Constant Current Source Circuit

[mrfeedback]

Hello All,
This 2 terminal constant current source is shown in EW magazine circuit ideas.

The formula given is - I const = 2 (Vf - Vbe/ R), where

Vf = Led voltage drop, Vbe = vbe for Tr1 & Tr2, R = R1 = R2.

Simulation shows
10v - 8.810 mA
20v - 8.833 mA
30v - 8.854 mA
40v - 8.873 mA
50v - 8.891 ma

Maybe this is old hat to some of us, maybe useful to others of us.
Is this good performance ?.

Regards, Eric.

 

[mrfeedback]

Doh !

I forgot to add this -

The 2 terminal circuit shown here is composed of a pair of complimentary constant current sources, where each provides a constant current for the voltage reference of the other, thereby improving performance. Compliance is excellent and the current can be set to almost any value. Power dissipation and voltage withstand are limited only by the transistors chosen. The circuit can be made up on a tiny piece of stripboard, and makes an excellent replacement for current setting resistors in many audio power amplifiers.

David N J White
Bearsden
Glasgow
G3

Regards, Eric.

 

[GRollins]

The image doesn't show up.

Grey

 

[mrfeedback]

repost image ?

This is posted as bitmap - maybe it works for you.

Regards, Eric.

 

[paulb]

Um, still missing the image.

 

[GRollins]

Posting the image as a file on your computer won't work. You can see it, but no one else can. You'll have to upload the image.

Grey

 

[mrfeedback]

Thanks Grey, what do I do ? to upload the image - yes I have been nominating my hard drive file address after I click the IMG button on the GUI.

Thanks.

 

[grataku]

mrfeedback,
you should ask HarryHaller, he's really got the illustration posting techniques down.

 

[tschrama]

H.H. is the king al pictures