Chip Inductor
A chip inductor is a tiny multilayer or wirewound surface-mount inductor (typically 0402–1210) used for impedance matching, RF filtering, and small DC–DC stages where space dominates the budget.
Multilayer parts are stacked ferrite-and-conductor layers fired into a monolithic chip; wirewound parts have a fine spiral around a tiny ceramic or ferrite core. Inductance comes from the loop geometry; Q and self-resonant frequency depend on the conductor cross-section and the dielectric losses of the substrate.
In plain terms
Imagine a flywheel spinning in line with the current. Once it's up to speed it wants to keep going; ask it to suddenly stop and it pushes back hard.
Why designers use it
- Match an antenna to a 50 Ω feedline with a high-Q wirewound chip.
- Filter VCO/PLL supplies on RF transceivers without taking board space.
- Set the frequency response of small low-power LC filters in compact wearables.
Best for
- RF impedance matching
- Pi/T filters
- Compact low-current DC–DC
Key specifications
- Inductance: 1 nH – 100 µH
- Q factor: 5 – 80 (Higher = lower loss)
- Self-resonant: 100 MHz – 30 GHz
- DCR: 0.05 Ω – 5 Ω
- Tolerance: ±2 % – ±20 %
When not to use it
- When >500 mA of DC current is needed — chip inductors saturate or burn the trace.
- Above the part's self-resonant frequency — it stops behaving as an inductor and looks capacitive.
- When DCR matters and a wirewound power inductor in 3 × 3 mm would actually fit.
Common mistakes
- Picking a multilayer part for an RF match where a wirewound's higher Q would have given 1 dB more gain.
- Forgetting the SRF spec and using a 100 nH part above 1 GHz where it has gone capacitive.
- Underestimating the tolerance — chip inductors are often ±10 % and that walks the tuned frequency.
Where you will find it
- A Bluetooth module's antenna matching network uses a 2.2 nH chip inductor in an L-match circuit to transform the PCB's 50 Ω trace impedance to the antenna's impedance, maximising radiated power and achieving the stated +4 dBm output.
- A smartphone's NFC circuit uses a series chip inductor with the antenna coil to tune it to exactly 13.56 MHz: off-resonance by even a few percent and the inductive link to a payment terminal drops below the ISO 14443 power threshold.
- An audio DAC's I²S output uses a 100 nH chip inductor as a simple low-pass filter bead before the I/V converter: at audio frequencies it is invisible, but above 50 MHz it attenuates switching-clock harmonics that would otherwise corrupt the SNR.
A short history
A chip inductor is a compact surface-mount inductor that stores energy in a magnetic field. The small package is useful in radio-frequency and wireless circuits. Its construction and core material affect its behaviour, so the package size alone does not tell you its inductance, losses or useful frequency range.
Good to know
- Wirewound chip inductors have the highest Q (lowest loss) at the cost of larger footprint; multilayer ceramic chip inductors fit in 0201 packages but with lower Q.
- RF matching networks live or die by inductor Q — every dB lost in the matching network is a dB lost in receive sensitivity.
- 5G mmWave designs increasingly use planar spiral inductors etched into the PCB rather than discrete chips, because losses at 28 GHz overwhelm even the best wirewound.