JPS6488613A - Constant current circuit - Google Patents

Constant current circuit

Info

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
Application number
JP24717287A
Other languages
Japanese (ja)
Inventor
Akinori Takahashi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
NEC Corp
Original Assignee
NEC Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by NEC Corp filed Critical NEC Corp
Priority to JP24717287A priority Critical patent/JPS6488613A/en
Publication of JPS6488613A publication Critical patent/JPS6488613A/en
Pending legal-status Critical Current

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.
JP24717287A 1987-09-29 1987-09-29 Constant current circuit Pending JPS6488613A (en)

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)

* Cited by examiner, † Cited by third party
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

Cited By (1)

* Cited by examiner, † Cited by third party
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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