JPH05322651A - Photodetector - Google Patents
PhotodetectorInfo
- Publication number
- JPH05322651A JPH05322651A JP13228192A JP13228192A JPH05322651A JP H05322651 A JPH05322651 A JP H05322651A JP 13228192 A JP13228192 A JP 13228192A JP 13228192 A JP13228192 A JP 13228192A JP H05322651 A JPH05322651 A JP H05322651A
- Authority
- JP
- Japan
- Prior art keywords
- current
- feedback
- photodetector
- resistors
- operational amplifier
- 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.)
- Granted
Links
Landscapes
- Photometry And Measurement Of Optical Pulse Characteristics (AREA)
Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、光検出器に関し、特に
液体クロマトグラフ用吸光度検出器等に好適に使用され
る光検出器の改良に関する。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photodetector, and more particularly to improvement of a photodetector which is preferably used as an absorbance detector for a liquid chromatograph.
【０００２】[0002]
【従来の技術】液体クロマトグラフ用吸光度検出器等に
使用される光検出器では、光を検知したホトダイオード
からの微小電流を、入力抵抗が非常に大きいオペアンプ
を使用した負帰還形の電流／電圧変換回路に入力して電
圧値に変換している。図２はこのような従来のオペアン
プ１１による負帰還形の電流／電圧変換回路１０を使用
した光検出器の構成例を示した図である。図において、
ホトダイオード１２が光を感知すると、感知した光の強
さに応じた微小電流ｉを出力する。この微小電流ｉは、
オペアンプ１１には入力抵抗が非常に大きいので流れ
ず、また、オペアンプ１１の反転入力端子１３の電位Ｖ
iはオペアンプ１１の非反転入力端子１４の電位Ｖg（＝
０Ｖ）と等しくなる。その為、オペアンプ１１の出力端
子１５の電位Ｖoは、上記の微小電流ｉによるオペアン
プ１１の出力端子１５と反転入力端子１３間の帰還抵抗
Ｒの降下電位−ｉＲとなり、上記の微小電流ｉに比例し
た電圧値が得られる。2. Description of the Related Art In a photodetector used for an absorbance detector for a liquid chromatograph, a small current from a photodiode that detects light is converted into a negative feedback type current / voltage using an operational amplifier with a very large input resistance. It is input to the conversion circuit and converted into a voltage value. FIG. 2 is a diagram showing a configuration example of a photodetector using the negative feedback type current / voltage conversion circuit 10 by such a conventional operational amplifier 11. In the figure,
When the photodiode 12 senses light, it outputs a minute current i corresponding to the sensed light intensity. This minute current i is
Since the input resistance is very large in the operational amplifier 11, it does not flow, and the potential V of the inverting input terminal 13 of the operational amplifier 11 does not flow.
i is the potential Vg of the non-inverting input terminal 14 of the operational amplifier 11 (=
0V). Therefore, the potential Vo of the output terminal 15 of the operational amplifier 11 becomes a drop potential -iR of the feedback resistance R between the output terminal 15 of the operational amplifier 11 and the inverting input terminal 13 due to the minute current i, which is proportional to the minute current i. The obtained voltage value is obtained.
【０００３】ところが、上記の帰還抵抗Ｒには数１０〜
数１００ＭΩの高い抵抗値が必要なので、従来は一般に
１個の金属系混合体皮膜抵抗（metal glazed film resi
stor）が使用されていたが、これにより発生する電流雑
音は大きく、上記の液体クロマトグラフ用吸光度検出器
等の検出感度を高める上で問題となっていた。However, the feedback resistor R has several tens of degrees.
Since a high resistance value of several 100 MΩ is required, conventionally one metal-based mixture film resistor (metal glazed film resist) is generally used.
Stor) was used, but the current noise generated by this was large, which was a problem in increasing the detection sensitivity of the above-mentioned absorbance detector for liquid chromatography.
【０００４】[0004]
【発明が解決しようとする課題】本発明は、上記事情に
鑑みてなされたものであり、オペアンプによる負帰還形
の電流／電圧変換回路の帰還抵抗により発生する電流雑
音を小さくすることによって検出感度を高めた、光検出
器を提供することを目的とする。SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and the detection sensitivity is reduced by reducing the current noise generated by the feedback resistor of the negative feedback type current / voltage conversion circuit by the operational amplifier. It is an object of the present invention to provide a photodetector having improved optical characteristics.
