Which PCB layout practice helps minimize noise and EMI?

• A. Keep analog and digital sections mixed to save board space
• B. Route high-current traces near sensitive nodes
• C. Use ground planes
• D. Place decoupling capacitors far from pins

Answer: (C)

Using a continuous ground plane minimizes noise and EMI by giving signals a low-impedance, close return path and by shrinking the current loop that a signal creates. The return currents flow under the signal traces, so a solid plane keeps loop areas small and reduces radiated emissions and susceptibility to external noise. It also provides shielding and a stable reference for both analog and digital sections, helping keep voltages well-behaved and reducing crosstalk. For best results, keep the plane uninterrupted and well tied to system ground, and place decoupling capacitors close to power pins to supply fast current bursts. Practices like mixing analog and digital regions, routing high-current traces near sensitive nodes, or placing decoupling capacitors far from pins undermine these benefits.