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AD5248 lowest resistance

Question asked by mkrolick on Feb 27, 2011
Latest reply on Mar 3, 2011 by AndyR
I am trying to implement a volume control using a standard noninverting amplifier configuration (http://upload.wikimedia.org/wikipedia/commons/4/41/Op-Amp_Inverting_Amplifier.svg) where the feedback resistor is a AD5248 digipot (using terminals B1 and W1 of the AD5248 as a rheostat)and Rin is a 2.5k fixed resistor. When I reduce the gain to zero by setting the resistance to the lowest possible setting, there still exists an output signal on the amplifier because the datasheet for the AD5248 explains that there is a contact resistance on the wiper of around 50 ohms. The datasheet also explains that there is a "shutdown" bit that will bring the resistance between the wiper and terminal B down to "almost 0 ohms" but doesn't mention what the actual resistance is.
Can you tell me what the actual resistance is in this mode because it seems to have no effect on the signal as if the resistance was normally set to the lowest value.
Also, can you recommend a digipot that has a very low resistance on the lowest resistance setting (very close to 0ohms)?
Thank you.

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