【０００５】[0005]
【課題を解決するための手段】本発明の光検出器では、
上記目的を達成するために、ホトダイオードからの微小
電流を、オペアンプを使用した負帰還形の電流／電圧変
換回路に入力して、電圧信号を取り出す光検出器におい
て、上記オペアンプの出力端子と反転入力端子間の帰還
抵抗として、複数の金属皮膜抵抗を直列に接続した構成
となっている。According to the photodetector of the present invention,
In order to achieve the above object, in a photodetector for extracting a voltage signal by inputting a minute current from a photodiode to a negative feedback type current / voltage conversion circuit using an operational amplifier, an output terminal of the operational amplifier and an inverting input A plurality of metal film resistors are connected in series as a feedback resistor between terminals.
【０００６】[0006]
【作用】本発明の光検出器では、帰還抵抗に複数（＝Ｎ
≧２）の抵抗を直列に接続して使用するので、Ｎ個の帰
還抵抗が例えば互いに等しいとすると、その各々の両端
にかかる電圧は、帰還抵抗が１個の場合に比べて１／Ｎ
となるが、抵抗に発生する電流雑音は、その抵抗の両端
にかかる電圧にほぼ比例するので、Ｎ個の帰還抵抗の各
々が発生する電流雑音も１／Ｎとなる。また、帰還抵抗
全体が発生する電流雑音は、各々の帰還抵抗が発生する
電流雑音の自乗の和の平方根となる。従って、帰還抵抗
にＮ個の抵抗を直列に接続して使用する場合に、帰還抵
抗全体が発生する電流雑音は、帰還抵抗を１個使用する
場合に比べて、１／Ｎの平方根倍となる。また、帰還抵
抗にＮ個の抵抗を直列に接続して使用するので、帰還抵
抗１個当りの抵抗値が小さくて済み、雑音特性に優れた
金属皮膜抵抗を使用出来、これによる雑音低減も期待出
来る。In the photodetector of the present invention, a plurality of feedback resistors (= N
Since ≧ 2) resistors are connected in series, if N feedback resistors are, for example, equal to each other, the voltage across each of them is 1 / N compared to the case where there is one feedback resistor.
However, since the current noise generated in the resistor is approximately proportional to the voltage applied across the resistor, the current noise generated in each of the N feedback resistors is also 1 / N. The current noise generated by all the feedback resistors is the square root of the sum of squares of the current noise generated by each feedback resistor. Therefore, when N resistors are connected in series to the feedback resistor and used, the current noise generated by the entire feedback resistor is 1 / N times the square root as compared with the case where one feedback resistor is used. .. Also, since N resistors are connected in series to the feedback resistor and used, the resistance value per feedback resistor can be small, and a metal film resistor with excellent noise characteristics can be used, and noise reduction by this is also expected. I can.
【０００７】[0007]
【実施例】図１は、本発明による光検出器１の一実施例
の構成例を示した図である。図１において、図２の従来
の構成例と異なるところは、オペアンプ１１の出力端子
１５と反転入力端子１３間の帰還抵抗Ｒが Ｒ＝Ｒ1＋Ｒ2＋Ｒ3＋・・・＋ＲN （Ｎ≧２） となるように Ｒ1，Ｒ2，Ｒ3，・・・ＲN に置き代わ
ったところである。FIG. 1 is a diagram showing a configuration example of an embodiment of a photodetector 1 according to the present invention. 1 is different from the conventional configuration example of FIG. 2 in that the feedback resistance R between the output terminal 15 and the inverting input terminal 13 of the operational amplifier 11 is R1 so that R = R1 + R2 + R3 + ... + RN (N ≧ 2). , R2, R3, ... RN have been replaced.
【０００８】図１ににおいて、ホトダイオード１２が感
知した光の強さに応じた微小電流ｉを出力すると、微小
電流ｉはオペアンプ１１には入力抵抗が非常に大きいの
で流れず、また、反転入力端子１３の電位Ｖiは非反転
入力端子１４の電位Ｖg（＝０Ｖ）と等しくなる。その
為、オペアンプ１１の出力端子１５の電位Ｖoは、上記
の微小電流ｉによる出力端子１５と反転入力端子１３間
の帰還抵抗Ｒ1，Ｒ2，Ｒ3，・・・，ＲNの降下電位 −ｉＲ1−ｉＲ2−ｉＲ3・・・−ＲN＝−ｉＲ となり、上記の微小電流ｉに比例した電圧値が得られ
る。In FIG. 1, when a small current i corresponding to the intensity of light sensed by the photodiode 12 is output, the minute current i does not flow to the operational amplifier 11 because its input resistance is very large, and the inverting input terminal The potential Vi of 13 becomes equal to the potential Vg (= 0V) of the non-inverting input terminal 14. Therefore, the potential Vo of the output terminal 15 of the operational amplifier 11 is the falling potential -iR1-iR2 of the feedback resistances R1, R2, R3, ..., RN between the output terminal 15 and the inverting input terminal 13 due to the minute current i. -IR3 ...- RN = -iR, and a voltage value proportional to the minute current i is obtained.
