JPH0435015B2 - - Google Patents
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- Publication number
- JPH0435015B2 JPH0435015B2 JP60107301A JP10730185A JPH0435015B2 JP H0435015 B2 JPH0435015 B2 JP H0435015B2 JP 60107301 A JP60107301 A JP 60107301A JP 10730185 A JP10730185 A JP 10730185A JP H0435015 B2 JPH0435015 B2 JP H0435015B2
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- Prior art keywords
- resistor
- variable
- resistance
- amplifier
- fixed
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Description
【発明の詳細な説明】
産業上の利用分野
本発明は、低電流の電流−電圧変換回路、特に
フオト・ダイオードなどの光電素子を用いた測光
回路に関するものである。DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a low current current-to-voltage conversion circuit, and particularly to a photometric circuit using a photoelectric element such as a photodiode.
従来の技術
近年、光計測の分野においては、微弱光の計測
が要求されてきており、光電素子の低光電流域を
精度良く測定することが必要となつてきている。
また、広いダイナミツクレンジを持つ光電素子、
例えば、フオト・ダイオードは数pAから数＋μA
のダイナミツクレンジを持つており、これを有効
に利用するためにも、光電素子の低光電流域の計
測が必要となつてきている。BACKGROUND ART In recent years, in the field of optical measurement, there has been a demand for measurement of weak light, and it has become necessary to accurately measure the low photocurrent region of photoelectric elements.
In addition, photoelectric elements with a wide dynamic range,
For example, a photo diode has a power of several pA to several + μA.
In order to make effective use of this dynamic range, it has become necessary to measure the low photocurrent range of photoelectric devices.
フオト・ダイオードを用いた従来の測光回路
は、第３図に示すような回路で実現されてきた。
この回路では、帰還抵抗２２を切換手段２３で切
換え、回路の増幅度を変えて光電素子１の広いダ
イナミツクレンジに対応させている。しかしなが
ら、切換手段２３は、リレーやスイツチなど漏れ
電流が光電流より少ないものでなければ、光電素
子１の低光電流域において測定に誤差が生じる。
このため、切換手段２３には、リレーやスイツチ
が用いられるが、応答性が悪いことや消費電力が
大きいため電地駆動の測光器等への応用が困難で
あるなどの問題があつた。 A conventional photometric circuit using a photo diode has been realized with a circuit as shown in FIG.
In this circuit, the feedback resistor 22 is switched by the switching means 23, and the amplification degree of the circuit is changed to correspond to the wide dynamic range of the photoelectric element 1. However, unless the switching means 23 is a relay or switch whose leakage current is smaller than the photocurrent, an error will occur in the measurement in the low photocurrent range of the photoelectric element 1.
For this reason, relays and switches are used as the switching means 23, but these have problems such as poor responsiveness and high power consumption, making it difficult to apply them to electrically driven photometers and the like.
また、第４図に示すように、電池駆動の測光器
等への応用できる回路も考案されている（特公昭
58−37489号公報）。しかし、この回路では、
FET２５の漏れ電流がフオトダイオード１の光
電流と同程度の数百pAのがあり、フオトダイオ
ード１の低光電流域での使用ができない。 Additionally, as shown in Figure 4, a circuit has been devised that can be applied to battery-powered photometers, etc.
58-37489). However, in this circuit,
The leakage current of FET 25 is several hundred pA, which is about the same as the photocurrent of photodiode 1, and photodiode 1 cannot be used in the low photocurrent range.
演算増幅器を用いた増幅回路としては、例えば
実開昭53−163186号公報のように、演算増幅器の
出力を抵抗分割し、その分割点か出力電圧を帰還
させることにより、大きな増幅度を得るものがあ
る。このような方法で増幅度を変化させるために
は、抵抗分割比を変化させて帰還量を変える必要
がある。このため、前述のリレーやスイツチを使
用する必要があり、電池駆動のように低消費電力
動作には対応できない。 An example of an amplifier circuit using an operational amplifier is one that obtains a large degree of amplification by dividing the output of the operational amplifier with resistance and feeding back the output voltage at the dividing point, as shown in Japanese Utility Model Application Publication No. 53-163186. There is. In order to change the degree of amplification using such a method, it is necessary to change the amount of feedback by changing the resistance division ratio. Therefore, it is necessary to use the aforementioned relays and switches, and it cannot support low power consumption operation like battery drive.
