9 Power Supply Recommendations

The OPAx397 are specified for operation from 1.7 V to 5.5 V (±0.85 V to ±2.75 V).

CAUTION

Exceeding supply voltages listed in the Absolute Maximum Ratings table can permanently damage

the device.

10 Layout

10.1 Layout Guidelines

Pay attention to good layout practice. Keep traces short, and when possible, use a printed-circuit board

(PCB) ground plane with surface-mount components placed as close to the device pins as possible. Place

a 0.1-µF capacitor closely across the supply pins. These guidelines must be applied throughout the analog

circuit to improve performance and provide benefits such as reducing the electromagnetic interference (EMI)

susceptibility.

For lowest offset voltage and precision performance, circuit layout and mechanical conditions must be optimized.

Avoid temperature gradients that create thermoelectric (Seebeck) effects in the thermocouple junctions formed

from connecting dissimilar conductors. These thermally-generated potentials can be made to cancel by making

sure these potentials are equal on both input terminals. Other layout and design considerations include:

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

• Use guard traces to minimize leakage current when ultra-low bias current is required.

• Thermally isolate components from power supplies or other heat sources.

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

Following these guidelines reduces the likelihood of junctions being at different temperatures, which can cause

thermoelectric voltage drift of 0.1 µV/°C or higher, depending on materials used.

10.2 Layout Example

+

V

IN

V

OUT

R

G

R

F

Figure 10-1. OPA397 Layout Schematic

Minimize

parasitic

inductance by

placing bypass

capacitor close

to V+.

Route trace under package for output to

feedback resistor connection.

V+

±IN

+IN

V±

OUT

Keep high

impedance

input signal

away from

noisy traces.

Figure 10-2. OPA397 Layout Example

OPA397

SBOSA02 – AUGUST 2021

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