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 the operational amplifier. 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 PCB are typically
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. For more
detailed information, refer to Circuit Board Layout Techniques, SLOA089.
- To reduce parasitic coupling, run the input
traces as far away from the supply or output traces as possible. If not
possible to keep them separate, better to cross the sensitive trace
perpendicular as opposed to in parallel with the noisy trace.
- Place the external components as close to the device as possible. Keeping RF and RG close to the inverting input minimizes parasitic capacitance, as shown in Section 7.3.2.
- 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.