Inductor Guide: Types, Core Materials, and Applications for Electronics Buyers

Inductor Guide: Types, Core Materials, and Applications

Inductors are often the least understood passive component. Choose wrong, and your power supply oscillates, your filter doesn't filter, or your circuit emits audible noise. We've seen all three failures traced back to an inductor picked by value alone.

Here's a practical guide to inductor types, core materials, and popular parts.

Air Core Inductors

No magnetic core material — just wire wound in free space.

Best for: High-frequency applications (100MHz+), RF circuits

Advantages: No core loss, no saturation, linear response

Disadvantages: Lowest inductance per turn (physically large for high values), strong magnetic field leakage

Common in: RF filters, antenna matching, LC oscillators

Ferrite Core Inductors

Core material: Ferrite (iron oxide + nickel/zinc/manganese compounds)

Best for: Switching power supplies, EMI filters, broadband transformers

Inductance range: 1 µH to 100 mH

Two main ferrite families:

• MnZn (manganese-zinc): Higher permeability, lower frequency (up to ~2MHz)
• NiZn (nickel-zinc): Lower permeability, high frequency (up to ~100MHz)

Popular parts:

• NR series (SMD ferrite power inductor, 1µH-100µH)
• CDRH series (shielded SMD, low radiation)
• T-core inductors (through-hole, high current)

Chinese alternatives: SUMIDA, CYNTEC, Sunlord (now the world's largest inductor manufacturer by volume)

Iron Core / Iron Powder Inductors

Core material: Carbonyl iron or iron powder mixed with binder

Best for: High-current switching power supplies, buck converters

Advantages: High saturation current, handles DC bias well

Disadvantages: Higher core loss, larger size vs ferrite for same inductance

Common part series: T-core (through-hole toroid), MS series (potted SMD)

Shielded vs Unshielded

Shielded versus unshielded is the first question we ask on any power layout, before we even look at inductance.

Choose shielded when:

• Components are within 5mm of the inductor
• You're passing FCC/CE emissions testing
• Audio circuits (prevents magnetic hum coupling)

Choose unshielded when:

• Cost is the priority
• Board layout isolates the inductor
• Very high inductance values are needed

Selecting an Inductor (Step-by-Step)

1. Determine required inductance (L) — From your circuit design or reference design
2. Calculate peak current — The maximum current the inductor will see, including ripple
3. Check saturation current (Isat) — Must exceed peak current by at least 20%
4. Check rated current (Irms) — Must exceed average current plus margin
5. Verify DC resistance (DCR) — Lower = less resistive loss, but larger and more expensive
6. Choose type — Shielded or unshielded based on layout

Common Inductor Applications

References

• TI Power Management Guides
• IEEE Power Electronics