For best operational performance of the device, use good PCB layout practices, including:
- Noise can propagate into analog circuitry through
the power pins of the circuit as a whole and op
amp itself, therefore use bypass capacitors to
reduce the coupled noise by providing
low-impedance power sources local to the analog
circuitry.
- Connect low-ESR, 0.1µF ceramic bypass capacitors
between each supply pin and ground, placed as
close to the device as possible. A single bypass
capacitor from V+ to ground is applicable for
single-supply applications.
- Separate grounding for analog and digital
portions of circuitry for one of the simplest and
most-effective methods of noise suppression. One
or more layers on multilayer PCBs are usually
devoted to ground planes. A ground plane helps
distribute heat and reduces EMI noise pickup. Make
sure to physically separate digital and analog
grounds paying attention to the flow of the ground
current.
- To reduce parasitic coupling, run the input
traces as far away from the supply or output
traces as possible. If these traces cannot be kept
separate, crossing the sensitive trace
perpendicular is much better as opposed to in
parallel with the noisy trace.
- Place the external components as close to the device as possible. As illustrated in Figure 7-4, keeping RF and RG close to the inverting input minimizes parasitic capacitance.
- Keep the length of input traces as short as possible. Always remember that the input traces are the most sensitive part of the circuit.
- Consider a driven, low-impedance guard ring around the critical traces. A guard ring can significantly reduce leakage currents from nearby traces that are at different potentials.
- Clean the PCB following the board assembly for
best performance.
- Any precision integrated circuit can experience
performance shifts due to moisture ingress into
the plastic package, therefore bake the PCB
assembly after any aqueous PCB cleaning process to
remove moisture introduced into the device
packaging during the cleaning process. A low
temperature, post cleaning bake at 85°C for 30
minutes is sufficient for most circumstances.