AD8421 output offset of -400mV

both the inputs are shorted but even then at the o/p  i m getting -400mv

+/- 12V supply is clean

plz c the attached schematics..

just for debugging this issue all other components are removed from the board and the input is shorted.

  • Hi Aditya,

    You might have a floating inputs and you can resolve this by connecting the shorted inputs to ground. Make sure that all the reference ground on your setup are connected. Let me know if this solves your problem.

    You may also want to explore this very helpful tool: Instrumentation Amplifier Tool - Common Mode vs. Output Voltage (Diamond Plot) which could verify if your setup is within the operating range of the specific instrumentation amplifier.

    Best regards,


  • hi emman

    thanks for your inputs

    when i replaced with the another new component it works fine....

    now the output from this ina is connected to AD8067 then i am getting oscillations of freq 50Mhz (pk-pk 4.2V at the offset of 9V) at the output of this opamp.

    plz c the attached schematics

    i have removed C659 & R463

    thanks & regards,


  • hi harry

    thanks for your reply

    i also noted this but as per datasheet if we shunt inputs with 50 ohm resistor then we should be able to work with gain less than 8..

    can u please recommend me the best opamp for the following filter need:

    (0-10khz signal) --> (INA-AD8421) --> anti-aliasing LPF (3db BW or passband of 10Khz and  -90db attenuation at 2.5Mhz)  --> (Sigma Delta ADC - ADS1271)

    as of now i used the filter design tool and as per that only i got AD8067 because of least noise

    i need to design a filter such that its noise is minimal to achieve 17bits of accuracy

    thanks again and warm regards,


  • plz c the image below for clarification regarding operation of ad8067 at gain less than 8

    my signal is peak to peak 10 V hence i need a opamp who works at more than +/- 5 V

    whether rail to rail opamps will be safe?