JP3166879B2 - Non-inverting amplifier - Google Patents
Non-inverting amplifierInfo
- Publication number
- JP3166879B2 JP3166879B2 JP24263592A JP24263592A JP3166879B2 JP 3166879 B2 JP3166879 B2 JP 3166879B2 JP 24263592 A JP24263592 A JP 24263592A JP 24263592 A JP24263592 A JP 24263592A JP 3166879 B2 JP3166879 B2 JP 3166879B2
- Authority
- JP
- Japan
- Prior art keywords
- resistor
- resistors
- capacitor
- input terminal
- inverting input
- 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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Description
【０００１】[0001]
【産業上の利用分野】本発明は、演算増幅器を用いた非
反転増幅器に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-inverting amplifier using an operational amplifier.
【０００２】[0002]
【従来の技術】従来、上記のような非反転増幅器には、
例えば図２に示すようなものがあった。同図において、
入力端子１０に供給された低周波信号は、コンデンサ１
２を介して演算増幅器１４の非反転入力端子に供給され
る。この非反転入力端子は、抵抗器１６を介して接地さ
れている。また、演算増幅器１４の出力側は、抵抗器１
８を介して反転入力端子に接続されている。この反転入
力端子は、抵抗器２０及びコンデンサ２２の直列回路を
介して接地されている。また、演算増幅器１４の出力側
はコンデンサ２４を介して出力端子２６に接続されてい
る。2. Description of the Related Art Conventionally, non-inverting amplifiers as described above include:
For example, there was one as shown in FIG. In the figure,
The low-frequency signal supplied to the input terminal 10 is
2 to the non-inverting input terminal of the operational amplifier 14. This non-inverting input terminal is grounded via a resistor 16. The output side of the operational amplifier 14 is connected to the resistor 1
8 is connected to the inverting input terminal. This inverting input terminal is grounded via a series circuit of a resistor 20 and a capacitor 22. The output side of the operational amplifier 14 is connected to an output terminal 26 via a capacitor 24.
【０００３】この非反転増幅器では、抵抗器１８の値を
Ｒｆ、抵抗器２０の抵抗値をＲｓとすると、その利得は
（Ｒｆ＋Ｒｓ）／Ｒｓで定まる。ここで、演算増幅器１
４に安価なものを使用すると、抵抗器１８には、抵抗値
Ｒｆが最大でも数ＭΩ程度のものしか使用することがで
きず、これに応じて抵抗器２０にも、抵抗値Ｒｓが１０
ＫΩのオーダーのものしか使用することができない。例
えば抵抗器１８には１ＭΩのものを、抵抗器２０には１
０ＫΩのものを使用する。In this non-inverting amplifier, if the value of the resistor 18 is Rf and the resistance of the resistor 20 is Rs, the gain is determined by (Rf + Rs) / Rs. Here, the operational amplifier 1
If an inexpensive resistor is used for the resistor 4, only a resistor 18 having a resistance value Rf of at most about several MΩ can be used.
Only those of the order of KΩ can be used. For example, a resistor 18 has a resistance of 1 MΩ and a resistor 20 has a resistance of 1 MΩ.
Use the one with 0 KΩ.
【０００４】抵抗器２０と直列に接続しているコンデン
サ２２は、演算増幅器１４に直流的な帰還が１００％か
かるようにするためのもので、もし、このコンデンサ２
２を設けなければ、演算増幅器１４の入力オフセット電
圧が１０１倍〔（Ｒｆ＋Ｒｓ）／Ｒｓ〕になって出力側
にオフセット電圧として現れて、演算増幅器１４のダイ
ナミックレンジを狭めてしまうからである。ここで、コ
ンデンサ２２の値は、例えば１μＦ程度のものが使用さ
れている。これは、抵抗器２０及びコンデンサ２２によ
って時定数回路が構成されており、この時定数が、この
非反転増幅器の低域遮断周波数に影響を与えるからであ
り、図２の場合、この遮断周波数が約１６Ｈｚ（１／２
π・１０ＫΩ・１μＦ）となるように、１μＦのものを
コンデンサ２２に使用している。[0004] A capacitor 22 connected in series with the resistor 20 is used to provide 100% DC feedback to the operational amplifier 14.
