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CCS question mA

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


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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.
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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