For best operational performance of the device, use good printed circuit board (PCB) layout practices, including:
- Noise can propagate into analog circuitry through
the power pins of the circuit as a whole, as well
as through the op amp. Bypass capacitors are used
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 is 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 electromagnetic interference (EMI) noise pickup. Take care to physically separate digital and analog grounds, paying attention to the flow of the ground current. For more detailed information, see Circuit Board Layout Techniques.
- 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 7-3, keeping RF and RG close
to the inverting input minimizes parasitic
capacitance on the inverting input.
- 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.
- Cleaning the PCB following board assembly is recommended for best performance.
- Any precision integrated circuit can experience performance shifts resulting from moisture ingress into the plastic package. Following any aqueous PCB cleaning process, baking the PCB assembly is recommended 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.