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With a three-terminal analog pot, you can use the middle and one of the outer terminals for it to function as a rheostat.

As it happens, I need a digital rheostat in my circuit but I only have digipots on hand: an MCP4151 and an MAX5481. Since this is a one-off project and I'd rather not wait for a digital rheostat to be delivered, I'm wondering if it's possible to use a digipot as a digital rheostat, perhaps with some extra circuitry if needed?

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  • \$\begingroup\$ Anthony, how much power are you planning to dissipate in your digital rheostat? Remember, power varies as the square of current. As the load resistance gets lower, the current rises and so does the dissipated power. "Analog" rheostats often suffer most at the lower end of their adjustment range (i.e. lowest resistance) because of this effect. Depends on how the rheostat is connected in the circuit. Calculations required to ensure smoke-free operation. \$\endgroup\$ – FiddyOhm Jun 15 '18 at 22:19
  • \$\begingroup\$ Thanks for your comment, I wasn't aware of that. This circuit is for a wah guitar pedal, and the rheostat is in the signal chain, so I think it should be OK. At least, I've already tried the accepted answer and it worked without any smoke or other issues. Thanks again. \$\endgroup\$ – Anthony Jun 15 '18 at 23:17
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The MAX5483 and MAX5484 appear to be, the MAX5481 does not appear to be:

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Source: MAX5481 datasheet

It appears the MCP4151 can be used as a rheostat:

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Source: MCP4131 Datahsheet

Note 1 reads as follows:

Floating either terminal (A or B) allows the device to be used as a Rheostat (variable resistor).

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  • \$\begingroup\$ Thank you very much! I missed the note on the MCP datasheet. \$\endgroup\$ – Anthony Jun 15 '18 at 21:19

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