emontllo
Full Member level 4
Hello,
I am designing a current sense circuit based on a Kelvin current sense resistor and an amplifier. View attachment current sense preamp.pdf
The preamplifier (Gain 30.3) is a differential amplifier based on a precission opamp (OPA4727 https://www.ti.com/lit/ds/symlink/opa4727.pdf ).The datasheet says that the maximum input offset voltage is 175 uV. However, output offset voltage at zero current is 25 mV wich means that input offset voltage is (a lot!) higher than the specifications.
As can be seen all resistors are 0.1%, operation temperature was 26 ºC.
Is it normal to have such a high offset? Which is the reason? Some ideas...
- Input offset is specified only at 10 V supply only?
- Common mode voltage affects offset?
- Input bias current...
Thank you for your comments and answers!
Ernest
I am designing a current sense circuit based on a Kelvin current sense resistor and an amplifier. View attachment current sense preamp.pdf
The preamplifier (Gain 30.3) is a differential amplifier based on a precission opamp (OPA4727 https://www.ti.com/lit/ds/symlink/opa4727.pdf ).The datasheet says that the maximum input offset voltage is 175 uV. However, output offset voltage at zero current is 25 mV wich means that input offset voltage is (a lot!) higher than the specifications.
As can be seen all resistors are 0.1%, operation temperature was 26 ºC.
Is it normal to have such a high offset? Which is the reason? Some ideas...
- Input offset is specified only at 10 V supply only?
- Common mode voltage affects offset?
- Input bias current...
Thank you for your comments and answers!
Ernest