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, as well as 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, 0.1-μF ceramic bypass capacitors
between each supply pin and ground, placed as close to the device as possible. A
single bypass capacitor from VCC+ to ground is applicable for single-supply
- 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 EMI noise pickup. Take care 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 it is not possible to keep them separate, it is much 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 11.2.
- 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.