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AD8400 Digital Potentiometer Voltage Range

Question asked by cgervasi on Jul 8, 2011
Latest reply on Jul 14, 2011 by musach

I'm using an AD8400 potentiometer in the feedback path of an op-amp powered with +/-12V supplies.  The DC bias is 2.5V.  The circuit is oscillating.  I think the problem is a transient negative voltage on the op-amp output forward biases the protection diodes and causes excessive current flow into the VCC pin.  This pulls down my resistor divider 5V supply.  If the pot kept working during the transient, the negative voltage from the output would make its way to the inverting node of the op-amp and pull the output back to 2.5V.

 

DigitalPotFB.jpg

 

What is the best approach?

  1. Use a 5V supply to the AD8400 that's capable of handling more current.
  2. Use a pot that supports higher voltage and/or reduce the rails on the op-amp so they're equal to the rails of the pot?

 

Is there ever a way I can use this part in a circuit that has transients beyond the pot's supplies?

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