• State Resolved
  • Locked Locked
  • Replies 1 reply
  • Subscribers 49 subscribers
  • Views 857 views
  • Users 0 members are here
Support feedback
Options
Options
Similar topics

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.

INA129 and ADS 1278 noise issue?

Qi Tang
Intellectual 370 points
Other Parts Discussed in Thread: OPA211, INA129, INA103, INA163
Hi,
I using HT version of INA129 and ADS1278 to measure slow signals of +/-2.5V range(scaled down). 
Becasue ADC input range is 0 to 5V, I put +2.5V reference (from REF5025) for both and no gain
resistor used(G=1).
I put 2 differential inputs of INA129 together and sample 1024 points every half second. What
I found is the difference between samples are around 2000 counts;
In the same board, I used OPA211 as voltage follower instead of INA129. I put fixed 2.5V and
do the same thing as above. What I got the difference between 
samples are around 100 counts, much smaller.
Why and what is the solution as I need differetial inputs?
Thanks for your kind help!
  • 0
    TI__Mastermind 25775 points

    Hello Qi,

    Comparing the input voltage noise density curves in the INA129 and OPA211 datasheets we see that the INA129 has ~117 times as much noise at 1Hz, hence much greater variation in the output as seen by the 24-bit converter.

    If you are looking for a low-noise instrumentation amplifier with good bandwidth I suggest looking at the INA103 and INA163.