OPA388_17 Datasheet, PDF (23/34 Pages) Texas Instruments – Precision, Zero-Drift, Zero-Crossover, True Rail-to-Rail Input/Output, Operational Amplifiers

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10 Layout
OPA388, OPA2388, OPA4388
SBOS777 – DECEMBER 2016
10.1 Layout Guidelines
Paying attention to good layout practice is always recommended. 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 assuring
they are equal on both input terminals. 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.
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
Run the input traces
as far away from
the supply lines
as possible
Place components
close to device and to
each other to reduce
parasitic errors
RG
GND
RF
N/C
±IN
VS+
N/C
V+
GND
VIN
+IN
V±
OUTPUT
N/C
Use low-ESR, ceramic
bypass capacitor
Use low-ESR,
ceramic bypass
capacitor
GND
VS±
VOUT
Figure 47. OPA388 Layout Example
Ground (GND) plane on another layer
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