発明が解決しようとする問題点
このような従来の回路では、リレーやスイツチ
を用いなければならないため、低消費電力が実現
できず電池駆動の測光器等に応用が困難である。
また、FETを用いた前述の回路では、FETの漏
れ電流が大きく、光電素子の低光電流域での使用
が困難になり、光電素子本来の広いダイナミツク
レンジが使用できない。Problems to be Solved by the Invention Since such conventional circuits require the use of relays and switches, low power consumption cannot be achieved and it is difficult to apply them to battery-powered photometers and the like.
Furthermore, in the above-mentioned circuit using an FET, the leakage current of the FET is large, making it difficult to use a photoelectric element in a low photocurrent range, and making it impossible to use the wide dynamic range inherent to a photoelectric element.
本発明はかかる点に鑑みてなされたもので、光
電素子の低光電流域からの広いダイナミツクレン
ジと、低消費電力を実現して、電池駆動の測光器
等への応用可能な測光回路を提供するものであ
る。 The present invention has been made in view of these points, and provides a photometry circuit that achieves a wide dynamic range from the low photocurrent range of photoelectric elements and low power consumption, and is applicable to battery-powered photometers, etc. It is something to do.
問題点を解決するための手段
本発明は、上記問題点を解決するため、光電素
子からの光電流を増幅する増幅器と、この増幅器
負帰還抵抗と、この負帰還抵抗による帰還量を変
化させる抵抗値の可変手段を有する可変抵抗部
と、この可変抵抗部と直列に接続し他端を接地し
た第一の固定抵抗と、可変抵抗部に並列に接続し
た第二の固定抵抗とを備え、帰還抵抗を可変抵抗
部と第一の固定抵抗の接続点に接続するとともに
可変抵抗部の可変手段による抵抗値の最大値より
第二の固定抵抗の抵抗値を小さくして、可変抵抗
部の可変手段を制御手段により増幅器の出力に応
じて制御し、回路の増幅度を変化させて出力を得
るものである。Means for Solving the Problems In order to solve the above problems, the present invention provides an amplifier that amplifies the photocurrent from a photoelectric element, a negative feedback resistor for this amplifier, and a resistor that changes the amount of feedback by the negative feedback resistor. A variable resistor having a value variable means, a first fixed resistor connected in series with the variable resistor and having the other end grounded, and a second fixed resistor connected in parallel to the variable resistor. A resistor is connected to a connection point between the variable resistance section and the first fixed resistor, and the resistance value of the second fixed resistor is made smaller than the maximum value of the resistance value by the variable means of the variable resistance section. is controlled by the control means according to the output of the amplifier, and the amplification degree of the circuit is changed to obtain the output.
作 用
本発明は上記した構成により、増幅器の負帰還
系の帰還量を可変抵抗部の可変手段を、増幅器の
出力に応じて制御手段により制御することで回路
系の増幅度を変え、光電素子の低光電流域からの
広いダイナミツクレンジを有効に活用することが
できるものである。また、可変手段により可変抵
抗部が最大の抵抗値になつたときの抵抗値が並列
に接続された第二の固定抵抗の抵抗値より大きい
ので、第二の固定抵抗に流れる電流が支配的とな
り可変抵抗部にFETなどを用いた場合の漏れ電
流の影響を少なくすることができ、精度が良くし
かもダイナミツクレンジの広い測光回路が得られ
る。According to the above-described configuration, the present invention changes the amplification degree of the circuit system by controlling the feedback amount of the negative feedback system of the amplifier by the control means of the variable resistor section in accordance with the output of the amplifier, and The wide dynamic range from the low photocurrent range can be effectively utilized. Furthermore, since the resistance value when the variable resistance section reaches its maximum resistance value due to the variable means is greater than the resistance value of the second fixed resistor connected in parallel, the current flowing through the second fixed resistor becomes dominant. It is possible to reduce the influence of leakage current when a FET or the like is used in the variable resistance section, and a photometric circuit with good accuracy and a wide dynamic range can be obtained.
実施例
第１図は本発明の測光回路の一実施例を示し、
増幅器として演算増幅器を用いたものである。第
１図において、１はフオトダイオードなどの光電
素子、２は演算増幅器、３は帰還抵抗、４は第一
の固定抵抗としての固定抵抗Ａ，５は可変抵抗
部、６は可変抵抗部５の可変手段としてのFET、
７はFET６を制御する制御手段としての制御回
路、８は出力、９は制御回路入力、１０は固定抵
抗Ｂ、１１は第二の固定抵抗としての固定抵抗Ｃ
であり、可変抵抗部５はFET６，固定抵抗Ｂ１
０から構成する。Embodiment FIG. 1 shows an embodiment of the photometric circuit of the present invention,
This uses an operational amplifier as an amplifier. In FIG. 1, 1 is a photoelectric element such as a photodiode, 2 is an operational amplifier, 3 is a feedback resistor, 4 is a fixed resistor A as a first fixed resistor, 5 is a variable resistor section, and 6 is a variable resistor section 5. FET as variable means,
7 is a control circuit as a control means for controlling the FET 6, 8 is an output, 9 is a control circuit input, 10 is a fixed resistor B, and 11 is a fixed resistor C as a second fixed resistor.
