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ADS1299: How to interpret the Gain error?

Monti Om
Prodigy 30 points
Part Number: ADS1299


Hi

We work mostly on the research side of EEG and are not really trained in Electrical Engineering.

How to interpret the gain error value given on page 9 of ADS1299 datasheet? It is given as 0.1% of FS (typical). 

Does it affect amplitudes and if so how to find value in microvolts? Does gain error affect phase or frequency? 

  • 0
    TI__Mastermind 19815 points

    Hi,

    Let me discuss with other engineer and get back to you around 6/29/

    Thanks

  • +1 in reply to ChienChun Yang
    TI__Mastermind 19815 points

    Hi,

    Gain error is one of the common ADC error or deviation that you could do some study online. The other common ADC error or deviation is called offset error.

    -------

    For quick and layman's terms, gain error is the error or deviation due to the slope of ADC's transfer function is not perfectly equal to 1, this leads that the difference(i.e. the deviation or error) between the true reading and the converted ADC code may not be always the same when input signal from small to large value.

    E.g. let x1<x2. When at small input signal, x1, the ADC code quantizes to y1. When at high input signal, x2, the ADC code quantizes to y2.

    Ideally, if no gain error and no offset error, (y1-x1)=(y2-x2)=0, but such IDEAL ADC doesn't exist.

    So, in reality non-ideal ADC, (y1-x1) is not the same as (y2-x2), so (y1-x1)~=(y2-x2)~=0. This is the gain error.

    --------------------------------------------

    so 0.1%FS means that the error difference between the ADC code and true reading could be - if the FS Voltage is 4.5V, then the error or deviation could be 0.1% i.e. 0.001 * 4.5V = 4.5mV, i.e. ADC code may read 4.5V-0.0045V = 4.4955V when the input signal is at around 4.5V.

    ----------------------

    Can you explain a bit more about what you mean by

    "Does it affect amplitudes and if so how to find value in microvolts?

    Does gain error affect phase or frequency? "

    Thanks