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OPA211-HT: Non linearity at input voltage less than 1.25V

Part Number: OPA211-HT

Hello,

I am using "OPA211-HT" (since it is available in KGD form). With unity gain for input voltage from 0 to 3.3V, I get linear output. But when I set gain to 4.16, I see non liner behavior for input voltage below 1.25V.  If it is due to common mode voltage limitation, why do we have it only with higher gain?.

Thanks,

Nischitha

  • HI Nischitha,

    Yes, it is due to both the input common-mode voltage limitation as well as an output swing limitation.

    The OPA211-HT input common-mode requires at least +2 V above the negative supply and 1.4V below the positive supply.

     

    The output swing is also limited to about 200mV from the supply rails, hence the device will not be able to produce output voltages close to GND while powered with an unipolar +15V  and ground supply.  

    Therefore, the OPA211-HT circuit requires a negative voltage supply to produce linear results amplifying the in the circuit above. The circuit will require a negative supply of -2V (or more negative) to meet the input common-mode range specification.

    Thank you and Regards,

    Luis