The variable resistance section 5 includes an FET 6 and a fixed resistance B1.
Configure from 0.
以上のように構成された本実施例の測光回路に
ついて、以下その動作を説明する。 The operation of the photometric circuit of this embodiment configured as described above will be described below.
フオトダイオードなどの光電素子１に光が入射
すると、入射した光量に応じた光電流が発生す
る。この光電流は演算増幅器２に入力され、光電
流は増幅・電圧値に変換される。このとき、増幅
度は帰還抵抗３によつて帰還される帰還量によつ
て決まる。演算増幅器２の出力８は、固定抵抗Ａ
４と可変抵抗部５とで分圧される。ここで、可変
抵抗部５を構成するFET６と固定抵抗Ｂ１０は
直列に接続する。 When light is incident on a photoelectric element 1 such as a photodiode, a photocurrent is generated depending on the amount of incident light. This photocurrent is input to an operational amplifier 2, where the photocurrent is amplified and converted into a voltage value. At this time, the degree of amplification is determined by the amount of feedback fed back by the feedback resistor 3. The output 8 of the operational amplifier 2 is a fixed resistor A.
4 and the variable resistance section 5. Here, the FET 6 and the fixed resistor B10 constituting the variable resistance section 5 are connected in series.
また、固定抵抗Ｃ１１は前述のFET６と固定抵
抗Ｂ１０との直列回路と並列に接続される。固定
抵抗Ａ４と可変抵抗部５とで分圧された演算増幅
器２の出力を帰還抵抗３を介して演算増幅器２の
負入力に帰還させるとともに、可変抵抗部５の抵
抗値を変えて、固定抵抗Ａ４と可変抵抗部５との
分圧比を変えることによつて帰還量を変えること
ができる。すなわち、FET６をアナログ・スイ
ツチとして動作させれば帰還抵抗３への帰還量が
変化する。Further, the fixed resistor C11 is connected in parallel with the series circuit of the FET 6 and the fixed resistor B10 described above. The output of the operational amplifier 2 divided by the fixed resistor A4 and the variable resistor 5 is fed back to the negative input of the operational amplifier 2 via the feedback resistor 3, and the resistance value of the variable resistor 5 is changed to By changing the voltage division ratio between A4 and variable resistor section 5, the amount of feedback can be changed. That is, if the FET 6 is operated as an analog switch, the amount of feedback to the feedback resistor 3 changes.
ここで、FET６を中心とする回路の動作をさ
らに詳しく説明する。 Here, the operation of the circuit centering on the FET 6 will be explained in more detail.
演算増幅器２の出力を出力電圧の下限値VLか
ら出力電圧の上限値VHの範囲とする（演算増幅
器２のダイナミツクレンジは光電素子１のそれに
比べて小さいので増幅度を変えてこれに対応する
ため出力電圧の上限・下限を定める）ため、制御
回路７でVL，VHを検出し、これに基づいてFET
６の導通状態を制御する。例えば、制御回路７は
第２図に示す回路で実現できる。固定抵抗B10お
よび固定抵抗Ｃ１１は、固定抵抗Ｂ１０《固定抵
抗Ｃ１１の関係があるとする。今、FET６が非
導通であるとする。このとき、帰還抵抗３を介し
て帰還される帰還量は固定抵抗Ａ４と固定抵抗Ｃ
１１との比で決まる。ここで、演算増幅器２の出
力が上限値VHを超えると、制御回路７はFET６
を導通にする。すると帰還量は固定抵抗Ａ４と固
定抵抗Ｂ１０との比で決まる（固定抵抗Ｂ１０
《固定抵抗Ｃ１１であるから固定抵抗Ｃ１１は無
視できる。）ので、帰還量は大きくなる（固定抵
抗Ｂ１０《固定抵抗Ｃ１１のため）。したがつて、
増幅度は小さくなるから演算増幅器２の出力は上
限値VGHより小さくなる。 The output of the operational amplifier 2 is set within the range from the lower limit value V L of the output voltage to the upper limit value V H of the output voltage (the dynamic range of the operational amplifier 2 is smaller than that of the photoelectric element 1, so the amplification degree is changed to (in order to set the upper and lower limits of the output voltage), the control circuit 7 detects V L and V H , and based on this, the FET
Controls the conduction state of 6. For example, the control circuit 7 can be realized by the circuit shown in FIG. It is assumed that the fixed resistance B10 and the fixed resistance C11 have a relationship of fixed resistance B10<<fixed resistance C11. Now assume that FET6 is non-conducting. At this time, the amount of feedback fed back via the feedback resistor 3 is the fixed resistor A4 and the fixed resistor C.
