Signal & Power Integrity
The physics that decides whether a board works once signals get fast or currents get large. These topics are cross-cutting — they apply to every circuit block, not just one. Learn them once and apply everywhere.
The concepts​
| Topic | The core idea | Page |
|---|---|---|
| Signal integrity (SI) | Fast edges = transmission lines; reflections, terminations, crosstalk | Signal Integrity |
| Return paths & grounding | Current always returns; keep its path under the signal | Return Paths & Grounding |
| EMI / EMC | Emissions & immunity; pass compliance and don't self-interfere | EMI / EMC |
| Impedance & stackup | Trace geometry + layer stack set the impedance | Impedance & Stackup |
| Copper pours & thermal | Fill zones, thermal relief, plane capacitance, heat | Copper Pours & Thermal |
Why it matters​
A schematic can be perfect and the board still fail because of how it's laid out: a trace that reflects, a return current forced to detour, a plane split that radiates. These five topics are the difference between "the simulation passed" and "the hardware passes EMC and boots every time."
They're connected
SI, return paths, EMI and impedance are the same physics seen from different angles. A clean return path is good SI and low EMI and controlled impedance. Fix the ground/stackup and most problems shrink at once.