LT6375 offset voltage issue

Hi,

I am using LT6375 as a unity gain amplifier for current sensing application. For current sensing 0.025 ohm series resistor is used. LTC6371 is giving output voltage of 0.110V for zero input current. It is configured as highlighted in below image.

I tried another configuration to reduce the offset voltage, with below highlighted configuration i am getting 0.063V output voltage for zero input current. As per datasheet output voltage should be maximum 0.450 mV. Please do suggest ways to reduce the offset voltage. Any suggestion will be appreciated.

   

Please do let me know in case you want more info.

    •  Analog Employees 
    on Oct 26, 2020 7:46 PM 1 month ago

    Difference amplifiers will have two sources of error-- the Vos and the CMRR. The Vos is specified with a minimal common-mode component so CMRR can be neglected. In a current-sense application, there will generally be a significant common-mode applied and the CMRR will [vastly] dominate, leading to higher than expected errors as noted. This is the reason that there are specialized ICs designed to perform current-sensing, namely using topologies that are relatively immune to applied common-mode. A typical current sense circuit will have gain set high enough that the Vos will not be amplified needlessly large, but enough to provide scaling appropriate for the max current to be measured, so typical values range from 20-50. For best precision, a 'zero-drift' or 'chopper-stabilized'  input structure is desirable (for example, LTC6102).