【０００９】この時、Ｎ個（Ｎ≧２）の帰還抵抗の各々
の両端にかかる電圧は、各々の帰還抵抗が互いに等しい
とすると、帰還抵抗が１個の場合に比べて１／Ｎとなる
が、抵抗に発生する電流雑音は、その抵抗の両端にかか
る電圧にほぼ比例する（ＪＩＳ Ｃ５２０２参照）の
で、Ｎ個の帰還抵抗の各々が発生する電流雑音も下記
（１）に示すように１／Ｎとなる。At this time, the voltage applied to both ends of each of the N feedback resistors (N ≧ 2) is 1 / N as compared with the case where one feedback resistor is provided, assuming that the feedback resistors are equal to each other. However, since the current noise generated in the resistor is almost proportional to the voltage applied across the resistor (see JIS C5202), the current noise generated in each of the N feedback resistors is also 1 as shown in (1) below. / N.
【００１０】また、Ｎ個の帰還抵抗の各々が発生する電
流雑音は互いに無相関であるので、下記（１）に示すよ
うに、帰還抵抗全体が発生する電流雑音は、各々の帰還
抵抗が発生する電流雑音の自乗の和の平方根となる。従
って、帰還抵抗にＮ個の抵抗を直列に接続して使用する
場合に、帰還抵抗全体が発生する電流雑音は、下記
（３）に示すように、帰還抵抗が１個の場合に比べて、
１／Ｎの平方根倍となる。Further, since the current noise generated by each of the N feedback resistors is uncorrelated with each other, the current noise generated by the entire feedback resistor is generated by each feedback resistor as shown in (1) below. Is the square root of the sum of the squares of the current noise. Therefore, when N resistors are connected in series to the feedback resistor and used, the current noise generated by the entire feedback resistor is, as shown in (3) below,
It is the square root times 1 / N.
【００１１】 √（Ｖ12＋Ｖ22＋・・・＋ＶN2)＝Ｖt （１） （Ｖ1，Ｖ2，・・・ＶN は抵抗Ｒ1，Ｒ2，・・・ＲNで
発生する電流雑音。Ｖt は帰還抵抗全体が発生する電流
雑音。） ここで Ｒ1＝Ｒ2＝・・・＝ＲN とすると Ｖ1＝Ｖ2＝・・・＝ＶN＝Ｖ／Ｎ （２） （Ｖは帰還抵抗にＲを１個使用した場合に、帰還抵抗Ｒ
で発生する電流雑音。） （１），（２）より Ｖt＝Ｖ√（１／Ｎ2＋１／Ｎ2・・・＋１／Ｎ2）＝Ｖ／√Ｎ （３） 具体例として、出力端子１５と反転入力端子１３間の帰
還抵抗に３０ＭΩが必要な場合に、１ＭΩの金属皮膜抵
抗３０個を直列に接続（Ｎ＝３０ ３０ＭΩ＝１ＭΩ×
３０）すると、帰還抵抗全体が発生する電流雑音は、帰
還抵抗が１個の場合に比べて、１／３０の平方根倍、つ
まり１／５程度に小さくなることが期待出来る。そのう
え、金属皮膜抵抗は雑音特性が優れている（発生する電
流雑音が小さい）ので、さらに、電流雑音の減少が期待
出来る。√ (V1 2 + V2 2 + ... + VN 2 ) = Vt (1) (V1, V2, ... VN are current noises generated by the resistors R1, R2, ... RN. Vt is a feedback resistance. Current noise generated as a whole.) Here, assuming that R1 = R2 = ... = RN, V1 = V2 = ... = VN = V / N (2) (V is the case where one R is used as a feedback resistor. And the feedback resistor R
Current noise generated in. ) From (1) and (2), Vt = V√ (1 / N 2 + 1 / N 2 ... + 1 / N 2 ) = V / √N (3) As a specific example, the output terminal 15 and the inverting input terminal 13 If 30 MΩ is required for the feedback resistance between them, 30 metal film resistors of 1 MΩ are connected in series (N = 30 30 MΩ = 1 MΩ ×
30) Then, the current noise generated by the entire feedback resistor can be expected to be reduced to 1/30 times the square root, that is, about 1/5 of that of the case where there is one feedback resistor. In addition, since the metal film resistor has excellent noise characteristics (generated current noise is small), further reduction of current noise can be expected.
【００１２】尚、上述の例では、帰還抵抗にＮ個の互い
に等しい抵抗を使用した場合について述べたが、そうで
ない場合（Ｎ個の必ずしも互いに等しくない抵抗を使用
した場合）に比べて、最も電流雑音の減少が期待出来
る。In the above example, the case where N equal resistors are used as the feedback resistors has been described, but compared with the case where N resistors are not necessarily used (when N resistors are not necessarily equal to each other), A reduction in current noise can be expected.
