is turned on and off by each bit of a digital value. Since the input resistance of operational amplifier A is very high, the voltage drop due to the high on-resistance of the switch is negligible, and thus this circuit provides an electronic volume that is independent of the on-resistance of the switch. Also, since the gain is changed by K ₁ /K ₂ , multi-stage control can be performed with a relatively small number of taps (number of resistors) (to cope with multi-bit digital input).

[Problem that the invention attempts to solve]

このような電子ボリウムでは、入力信号を完全
に遮断して出力電圧を０にすることも必要であ
る。しかし一般にはかゝる電子ボリウムはdB単
位で扱われており、０〜−10dB，０〜−20dBな
どが可調整範囲とされる。出力０には−∞dBが
必要であるが、かゝるステツプは用意されていな
い。 In such an electronic volume, it is also necessary to completely cut off the input signal and set the output voltage to zero. However, such electronic volume is generally treated in dB units, and the adjustable range is 0 to -10 dB, 0 to -20 dB, etc. Output 0 requires -∞dB, but such a step is not provided.

この第２図の回路で出力０にするには、簡単に
は図示のように増幅器Ａの出力端にスイツチSW
を設ければよい。この切換スイツチは固定接点１
は増幅器Ａの出力端に、また固定接点０はグラン
ドに接続されているので、コントロール信号CS
によりスイツチを１側に倒せば増幅器出力電圧
Voが、そしてスイツチを０側に倒せば０電圧が
出力される。 To set the output to 0 in the circuit shown in Figure 2, simply connect the switch SW to the output terminal of amplifier A as shown in the diagram.
All you have to do is set it up. This changeover switch has fixed contact 1
is connected to the output terminal of amplifier A, and fixed contact 0 is connected to ground, so the control signal CS
If you turn the switch to the 1 side, the amplifier output voltage
If Vo is set and the switch is turned to the 0 side, 0 voltage will be output.

しかしこの回路ではやはりスイツチSWのオン
抵抗が問題になる。スイツチのオン抵抗が高い
と、後段回路より流入してくる電流が電圧降下を
作り、出力は０電圧でなくなる。 However, in this circuit, the on-resistance of the switch SW becomes a problem. If the on-resistance of the switch is high, the current flowing in from the subsequent circuit will cause a voltage drop, and the output will no longer be 0 voltage.

本考案は簡単な手段で確実に０電圧を出力する
ことができる電子ボリウムを提供しようとするも
のである。 The present invention aims to provide an electronic volume that can reliably output zero voltage using simple means.

[Effect]

本考案回路を第１図に示す。第２図と同じ部分
には同じ符号が付してあり、そして両者を比較す
れば明らかなように第１図はスイツチS₁，S₂を挿
入している点が第２図と異なる。切換スイツチS₁
はその固定接点１がポテンシヨメータR₁の出力
端に、固定接点０はグランドに接続され、切換ス
イツチS₂はその固定接点１がポテンシヨメータ
R₂の出力端に、固定接点０が増幅器Ａの出力端
に接続される。 The circuit of the present invention is shown in FIG. The same parts as in FIG. 2 are designated by the same reference numerals, and as is clear from a comparison of the two, FIG. 1 differs from FIG. 2 in that switches S ₁ and S ₂ are inserted. Changeover switch S ₁
The fixed contact 1 of the switch S2 is connected to the output end of the potentiometer _R1 , the fixed contact 0 is connected to the ground, and the fixed contact 1 of the changeover switch _S2 is connected to the output end of the potentiometer R1.
At the output of R ₂ a fixed contact 0 is connected to the output of amplifier A.

従つてスイツチS₂を接点０側に倒すと増幅器Ａ
は入力電圧に等しい出力電圧を生じる電圧ホロア
になり、そしてスイツチS₁を接点０側に倒すと増
幅器Ａの入力電圧は０になり、従つて該増幅器の
出力電圧は０になる。増幅器Ａの出力端にはスイ
ツチは入つていないからスイツチオン抵抗が入る
ことはなく、そして演算増幅器Ａの出力インピー
ダンスは低いから、後段回路からの電流流入があ
つても増幅器出力電圧が０より上昇することはな
い。スイツチS₁，S₂にはオン抵抗があるが、前述
のように演算増幅器Ａの入力インピーダンスは高
いので、該オン抵抗は問題になることはない。 Therefore, when switch S ₂ is turned to contact 0 side, amplifier A
becomes a voltage follower producing an output voltage equal to the input voltage, and when switch _S1 is turned to contact 0, the input voltage of amplifier A becomes zero, and therefore the output voltage of the amplifier becomes zero. Since there is no switch at the output terminal of amplifier A, there is no switch-on resistance, and the output impedance of operational amplifier A is low, so even if there is current inflow from the subsequent circuit, the amplifier output voltage will rise above 0. There's nothing to do. The switches S ₁ and S ₂ have on-resistances, but since the input impedance of operational amplifier A is high as described above, this on-resistance does not pose a problem.