If 2 is not provided, the input offset voltage of the operational amplifier 14 becomes 101 times [(Rf + Rs) / Rs] and appears as an offset voltage on the output side, thereby narrowing the dynamic range of the operational amplifier 14. Here, the value of the capacitor 22 is, for example, about 1 μF. This is because a time constant circuit is formed by the resistor 20 and the capacitor 22, and the time constant affects the low cutoff frequency of the non-inverting amplifier. In the case of FIG. About 16Hz (1/2
1 μF) is used for the capacitor 22 so that π · 10 KΩ · 1 μF).
【０００５】[0005]
【発明が解決しようとする課題】しかし、１μＦもの大
きな容量のものを使用した場合、安価なものが存在せ
ず、チップ電解コンデンサやチップタンタルコンデンサ
等の高価なものを使用しなければならないという問題点
があった。また、このような大きな容量のものでは、そ
の精度が低く、この非反転増幅器を量産した場合に、低
域遮断周波数がばらつくという問題点もあった。However, when a capacitor having a capacitance as large as 1 μF is used, there is no inexpensive one, and expensive ones such as a chip electrolytic capacitor and a chip tantalum capacitor must be used. There was a point. In addition, such a large-capacity capacitor has a problem in that its accuracy is low, and when this non-inverting amplifier is mass-produced, the low-frequency cutoff frequency varies.
【０００６】この発明は、オフセット電圧を除去するた
めのコンデンサに小容量のものを使用できるようにし
て、コストダウンを図るともに、低域遮断周波数の精度
を向上させることを目的とする。SUMMARY OF THE INVENTION It is an object of the present invention to reduce the cost and improve the accuracy of the low cutoff frequency by making it possible to use a small-capacity capacitor for removing an offset voltage.
【０００７】[0007]
【課題を解決するための手段】上記の目的を達成するた
めに、本発明では、非反転入力端子に入力信号が供給さ
れる演算増幅器と、この演算増幅器の反転入力端子と出
力端子との間に直列に接続された複数の第１の抵抗器
と、反転入力端子と基準電位点との間、及び各第１の抵
抗器の接続点と基準電位点との間に、それぞれ接続され
た複数の第２の抵抗器とを、具備している。これら第２
の抵抗器は、各第１の抵抗器よりも値の小さいものであ
り、第１及び第２の抵抗器を１つずつ設けたときに所定
の利得を得るために必要な両抵抗値の比率よりも、前記
所定の利得を得るために設定された互いに対応する各第
１及び第２の抵抗器の抵抗値の比率が小さく、各第２の
抵抗器と直列にコンデンサを接続している。According to the present invention, there is provided an operational amplifier having an input signal supplied to a non-inverting input terminal, and an operational amplifier having an inverting input terminal and an output terminal connected to the operational amplifier. Connected between the inverting input terminal and the reference potential point, and between the connection point of each first resistor and the reference potential point. And a second resistor. These second
Are smaller in value than each of the first resistors, and the ratio of the two resistors required to obtain a predetermined gain when the first and second resistors are provided one by one. The ratio of the resistance value of each of the first and second resistors set to obtain the predetermined gain is smaller than that of the first and second resistors, and a capacitor is connected in series with each of the second resistors.
