The OPAx189 series of op amps can be used with single or dual supplies from an operating range of V_S = 4.5 V (±2.25 V) up to V_S = 36 V (±18 V). These devices do not require symmetrical supplies; they only require a minimum supply voltage of 4.5 V (±2.25 V). For V_S less than ±2.5 V, the
common-mode input range does not include midsupply. Supply voltages higher than 40 V can permanently damage the device; see the Absolute Maximum Ratings table for details. Key parameters are given over the specified temperature range, T_A = –40°C to +125°C, in the Electrical Characteristics table. Key parameters that vary over the supply voltage, temperature range, or frequency are shown in the Typical Characteristics section.

The OPAx189 is unity-gain stable and free from unexpected output phase reversal. This device uses a proprietary, periodic autocalibration technique to provide low input offset voltage and very low input offset voltage drift over time 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 ensuring 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. See the Layout Guidelines section for details and a layout example.