Inductors 101
Inductors are the quiet workhorse of power circuits — resisting changes in current, storing energy in a magnetic field, and filtering noise. Here's what to look for when picking one.
What an Inductor Does
An inductor resists changes in current flow, storing energy in a magnetic field when current increases and releasing it when current drops. That makes it essential in switching power supplies, filters, and anywhere you need to smooth out current spikes.
Specs That Matter
- Inductance (µH or mH) — how strongly it resists current changes
- Rated current — the maximum current before the core saturates and inductance drops off
- DC resistance (DCR) — series resistance of the winding; lower is more efficient
- Self-resonant frequency — the point where the inductor stops behaving like one
Common Types
- Toroidal — wound on a ring core, low EMI radiation, common in power supplies
- Wirewound (radial/axial) — simple, general purpose
- SMD power inductors — compact, used on space-constrained boards like DC-DC converters
Choosing the Right One
Match the inductance value to your circuit's design (often specified by a regulator IC's datasheet), then size the current rating with headroom above your circuit's peak current — running an inductor near its saturation current causes it to lose inductance exactly when you need it most.