high current digital potentiometer?


I am a Electrical Engineering student working on a senior design project. One of the features of project is to control the bias current going into the power tubes of a vacuum tube amplifier. Our range of control needs to go from 30 mA to about 137 mA. The voltage across the digi pot should be around 5.5V. Do you know of any digital pots capable of handling this kind of current? A 100k resistor would work but a 1Meg resistor would be a dream come true.

If you don't know of any digipots capable of handling that do you have any other ideas as to how to digitally control the bias current with an Arduino Zero?



  • Hello wca62,

    Interesting problem to solve. From my personal investigations of digital pots a few years ago there was nothing that would handle much current. I will transfer this question over to the precision DACs space on the forum since they support the digital pots offerings.  https://ez.analog.com/community/data_converters/precision_dacs 

    But, I think your only solution will be to use a digital pot and an amplifier of some sort. Either a BJT or an opamp to amplify the output of a digital pot. You also have to think about what happens if there is a circuit fault. I recently had an issue where a CMOS switch failed putting 18V out onto the logic input pin that was coming from a controller running on 5V. It did not like 18V on its output pin. So a little isolation of an amp stage may be a good thing.  

    Dave T