AnsweredAssumed Answered

AD7606 Analog Input Ground Pins

Question asked by kidsnave on Dec 11, 2013
Latest reply on Dec 12, 2013 by jcolao

The AD7606 shows what appear to be differential amplifiers at each of the analog inputs.  There is no mention of a common-mode voltage limit between VxIN and VxGND for any of the inputs.

 

My application has four inputs with a +2.5V offset and four other inputs with -2.5V offset.  The positive offset signals only go more positive (+2.5V to +7.1V) and the negative signals only go more negative (-2.5V to -7.1V).  I have to use the 10V range but only get about 5V of useful information.

 

Can I use my +2.5V bias on the VxGND pins for the positive inputs and the -2.5V bias for the negative inputs to cancel the offset?

 

This would give me a 5V range and double my effective resolution.  I could accomplish the same thing with eight op-amps on the inputs to subtract out the bias, but this is expensive, uses more real estate and may introduce more noise and linearity errors, negating the improved resolution.ckt_sketch.bmp

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