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.

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

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