7.3 Feature Description

The OPAx187 is unity-gain stable and free from unexpected output phase reversal. This device uses a proprietary, periodic autocalibration technique to provide ultra-low input offset voltage and near zero input offset voltage drift over temp and temperature. For lowest offset voltage and precision performance, optimize circuit layout and mechanical conditions. Avoid temperature gradients that create thermoelectric (Seebeck) effects in the thermocouple junctions formed from connecting dissimilar conductors. Cancel these thermally-generated potentials by making sure they are equal on both input pins. Other layout and design considerations include:

Use low thermoelectric-coefficient conditions (avoid dissimilar metals).

Thermally isolate components from power supplies or other heat sources.

Shield operational amplifier and input circuitry from air currents, such as cooling fans.

Follow these guidelines to reduce the likelihood of junctions being at different temperatures, which may cause thermoelectric voltages of 0.1 µV/°C or higher, depending on the materials used.