Active production, 27 µH wirewound for power and signal filtering
The Murata LQH43NN270J03L is an active-production drum core wirewound inductor in the LQH43 series, offering 27 µH inductance with ±5% tolerance in a standard 1812 (4532 Metric) surface-mount package. Rated for 300 mA continuous current with a maximum DC resistance of 1.1 Ω, this unshielded inductor suits low-to-moderate current filtering in DC-DC converter output stages, power supply rails, and signal conditioning circuits where the 27 µH value provides adequate ripple attenuation.
What the 27 µH and 300 mA ratings mean for your board
The 27 µH inductance at 1 MHz test frequency with a self-resonant frequency of 14 MHz means this inductor behaves as an inductor well into the low-MHz switching range — above 14 MHz the parasitic capacitance dominates and the impedance starts dropping, so keep the switching frequency below that ceiling for predictable filtering. The 300 mA current rating is the DC bias current at which the inductance typically drops by 10% due to core saturation — derate for ambient temperature above 85°C and for AC ripple current, which adds core heating beyond the DC heating from the 1.1 Ω DCR. A Q factor of 35 at 1 MHz indicates moderate energy efficiency at that frequency — acceptable for general-purpose filtering but not optimal for high-Q resonant tank circuits where you would typically look for Q above 50.
Temperature range and unshielded construction
Operating from -40°C to +105°C, the ferrite core material maintains stable inductance across the industrial temperature band — the core permeability drops above 100°C, so inductance may shift a few percent near the upper limit. Being unshielded, this inductor radiates a magnetic field that can couple into adjacent traces or components — keep sensitive analog or RF circuitry at least 5 mm away, or use a shielded variant from the same LQH43 family if cross-coupling becomes an issue in layout.