【０００８】[0008]
【作用】本発明によれば、複数の第１の抵抗器を直列に
演算増幅器の出力側と反転入力端子との間に接続してお
り、複数の第２の抵抗器を反転入力端子と基準電位点と
の間、及び各第１の抵抗器の接続点と基準電位点との間
に接続しているので、従来のものとほぼ同一の利得を得
ようとする場合、各第１の抵抗器の抵抗値と第２の抵抗
器の抵抗値との比率を、従来の反転入力端子と基準電位
点との間に接続されていた１つの抵抗器と、演算増幅器
の出力側と反転入力端子との間に接続されていた１つの
抵抗器との抵抗値の比率よりも小さくすることができ
る。よって、第２の抵抗器の抵抗値を従来の反転入力端
子と基準電位点との間に接続されていた１つの抵抗器よ
りも大きくすることができ、第２の抵抗器と直列に接続
されるコンデンサも、従来のものと同様な低域遮断周波
数とすれば、容量を従来のもののコンデンサよりも小さ
くすることができる。According to the present invention, a plurality of first resistors are connected in series between the output side of the operational amplifier and the inverting input terminal, and the plurality of second resistors are connected to the inverting input terminal and the reference. Since it is connected between the potential point and between the connection point of each first resistor and the reference potential point, when trying to obtain almost the same gain as the conventional one, each first resistor The ratio between the resistance value of the resistor and the resistance value of the second resistor is determined by using one resistor connected between the conventional inverting input terminal and the reference potential point, the output side of the operational amplifier, and the inverting input terminal. Can be made smaller than the ratio of the resistance value to one resistor connected between them. Therefore, the resistance value of the second resistor can be made larger than that of the conventional one resistor connected between the inverting input terminal and the reference potential point, and is connected in series with the second resistor. If the capacitor has a low cutoff frequency similar to that of the conventional capacitor, the capacitance can be made smaller than that of the conventional capacitor.
【０００９】[0009]
【実施例】この実施例の非反転増幅器では、入力端子３
０は、交流結合用のコンデンサ３２を介して演算増幅器
３４の非反転入力端子に接続されている。この非反転入
力端子は、抵抗器３６を介して接地されている。この抵
抗器３６は、入力端子３０に供給された低周波信号を非
反転入力端子に供給するためのものである。DESCRIPTION OF THE PREFERRED EMBODIMENTS In the non-inverting amplifier of this embodiment, the input terminal 3
0 is connected to a non-inverting input terminal of an operational amplifier 34 via a capacitor 32 for AC coupling. This non-inverting input terminal is grounded via a resistor 36. The resistor 36 is for supplying the low frequency signal supplied to the input terminal 30 to the non-inverting input terminal.
【００１０】演算増幅器３４の出力側と反転入力端子と
の間には、直列に接続された抵抗器３８、４０が接続さ
れている。これら抵抗器３８、４０としては、例えば抵
抗値Ｒｆ１、Ｒｆ２が１ＭΩのものが使用されている。The resistors 38 and 40 connected in series are connected between the output side of the operational amplifier 34 and the inverting input terminal. As the resistors 38 and 40, for example, resistors having resistance values Rf1 and Rf2 of 1 MΩ are used.
【００１１】抵抗器３８、４０の相互接続点と基準電位
点との間には、抵抗器４２とコンデンサ４４の直列回路
が接続されている。抵抗器４２としては例えば抵抗値Ｒ
ｓ１が１１０ＫΩのものを使用し、コンデンサ４４とし
ては例えば容量Ｃｓ１が０．１μＦのものが使用されて
いる。A series circuit of a resistor 42 and a capacitor 44 is connected between an interconnection point of the resistors 38 and 40 and a reference potential point. As the resistor 42, for example, a resistance value R
A capacitor having a capacitance Cs1 of 0.1 μF is used as the capacitor 44, for example.
【００１２】また、演算増幅器３４の反転入力端子と基
準電位点との間には、抵抗器４６とコンデンサ４８との
直列回路が接続されている。抵抗器４６としては、抵抗
器４２と同様に抵抗値Ｒｓ２が１１０ＫΩのものを使用
し、コンデンサ４８としては、コンデンサ４４と同様に
容量Ｃｓ２が０．１μＦのものを使用している。A series circuit of a resistor 46 and a capacitor 48 is connected between the inverting input terminal of the operational amplifier 34 and a reference potential point. A resistor having a resistance value Rs2 of 110 KΩ is used as the resistor, and a capacitor having a capacitance Cs2 of 0.1 μF is used as the capacitor.
【００１３】演算増幅器３４の出力側は、交流結合用の
コンデンサ５０を介して出力端子５２に接続されてい
る。The output side of the operational amplifier 34 is connected to an output terminal 52 via a capacitor 50 for AC coupling.