It is determined by the ratio to 11. Here, when the output of the operational amplifier 2 exceeds the upper limit value VH , the control circuit 7
Make it conductive. Then, the amount of feedback is determined by the ratio of fixed resistance A4 and fixed resistance B10 (fixed resistance B10
<<Since it is a fixed resistance C11, the fixed resistance C11 can be ignored. ), the amount of feedback becomes large (because of the fixed resistor B10 (fixed resistor C11)). Therefore,
Since the degree of amplification becomes smaller, the output of the operational amplifier 2 becomes smaller than the upper limit value VGH .
また、演算増幅器２の出力が下限値VLより小
さくなつたときは上述の動作が逆に起こる。 Furthermore, when the output of the operational amplifier 2 becomes smaller than the lower limit value V L , the above operation occurs in reverse.
なお、この測光回路ではFET６が非導通であ
るときに流れる漏れ電流よりも固定抵抗Ｃ１１に
流れる電流が十分大きくなるように設定すれば、
FETの漏れ電流は無視でき、測定精度に影響し
ない。 In addition, in this photometric circuit, if the current flowing through the fixed resistor C11 is set to be sufficiently larger than the leakage current flowing when FET6 is non-conducting,
FET leakage current is negligible and does not affect measurement accuracy.
以上のように、本実施例によれば、光電素子１
からの光電流を演算増幅器２に供給し、演算増幅
器出力端に一端を接続し、演算増幅器出力で
FET６をON／OFFさせて抵抗値を変化させる可
変抵抗部５と、この可変抵抗部５の他端に一端を
接続し他端を接地した固定抵抗Ａ４と、可変抵抗
部５と固定抵抗Ａ４の接続点から演算増幅器負入
力に接続して負帰還をかける帰還抵抗３とを設
け、可変抵抗部５のFET６に並列に接続した固
定抵抗Ｃ１１に、FET６の漏れ電流よりも大き
な電流を定常的に流すことにより、FET６の
ON／OFF動作時にFET６の漏れ電流による演算
増幅器２の帰還量変化をなくし、増幅度を切り換
えて演算増幅器２のダイナミツクレンジを超えて
安定な光計測ができる。 As described above, according to this embodiment, the photoelectric element 1
The photocurrent from is supplied to operational amplifier 2, one end is connected to the operational amplifier output terminal, and the operational amplifier output is
A variable resistance section 5 that changes the resistance value by turning the FET 6 ON/OFF, a fixed resistance A4 whose one end is connected to the other end of the variable resistance section 5 and the other end grounded, and a variable resistance section 5 and a fixed resistance A4. A feedback resistor 3 is provided which is connected to the negative input of the operational amplifier from the connection point to apply negative feedback, and a current larger than the leakage current of FET 6 is constantly applied to the fixed resistor C11 connected in parallel to FET 6 of the variable resistance section 5. By flowing, FET6
During ON/OFF operation, changes in the feedback amount of the operational amplifier 2 due to the leakage current of the FET 6 are eliminated, and by switching the amplification degree, stable optical measurement can be performed exceeding the dynamic range of the operational amplifier 2.
なお、本実施例において、固定抵抗Ｃ１１に直
列にFETを接続して同様の動作をさせることが
できる。またFET1つの場合について説明した
が、複数のFETを設けることで、３段階以上の
増幅度の切換えができることは言うまでもない。
さらに帰還抵抗に並列に帰還容量を設けて演算増
幅器２の動作の安定を図ることは言うまでもな
い。 Note that in this embodiment, a similar operation can be performed by connecting an FET in series with the fixed resistor C11. Further, although the case of one FET has been described, it goes without saying that by providing a plurality of FETs, it is possible to switch the amplification degree in three or more stages.
Furthermore, it goes without saying that a feedback capacitor is provided in parallel with the feedback resistor to stabilize the operation of the operational amplifier 2.
