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CCS question mA

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Is the ECC81 mu-follower, attached schematic used & DN2540 schematic used without the VR tube see left up corner.
 

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Merlin,
I would take your current "sense" resistor value, multiply it by 2.25. Using that calculated number for resistor value, I would then parallel a fixed resistance and trim pot of same value to allow you to adjust it precisely to the 2,00 mA you desire. I used 2.25 to give some leeway +/- on the adjustment. You can then measure the combined resistor value and replace with a fixed or leave it as it is to allow you to adjust as required.
 
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2k resistor and 5k trimmer would work better.
Did you read the thread regarding the use of a DN2540 for <10mA? There might be some better circuits for such low currents.

It doesn't matter if it's not constant as long as it's large- see DF96's analysis. Unfortunately, the DN2540's impedance is pretty mediocre at low currents. For the 2mA you're seeking, a bipolar cascode will perform much better.

that is from the CCS fixed bias thread.
 
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