【００１４】このように構成された非反転増幅器では、
演算増幅器３４の反転入力端子と非反転入力端子との間
に、イマジナリショートが成立するので、入力端子３０
の電圧Ｖｉと、出力端子５２の電圧Ｖｏとの間には、数
１の関係が成立する。In the non-inverting amplifier configured as described above,
Since an imaginary short is established between the inverting input terminal and the non-inverting input terminal of the operational amplifier 34, the input terminal 30
And the voltage Vo at the output terminal 52 have the relationship of Equation 1.
【００１５】[0015]
【数１】 (Equation 1)
【００１６】数１より、この非反転増幅器の電圧ゲイン
は数２によって表される。From equation (1), the voltage gain of this non-inverting amplifier is expressed by equation (2).
【００１７】[0017]
【数２】 (Equation 2)
【００１８】ここで上述したようにＲｆ１、Ｒｆ２は１
ＭΩ、Ｒｓ１、Ｒｓ２は１１０ＫΩであるので、この実
施例の非反転増幅器の電圧ゲインは約１０１．８とな
り、従来のものとほぼ同等である。As described above, Rf1 and Rf2 are 1
Since MΩ, Rs1, and Rs2 are 110 KΩ, the voltage gain of the non-inverting amplifier of this embodiment is about 101.8, which is almost the same as the conventional one.
【００１９】また、この非反転増幅器の低域遮断周波数
は、１／〔２π（Ｒｆ１・Ｒｆ２）1/2 （Ｃｓ１・Ｃｓ
２）1/2 〕で表されるので、約１４．５Ｈｚとなり、上
述した従来のものとほぼ同様になる。即ち、従来のもの
よりも、小さな容量のコンデンサ４４、４８を使用しな
がら、従来のものと同等な低域遮断周波数特性を得てい
る。The low cutoff frequency of this non-inverting amplifier is 1 / [2π (Rf1 · Rf2) 1/2 (Cs1 · Cs
2) 1/2 ], it is about 14.5 Hz, which is almost the same as the conventional one described above. That is, the low cut-off frequency characteristic equivalent to that of the conventional one is obtained while using the capacitors 44 and 48 having smaller capacities than the conventional one.
【００２０】しかも、この非反転増幅器では、抵抗器４
２、コンデンサ４４で１組、抵抗器４６、コンデンサ４
８で１組の合計２組の時定数回路を設けているので、２
次のフィルタを設けたのと等価であるので、低域遮断周
波数以下の周波数では、図２の従来のものでは６ｄＢ／
ｏｃｔのスロープであったものが、１２ｄＢ／ｏｃｔの
スロープとなり、従来のものよりも急峻となる。Moreover, in this non-inverting amplifier, the resistor 4
2. One set of capacitor 44, resistor 46, capacitor 4
8, two sets of time constant circuits are provided.
At a frequency lower than the low cut-off frequency, the conventional filter shown in FIG.
The oct slope becomes 12 dB / oct slope, which is steeper than the conventional one.
【００２１】上記の実施例では、抵抗器４２、４６にそ
れぞれコンデンサ４４、４８を設けたが、いずれか一方
のコンデンサを省略し、このコンデンサに接続されてい
る抵抗器を直接に接地してもよい。例えば、コンデンサ
４４を省略し、抵抗器４２を直接に接地してもよい。こ
の場合、出力側に生じるオフセット電圧は、直流に対す
る電圧ゲインが、〔１＋（１ＭΩ＋１１０ＫΩ／１１０
ＫΩ）〕で約１０倍となるので、約１０倍悪化する。し
かし、通常、直流ゲインが１０倍程度では、オフセット
電圧は実用上問題にならないので、コンデンサ４４、４
８のいずれかを省略することは可能である。この場合、
低域遮断周波数以下の周波数でのスロープは６ｄＢ／ｏ
ｃｔとなる。In the above embodiment, the capacitors 44 and 48 are provided for the resistors 42 and 46, respectively. However, one of the capacitors may be omitted and the resistor connected to this capacitor may be directly grounded. Good. For example, the capacitor 44 may be omitted and the resistor 42 may be directly grounded. In this case, the offset voltage generated on the output side has a voltage gain with respect to DC of [1+ (1 MΩ + 110 KΩ / 110).
