I am using a Wheatstone bridge to measure a resistance and an instrumentation amplifier to amplify the signal. Specifically, I am using the INA121. According to the amplifier datasheet, the input voltage can be in the range of ±2.5V and ±15V. In addition, it says that

Typical performance curves, “Input Common-Mode Range vs Output Voltage” show the range of linear operation for ±15V, ±5V, and ±2.5V supplies.

Therefore, my choice would be one of those voltages. However, which one should I choose? Does a high voltage offer advantages over a low voltage (or vice-versa) in instrumentation amplifiers?

  • \$\begingroup\$ The common mode voltage has to fall within the rails of the power supply - specifically [(V+) - 1.2] to [(V-) + 2.1] typ. So higher voltage will give you more headroom. Also, your output voltage has to fall within the power supply rails - more specifically, [(V+) - 0.9] to [(V-) + 0.15]. \$\endgroup\$
    – MOSFET
    Jan 26 at 15:11

1 Answer 1


With instrumentation amplifiers, in addition to input voltage range and output voltage range you would look it for an op-amp, you also have to pay attention to the "Diamond" diagrams to ensure you have high enough supply voltages that internal nodes don't saturate.

From your datasheet link:

enter image description here

Analog Devices has an excellent "Diamond Plot Tool" which can simplify this analysis with their products, however the part design you have is owned by TI (née Burr-Brown).


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