発明の効果
本発明の測光回路は、光電素子と、光電素子か
らの光電流を増幅する増幅器と、増幅器出力端に
一端を接続し、増幅器出力に応じて可変手段を制
御手段で制御して抵抗値を変化させる可変抵抗部
と、この可変抵抗部の他端に一端を接続し、他端
を接地した第一の固定抵抗と、可変抵抗部と第一
の固定抵抗の接続点から増幅器の入力に接続した
負帰還抵抗を設け、可変抵抗部に並列に接続した
第二の固定抵抗にFETなどの可変手段の漏れ電
流よりも大きな電流を通常的に流すことにより、
FETの漏れ電流が光電流計測に影響しないよう
にして、光電素子の低光電流からの広いダイナミ
ツクレンジを活用しながら電池駆動ができ、その
実用効果は大きい。Effects of the Invention The photometric circuit of the present invention includes a photoelectric element, an amplifier that amplifies the photocurrent from the photoelectric element, one end of which is connected to the output terminal of the amplifier, and a variable means that is controlled by a control means according to the output of the amplifier. A variable resistor that changes the value, a first fixed resistor whose one end is connected to the other end of the variable resistor, and whose other end is grounded, and an amplifier input from the connection point of the variable resistor and the first fixed resistor. By providing a negative feedback resistor connected to the variable resistor, and normally passing a current larger than the leakage current of the variable means such as FET through the second fixed resistor connected in parallel to the variable resistor,
By preventing the leakage current of the FET from affecting photocurrent measurement, battery power can be utilized while utilizing the photoelectric element's wide dynamic range from low photocurrent, which has great practical effects.
第１図は本発明の実施例における測光回路を示
した図、第２図はその制御回路の一構成例を示し
た図、第３図及び第４図は従来の測光回路の一例
を示した図である。
１……光電素子、２……演算増幅器、３……帰
還抵抗、４……固定抵抗Ａ、５……可変抵抗部、
６……FET、７……制御回路、１０……固定抵
抗Ｂ、１１……固定抵抗Ｃ。
FIG. 1 is a diagram showing a photometric circuit in an embodiment of the present invention, FIG. 2 is a diagram showing an example of the configuration of the control circuit, and FIGS. 3 and 4 are examples of conventional photometric circuits. It is a diagram. 1... Photoelectric element, 2... Operational amplifier, 3... Feedback resistor, 4... Fixed resistance A, 5... Variable resistance section,
6...FET, 7...Control circuit, 10...Fixed resistor B, 11...Fixed resistor C.
Claims (1)
る増幅器と、一端を前記増幅器の出力端に接続し
た抵抗値の可変手段を有する可変抵抗部と、この
可変抵抗部と直列に接続し他端を接地した第一の
固定抵抗と、前記可変抵抗部に並列に接続した第
二の固定抵抗と、前記可変抵抗部と前記第一の固
定抵抗の中点から前記増幅器の入力へ負帰還させ
る帰還抵抗とを具備し、前記可変抵抗部の可変手
段による抵抗値の最大値より前記第二の固定抵抗
の抵抗値を小さくするとともに、前記増幅器の出
力に応じて前記可変手段を制御する制御手段を有
する測光回路。1. A photoelectric element, an amplifier for amplifying the photocurrent of the photoelectric element, a variable resistance section having a resistance variable means whose one end is connected to the output terminal of the amplifier, and the other end connected in series with the variable resistance section. a first fixed resistor that is grounded, a second fixed resistor that is connected in parallel to the variable resistor, and feedback that provides negative feedback from the midpoint between the variable resistor and the first fixed resistor to the input of the amplifier. and control means for controlling the variable means in accordance with the output of the amplifier, the resistance value of the second fixed resistor being smaller than the maximum value of the resistance value by the variable means of the variable resistance section. A photometric circuit with.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60107301A JPS61265536A (en) | 1985-05-20 | 1985-05-20 | Photometric circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP60107301A JPS61265536A (en) | 1985-05-20 | 1985-05-20 | Photometric circuit |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPS61265536A JPS61265536A (en) | 1986-11-25 |
| JPH0435015B2 true JPH0435015B2 (en) | 1992-06-09 |
Family
ID=14455621
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP60107301A Granted JPS61265536A (en) | 1985-05-20 | 1985-05-20 | Photometric circuit |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPS61265536A (en) |
Family Cites Families (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS53163186U (en) * | 1977-05-27 | 1978-12-20 |
-
1985
- 1985-05-20 JP JP60107301A patent/JPS61265536A/en active Granted
Also Published As
| Publication number | Publication date |
|---|---|
| JPS61265536A (en) | 1986-11-25 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| EXPY | Cancellation because of completion of term |