〔Example〕

第３図に本考案の実施例を示す。抵抗R₁，R₂
は５個の同じ値の抵抗Ｒを直列接続したもので構
成され、各直列接続点にスイツチS₁₁〜S₁₄，S₃₁
〜S₃₄が接続され、これらのスイツチはスイツチ
S₂₁，S₂₂，S₄₁，S₄₂で選択され、増幅器Ａの＋，
−入力端子へ接続されるが、この間にスイツチ
S₁，S₂が挿入される。本回路では入力デジタル信
号は４ビツトとしており、その各ビツトA₁，A₂，
A₃，A₄がスイツチS₁₁〜S₄₁，S₂₁〜S₂₂，S₃₁〜
S₃₄，S₄₁〜S₄₂を切換える。図示のスイツチ位置
はA₁A₂A₃A₄＝0000に対応しており、可変抵抗R₁
の出力電圧はVi／５、可変抵抗R₂の出力電圧は
Vo／５である。つまりK₁＝K₂＝１／５であるか
ら本回路の利得は１で、Vi＝Voである。K₁，K₂
は１／５，２／５，３／５，４／５の範囲で変る
から利得Ｇ＝K₁／K₂はA₁〜A₄のデジタル値に応
じて１／４，１／３，１／２，２／３，３／４，
１，４／３，３／２，２，３，４のいずれかにな
る。 FIG. 3 shows an embodiment of the present invention. Resistance R ₁ , R ₂
is composed of five resistors R of the same value connected in series, and switches S ₁₁ to S ₁₄ , S ₃₁ are connected to each series connection point.
~S ₃₄ are connected and these switches are
S ₂₁ , S ₂₂ , S ₄₁ , S ₄₂ selects +,
– is connected to the input terminal, but the switch is not connected during this time.
S ₁ and S ₂ are inserted. In this circuit, the input digital signal is 4 bits, and each bit is A ₁ , A ₂ ,
A ₃ , A ₄ are switches S ₁₁ ~ S ₄₁ , S ₂₁ ~ S ₂₂ , S ₃₁ ~
Switch _S34 , _S41 to _S42 . The switch position shown corresponds to A ₁ A ₂ A ₃ A ₄ = 0000, and the variable resistor R ₁
The output voltage of is Vi/5, and the output voltage of variable resistor _R2 is
It is Vo/5. That is, since K ₁ =K ₂ =1/5, the gain of this circuit is 1, and Vi=Vo. _K1 , _K2
changes in the range of 1/5, 2/5, 3/5, and 4/5, so the gain G=K ₁ /K ₂ changes to 1/4, 1/3, and 1 depending on the digital values of A ₁ to A ₄ . /2,2/3,3/4,
It will be either 1, 4/3, 3/2, 2, 3, or 4.

スイツチS₁，S₂を０側に倒すと前述のように出
力電圧Voは０になり、この０電圧源のインピー
ダンスは増幅器Ａの出力インピーダンスで、非常
に低い。 When the switches S ₁ and S ₂ are turned to the 0 side, the output voltage Vo becomes 0 as described above, and the impedance of this 0 voltage source is the output impedance of the amplifier A, which is very low.

〔考案の効果〕以上説明したように本考案によれば電子ボリウ
ムにおいて、簡単な手段で特性のよい０電圧を出
力することができ、オーデイオ機器などに用いて
有効である。[Effects of the Invention] As explained above, according to the present invention, it is possible to output a zero voltage with good characteristics by a simple means in an electronic volume, and it is effective for use in audio equipment and the like.

[Brief explanation of drawings]

第１図は本考案の原理説明図、第２図は既提案
回路図、第３図は本考案の実施例を示す回路図で
ある。図面でR₁は第１の可変抵抗、R₂は第２の可変
抵抗、S₁は第１の切換スイツチ、S２は第２の切
換スイツチ、Ａは演算増幅器である。 FIG. 1 is a diagram illustrating the principle of the present invention, FIG. 2 is a previously proposed circuit diagram, and FIG. 3 is a circuit diagram showing an embodiment of the present invention. In the drawing, R ₁ is a first variable resistor, R ₂ is a second variable resistor, S ₁ is a first changeover switch, S2 is a second changeover switch, and A is an operational amplifier.

Claims

[Claims for Utility Model Registration] An operational amplifier having first and second input terminals and an output terminal, an input terminal and an output terminal, and generating a plurality of divided voltages from an analog voltage V1 input to the input terminal a first variable resistor R1 that selects one of the divided voltages according to the control of the first switching means using a digital signal and outputs it to the output terminal; a first selector switch S1 that selects one of the output terminal of the operational amplifier and the ground terminal connected to the ground voltage and connects the selected one to the first input terminal of the operational amplifier; A second switch inputs the voltage at the output end of the operational amplifier to generate a plurality of divided voltages, selects one of the divided voltages according to control of the second switch means using a digital signal, and outputs it to the output end. a second variable resistor R2 that selects one of the output terminal of the second variable resistor R2 and the output terminal of the operational amplifier according to the control signal and connects to the second input terminal of the operational amplifier. a changeover switch S2, in response to the control signal, the first changeover switch S1 selects the ground terminal and at the same time the second changeover switch S2 selects the output terminal of the operational amplifier. , the first changeover switch S1 selects the output end of the first variable resistor R1, and at the same time the second changeover switch S2 selects the output end of the second variable resistor R2. An electronic volume device characterized in that it takes either of the indicated states.