Definition

Ferrite beads suppress high-frequency noise on PCB power rails and I/O lines. Unlike inductors that store energy, ferrite beads dissipate noise as heat. On PCB power distribution, place ferrite beads after bulk capacitors and before the load to isolate noisy digital circuits from sensitive analog sections. Specify by impedance at 100 MHz (common ratings: 30Ω, 120Ω, 600Ω) and DC current rating. Package size (0402, 0603, 0805) affects current capacity and self-resonant frequency. For designs requiring EMI compliance, ferrite beads on I/O lines near connectors are often necessary to meet radiated emission limits.