KΩ)], which is about 10 times, which is about 10 times worse. However, usually, when the DC gain is about 10 times, the offset voltage is not a problem in practical use.
8 can be omitted. in this case,
The slope at frequencies below the low cut-off frequency is 6 dB / o
ct.
【００２２】但し、図２に示したものと比較して、部品
の増加は１ＭΩの抵抗器、例えば抵抗器３８と、１１０
ＫΩの抵抗器、例えば抵抗器４２だけであるので、製造
は容易となる。However, as compared with the one shown in FIG. 2, the number of components is increased by a resistor of 1 MΩ, for example, the resistors 38 and 110.
Since only a resistor of KΩ, for example, the resistor 42, is used, manufacturing is easy.
【００２３】上記の実施例では、演算増幅器３４の出力
側と反転入力端子との間に、直列に２本の抵抗器３８、
４０を接続したが、この抵抗器の数は２以上とすること
が可能である。無論、この場合、これら抵抗器の相互接
続点と接地電位点との間に、抵抗器４２と同様な抵抗器
と、コンデンサ４４と同様なコンデンサとの直列回路を
接続するか、或いは抵抗器４２と同様な抵抗器を単独で
接続する。In the above embodiment, two resistors 38 are connected in series between the output side of the operational amplifier 34 and the inverting input terminal.
Although 40 were connected, the number of resistors could be two or more. Of course, in this case, a series circuit of a resistor similar to the resistor 42 and a capacitor similar to the capacitor 44 is connected between the interconnection point of these resistors and the ground potential, or Connect the same resistor as above.
【００２４】[0024]
【発明の効果】以上のように、本発明によれば、複数の
第１の抵抗器を直列に演算増幅器の出力側と反転入力端
子との間に接続しており、複数の第２の抵抗器を反転入
力端子と基準電位点との間、及び各第１の抵抗器の接続
点と基準電位点との間に接続しているので、従来のもの
とほぼ同一の利得を得ようとする場合、各第１の抵抗器
の抵抗値と第２の抵抗器の抵抗値との比率を、従来の反
転入力端子と基準電位点との間に接続されていた１つの
抵抗器の抵抗値と、演算増幅器の出力側と反転入力端子
との間に接続されていた１つの抵抗器の抵抗値の比率よ
り小さくすることができる。よって、第２の抵抗器の抵
抗値を、従来の反転入力端子と基準電位点との間に接続
されていた１つの抵抗器の抵抗値よりも大きくすること
が可能となり、従来のものと同様な低域遮断周波数とす
れば、各第２の抵抗器と直列に接続されるコンデンサ
も、容量を従来のもののコンデンサよりも小さくするこ
とができる。容量の小さいコンデンサの方が容量の大き
いコンデンサよりも価格は安いので、この非反転増幅器
を安価に製造することができる。しかも、容量の小さい
コンデンサの方が、高精度のものも存在するので、それ
らを用いれば、この非反転増幅器を量産した場合でも、
低域遮断周波数のばらつきを小さくできる。さらに、各
第２の抵抗器それぞれと直列にコンデンサを接続してい
るので、直流成分が基準電位点に流れることが全くな
く、オフセット電圧の利得を１とすることができ、オフ
セット電圧を実質的に除去することができる。As described above, according to the present invention, the plurality of first resistors are connected in series between the output side of the operational amplifier and the inverting input terminal, and the plurality of second resistors are connected in series. Are connected between the inverting input terminal and the reference potential point, and between the connection point of each first resistor and the reference potential point, so as to obtain almost the same gain as the conventional one. In this case, the ratio between the resistance value of each first resistor and the resistance value of the second resistor is calculated by using the resistance value of one resistor connected between the conventional inverting input terminal and the reference potential point. The ratio of the resistance of one resistor connected between the output side of the operational amplifier and the inverting input terminal can be made smaller. Therefore, the resistance value of the second resistor can be made larger than the resistance value of one resistor connected between the conventional inverting input terminal and the reference potential point. With a low cut-off frequency, the capacitors connected in series with the respective second resistors can also have a smaller capacity than conventional capacitors. Since a capacitor having a small capacity is cheaper than a capacitor having a large capacity, the non-inverting amplifier can be manufactured at low cost. In addition, some capacitors with smaller capacitance have higher precision, so if they are used, even if this non-inverting amplifier is mass-produced,
Variations in the low-frequency cutoff frequency can be reduced. Further, since a capacitor is connected in series with each of the second resistors, a DC component does not flow to the reference potential point at all, the gain of the offset voltage can be set to 1, and the offset voltage can be substantially reduced. Can be removed.
