INA351: What's the main spec and application differences between INA351 with INA181?

Hi Francis,

Both devices share the INA part name, but offer different functions.

INA351 is a general purpose three op amp INA with digital gain select and a buffered reference driver internal to the device. This device is great for interfacing with bridge sensors or similar applications where we are trying to reject common mode signals and amplify differential mode signals. The INA351 has great matching characteristics, allowing the device to have a very competitive gain error of 0.015% typical gain error. 

Here is the architecture of the INA351:

Alternatively, the INA181 is a bi-directional current sense amplifier. This architecture effectively looks like a difference amplifier in design:

Uniquely, the INA181 can tolerate common mode voltages in excess of the supply rail of the device. 

I would expect the INA181 to be implemented into applications involving current sensing, whereas the INA351 fits best into applications requiring amplifying small differential voltages from high impedance sensors, or amplifying small differential voltages coupled onto relatively large common mode signals.

From an impedance perspective, inputs looking into the INA351 see very high input impedance since we drive the non-inverting inputs of CMOS amplifiers. The INA181 has input signals which see the impedance of the resistive network, however this error is typically negligible as the sense resistor value will be very small in resistance. 

What is the goal for your application? We are happy to help suggest devices which are best fit for your design goals.

Thanks,

Jacob