【００１３】[0013]
【発明の効果】本発明の光検出器によれば、帰還抵抗に
複数（＝Ｎ≧２）の抵抗を直列に接続して使用するの
で、帰還抵抗全体が発生する電流雑音は、帰還抵抗を１
個使用した場合に比べて、１／Ｎの平方根倍となり、大
幅に減少する。また、帰還抵抗にＮ個の抵抗を直列に接
続して使用するので、帰還抵抗１個当りの抵抗値が小さ
くて済む為、雑音特性に優れた金属皮膜抵抗を使用出
来、これによる雑音低減も期待出来る。According to the photodetector of the present invention, since a plurality of (= N ≧ 2) resistors are connected in series to the feedback resistor and used, current noise generated by the entire feedback resistor is caused by the feedback resistor. 1
Compared with the case where individual pieces are used, the square root becomes 1 / N times, which is a large reduction. Also, since N resistors are connected in series to the feedback resistor and used, the resistance value per feedback resistor can be small, so a metal film resistor with excellent noise characteristics can be used, and noise reduction by this is also possible. I can expect it.
【図１】本発明のオペアンプによる負帰還形の電流／電
圧変換回路を使用した光検出器の構成例図である。FIG. 1 is a structural example diagram of a photodetector using a negative feedback type current / voltage conversion circuit using an operational amplifier according to the present invention.
【図２】従来のオペアンプによる負帰還形の電流／電圧
変換回路を使用した光検出器の構成例図である。FIG. 2 is a diagram showing a configuration example of a photodetector using a negative feedback type current / voltage conversion circuit using a conventional operational amplifier.
１・・・光検出器 １１・・・オペアンプ １２・・・ホトダイオード １３・・・オペアンプの反転入力端子 １４・・・オペアンプの非反転入力端子 １５・・・オペアンプの出力端子 ｉ・・・ホトダイオードの出力電流 Ｒ1，Ｒ2，‥‥‥ＲN，Ｒ・・・帰還抵抗 DESCRIPTION OF SYMBOLS 1 ... Photodetector 11 ... Operational amplifier 12 ... Photodiode 13 ... Inversion input terminal of operational amplifier 14 ... Non-inverting input terminal of operational amplifier 15 ... Output terminal of operational amplifier i ... Operation of photodiode Output current R1, R2, ... RN, R ... Feedback resistance
Claims (1)
ンプを使用した負帰還形の電流／電圧変換回路に入力し
て、電圧信号を取り出す光検出器において、上記オペア
ンプの出力端子と反転入力端子間の帰還抵抗として、複
数の金属皮膜抵抗を直列に接続したことを特徴とする光
検出器。1. A photodetector for extracting a voltage signal by inputting a minute current from a photodiode to a negative feedback type current / voltage conversion circuit using an operational amplifier, between the output terminal and the inverting input terminal of the operational amplifier. A photodetector characterized in that a plurality of metal film resistors are connected in series as feedback resistors.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4132281A JP3005970B2 (en) | 1992-05-25 | 1992-05-25 | Photo detector |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP4132281A JP3005970B2 (en) | 1992-05-25 | 1992-05-25 | Photo detector |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| JPH05322651A true JPH05322651A (en) | 1993-12-07 |
| JP3005970B2 JP3005970B2 (en) | 2000-02-07 |
Family
ID=15077618
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP4132281A Expired - Fee Related JP3005970B2 (en) | 1992-05-25 | 1992-05-25 | Photo detector |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JP3005970B2 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112924745A (en) * | 2021-01-21 | 2021-06-08 | 季华实验室 | Nanopore gene sequencing micro-current detection device |
Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60143728A (en) * | 1983-12-29 | 1985-07-30 | Matsushita Electric Ind Co Ltd | Light receiving circuit of optical sensor |
| JPH0221920U (en) * | 1988-07-27 | 1990-02-14 |
-
1992
- 1992-05-25 JP JP4132281A patent/JP3005970B2/en not_active Expired - Fee Related
Patent Citations (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS60143728A (en) * | 1983-12-29 | 1985-07-30 | Matsushita Electric Ind Co Ltd | Light receiving circuit of optical sensor |
| JPH0221920U (en) * | 1988-07-27 | 1990-02-14 |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112924745A (en) * | 2021-01-21 | 2021-06-08 | 季华实验室 | Nanopore gene sequencing micro-current detection device |
Also Published As
| Publication number | Publication date |
|---|---|
| JP3005970B2 (en) | 2000-02-07 |
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