【００２５】また、各第２の抵抗器にそれぞれコンデン
サを直列に接続しているので、この非反転増幅器の低域
遮断周波数以下の周波数でのスロープを急峻にすること
ができる。Further, since a capacitor is connected in series to each of the second resistors, the slope of the non-inverting amplifier at a frequency lower than the low cutoff frequency can be made steep.
【図１】本発明による非反転増幅器の１実施例の回路図
である。FIG. 1 is a circuit diagram of one embodiment of a non-inverting amplifier according to the present invention.
【図２】従来の非反転増幅器の一例の回路図である。FIG. 2 is a circuit diagram of an example of a conventional non-inverting amplifier.
３４ 演算増幅器 ３８ ４０ （第１の）抵抗器 ４２ ４６ （第２の）抵抗器 ４４ ４８ コンデンサ 34 operational amplifier 38 40 (first) resistor 42 46 (second) resistor 44 48 capacitor
Claims (1)
演算増幅器と、この演算増幅器の反転入力端子と出力端
子との間に直列に接続された複数の第１の抵抗器と、上
記反転入力端子と基準電位点との間及び各第１の抵抗器
の接続点と上記基準電位点との間にそれぞれ接続された
上記各第１の抵抗器よりも値の小さい複数の第２の抵抗
器とを、具備し、第１及び第２の抵抗器を１つずつ設け
たときに所定の利得を得るために必要な両抵抗値の比率
よりも、前記所定の利得を得るために設定された互いに
対応する各第１及び第２の抵抗器の抵抗値の比率が小さ
く、これら第２の抵抗器と直列にそれぞれコンデンサを
接続してなることを特徴とする非反転増幅器。An operational amplifier to which an input signal is supplied to a non-inverting input terminal; a plurality of first resistors connected in series between an inverting input terminal and an output terminal of the operational amplifier; A plurality of second resistors each having a smaller value than each of the first resistors connected between the input terminal and the reference potential point and between the connection point of each first resistor and the reference potential point, respectively. A first resistor and a second resistor, each of which is set to obtain the predetermined gain rather than the ratio of the two resistance values required to obtain the predetermined gain when the first and second resistors are provided one by one. A ratio of the resistance value of each of the first and second resistors corresponding to each other is small, and a capacitor is connected in series with each of the second resistors.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24263592A JP3166879B2 (en) | 1992-08-18 | 1992-08-18 | Non-inverting amplifier |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP24263592A JP3166879B2 (en) | 1992-08-18 | 1992-08-18 | Non-inverting amplifier |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH0669733A JPH0669733A (en) | 1994-03-11 |
| JP3166879B2 true JP3166879B2 (en) | 2001-05-14 |
Family
ID=17091989
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP24263592A Expired - Fee Related JP3166879B2 (en) | 1992-08-18 | 1992-08-18 | Non-inverting amplifier |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3166879B2 (en) |
Families Citing this family (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP5088099B2 (en) * | 2007-11-07 | 2012-12-05 | ミツミ電機株式会社 | Video signal amplifier circuit and semiconductor integrated circuit for amplification |
-
1992
- 1992-08-18 JP JP24263592A patent/JP3166879B2/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| JPH0669733A (en) | 1994-03-11 |
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