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Circuit for LED switching control. LED supplied by the precision current source

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stneinfrst

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I want to make the switch for LEDs control, which are controlled by Arduino.
I have a current source with precision value of current. This value must be unchangeable.
And I think that the typical circuit for switching (which presented on image) isn't suit for it, because
transistor can exert influence on current value, isn't it?
What kind of circuit allows to control precision values of current? Without any influence on current value.
trasnistor.JPG
 

stneinfrst said:
I have a current source with precision value of current.
Click to expand...

The definition of a current source is that it delivers an unchanging Ampere level, regardless of what component is in the path.

I guess you are talking about the bias current? The B-E junction is a PN junction which drops 0.6V. Therefore the current source will increase or decrease its voltage, to overcome the diode drop.

You must be careful not to exceed the transistor's safe rating for B-E current. This might be just a few mA.
 

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