how can I do 1 mA current source?

[toxema]

1ma current source

how can I do 1 mA current source?
if you have circuit or schematic about it can you send me ?
I have a LM317 ,can I do 1 mA current source with it?
thanks for your helps

 

[Moss]

1 ma current source

LM 317 is not good solution because 1mA current is too small for this IC. There is many different version of current sources, some with BJT, some with OP amps...

Small addition. This attachment is three pages from "The art of electronics", where current sources are examined.

 

[mince]

current source 1ma

Not sure on your exact application, but ou could maybe use a current mirror with a resistor to set the reference current.

**broken link removed**

Page 5 gives a schematic.

 

[ambreesh]

bf245 current source

goto this links it may help
h**p://www.national.com/nationaltv/
h**p://www.elecdesign.com/Departments/DepartmentID/6/6.html

 

[IanP]

constant current source with bf245

If you need a very simple 1mA current source use a N_FET transistor (BF245, or similar) and 1k variable resistor (later you can replace it with a fixed resistor if you know after you know the exact value) and connect them in configuration as per attached drawing ..

 

[ezpcb]

bf245 typical example

If high accuracy is required, an oprational amplifier based current source is OK. choose high impendence OP chip and precision resistors for you design, you'll get excellent performance

mike


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[aslak]

current source bf245

What is your input voltage? If it is low enough, check the latest current mirror based white led drivers for example from Maxim.

http:// maxim-ic.com

Aslak

 

[tjalps]

how to get 1ma current source

Hello!

If you need acurate current source you could use several Texas Instruments (w*w.ti.com) current references REF200AU.

Regards!