Definition

AC coupling uses series capacitors to pass AC signal components while blocking DC voltage between circuits. It's essential when driver and receiver have different DC bias levels. For PCB layout, place coupling capacitors close to receivers to minimize stub length. On differential pairs, use matched capacitor values (±5% or better) to avoid introducing skew between P and N lines. High-speed serial links (PCIe, USB, Ethernet) typically require 100nF AC coupling caps in 0402 or smaller packages. Check your protocol specification for capacitor requirements and placement guidelines.