OPA192: How to determine gain setting resistor's valus?

Charles Zhang1

Part Number: OPA192

Hi Team,

My customer is using OPA192 for high side current sensing like below, about the gain setting resistors, how to determine the appropriate value?

What should be taken into account if we choose small resistors?

Regards,

over 3 years ago

+1 kai klaas69 over 3 years ago

Guru 140200 points

Hi Charles,

the major issue here is the common mode rejection. With discrete resistors the common mode rejection will be about 40dB with 1%-toleranced resistors and 60dB with 0.1%-toleranced resistors. I would heavily recommend to use a specialized TI's current sense amplifier. They offer a common mode rejection of up to 140dB, because these resistors are processed on the same die and are nearly identical:

https://www.ti.com/amplifier-circuit/current-sense/analog-output/products.html

Kai

+1 Thomas Kuehl over 3 years ago

TI__Guru* 93105 points

Hi Charles,

If for some reason you don't want or can't go with a current shunt monitor IC having inclusive resistors as Kai's recommends we can revisit using a precision op amp and external resistors.

Regards, Thomas

Precision Amplifiers Applications Engineering

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OPA192: How to determine gain setting resistor's valus?