JPS6488613A - Constant current circuit - Google Patents
Constant current circuitInfo
- Publication number
- JPS6488613A JPS6488613A JP24717287A JP24717287A JPS6488613A JP S6488613 A JPS6488613 A JP S6488613A JP 24717287 A JP24717287 A JP 24717287A JP 24717287 A JP24717287 A JP 24717287A JP S6488613 A JPS6488613 A JP S6488613A
- Authority
- JP
- Japan
- Prior art keywords
- transistor
- current
- constant current
- photodiode
- variable
- 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
Abstract
PURPOSE:To make a current variable from an extremely small value to a large value by providing a variable voltage source which is connected to the base of a second transistor whose emitter is connected to the output terminal of an operational amplifier and which is paired with a first transistor. CONSTITUTION:A photoelectric current compressing circuit is constituted of a photodiode PD, an operational amplifier A, and the transistor Q1 whose collector and base are connected with each other in order that a photoelectric current in pA order can be easily obtained. The transistor Q2 and the variable voltage source VK have a function to logarithmically extend an output voltage from the amplifier A; a necessary constant current is obtained from the collector of the transistor Q2. To obtain a photoelectric current from the photodiode PD, an LED drive voltage V1 and a resistor R1 are prepared to control a light output from a light-emitting diode LED. In such a way, without using costly resistors from a large value to a small value,a constant current circuit whose temperature characteristic is excellent over a wide range of variation of current from a few pA to a few tens of mA can be obtained.
Priority Applications (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP24717287A JPS6488613A (en) | 1987-09-29 | 1987-09-29 | Constant current circuit |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
JP24717287A JPS6488613A (en) | 1987-09-29 | 1987-09-29 | Constant current circuit |
Publications (1)
Publication Number | Publication Date |
---|---|
JPS6488613A true JPS6488613A (en) | 1989-04-03 |
Family
ID=17159511
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
JP24717287A Pending JPS6488613A (en) | 1987-09-29 | 1987-09-29 | Constant current circuit |
Country Status (1)
Country | Link |
---|---|
JP (1) | JPS6488613A (en) |
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH02309706A (en) * | 1989-05-24 | 1990-12-25 | Nec Corp | Voltage/current converting circuit with output switching function |
-
1987
- 1987-09-29 JP JP24717287A patent/JPS6488613A/en active Pending
Cited By (1)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
JPH02309706A (en) * | 1989-05-24 | 1990-12-25 | Nec Corp | Voltage/current converting circuit with output switching function |
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