Inductors & Thermistors
Power inductors, ferrites, and NTCs: saturation vs rated current and B-constants.
Written and verified by John Merton · verified 2026-07-14
Inductors store energy in a magnetic field; thermistors change resistance with temperature. This category covers power inductor selection for switching converters (saturation current vs RMS current rating) and NTC thermistor selection (B-constant, resistance at 25 °C, and the voltage-divider math).
How to choose
The axes below are the criteria you actually weigh when selecting a part in this category.
- Saturation current vs RMS current rating
- Saturation current is where inductance drops 20–30 %. RMS current is the thermal limit. In a buck converter, the inductor must handle the peak current without saturating and the RMS current without overheating.
- Inductor DCR and core losses at switching frequency
- DCR causes I²R loss. Core losses increase with frequency. At 1 MHz, core loss can exceed copper loss. Check the inductor's loss curves at your switching frequency and current.
- NTC B-constant and the voltage divider math
- An NTC thermistor's resistance follows R(T) = R25 × exp(B × (1/T − 1/298.15)). The voltage divider output is nonlinear; the datasheet gives a resistance table. Pick the pull-up resistor to center the ADC range at your temperature of interest.
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Compare specs
Parts in this guide verified against manufacturer datasheets; latest 2026-07-14.
| MPN | Package | Lifecycle | Headline spec |
|---|---|---|---|
| BLM18AG601SN1 | 1608 metric / 0603 inch SMD ferrite bead | Active | Impedance: 600 ohm +/-25% at 100 MHz |
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