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Can AD5933 use voltage input instead of current input?

Question asked by Alex_I on Dec 1, 2014
Latest reply on Aug 31, 2015 by musach

Hello,  I am trying to interface AD5933 to a device under test in a somewhat unusual way.  The device has four ports, the inputs take current and the outputs are voltages.  This is still an impedance measurement, only backwards from what AD5933 expects...  I first thought to convert the AD5933 output voltage to current, and then convert the device output voltage to current as AD5933 expects (Option A in the diagram below), but two conversions may not result in excellent accuracy.  I am wondering, is it possible to just feed AD5933 a voltage?

 

From the block diagram in the datasheet, it looks like it should be possible to connect a voltage source to the RFB pin, and NOT connect anything between RFB and VIN, effectively bypassing the input current-to-voltage converter of the AD5933 (Option B in the diagram).  I think the RFB voltage should be relative to whatever is at VIN, presumably using a differential amplifier or level shifter.  Would this work?  Is there a better way to accomplish the same goal?

 

Thanks!

 

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