This thread has been locked.

If you have a related question, please click the "Ask a related question" button in the top right corner. The newly created question will be automatically linked to this question.

INA826: INA826: guidance regarding interfacing to sensor

Part Number: INA826

Hello,

I am currently using the INA826 amp in a product.  I need to upgrade the design now and would really appreciate any input regarding my upgrade effort.  Currently I have an analog channel in a product that interface to differential sensors and this is the first amp they connect to.  Here is a rough sketch of the direction I'm looking to go in:

Currently the inputs to the INA826 are capcitively coupled.  I now need to be able to read sensor signals from DC.  The amp is powered with 3.3V as Vcc and it is in a single supply configuration.  I need the amp to output 1.65V at steady state (zeroed out) and when the sensor is excited it will give me an oscillation similar to the output wave form I drew.  All in all this isn't super complex, but I'd like to get some input from those more familiar with analog design than myself.  So a couple question:

1. Is it normal to use a DAC to drive the Vref pin allowing me to overcome any input mismatches between the IN+ and IN- pins?  Say if my sensor plus and minus signals are mismatched by 10-20%

2. I'm using a processor from TI and would like to stick with TI parts, does TI have a DAC that lends itself to this type of DAC that is tailored to this or should I just be looking for a general with the right resolution and digital interface?

3. Should there by any kind of basic passive input filter on the IN+ and IN- signals or is it best to just bring them into the amp?  The next state will be a multipole low pass filter so the overall design will filter this signal before it gets to the ADC.

4.  I'm assuming R1 and R2 should be as large as I can make them (as long as they satisfy the INA826 data sheet for any required pull-downs on the inputs) so they don't interfere with any attached sensor bridges?

(as a note the sensor bridge resistors are on the order of 1k or less and the gain for this amp will be 1)

Any input is welcome.  I'm just trying to get an idea of how to properly design this first initial interface.

Thanks,

Rob