3.9 µH wirewound inductor for signal filtering and DC-DC input/output
The Murata LQH31MN3R9J03L is a 3.9 µH drum core wirewound inductor in the LQH31 series, rated for 125 mA continuous current with a DC resistance of 1.5 Ohm. The 1.5 Ohm DCR means at full rated current the inductor dissipates about 23 mW as heat — negligible in most circuits, but the voltage drop across the winding matters for low-voltage rails where every millivolt counts. Unshielded construction means the magnetic field radiates from the core. Board layout should keep sensitive analog traces, low-level signal lines, or other magnetics at least a few millimeters away to avoid coupling. The ferrite core material gives stable inductance over frequency up to the self-resonant point of 35 MHz.
Frequency response and Q factor — where this inductor works best
With a Q factor of 35 at 8 MHz and a self-resonant frequency of 35 MHz, this inductor is well-suited for filtering and impedance matching in the low-MHz range — think EMI filter output stages, LC tank circuits below 10 MHz, or DC-DC converter input/output filters switching in the hundreds of kHz to low MHz. Above 35 MHz the inductor becomes capacitive and loses its inductive behavior. The inductance is tested at 1 MHz, which is the standard test frequency for this value range. The ±5% tolerance gives tighter control than the ±10% or ±20% grades common on power inductors — useful when the inductance value directly sets a filter cutoff or oscillator frequency.
Package and board assembly — 1206 SMD, tape and reel
The 1206 footprint is widely supported by pick-and-place equipment and reflow profiles; no special nozzle or handling required. Operating temperature range is -40°C to +85°C, covering commercial and most industrial indoor environments. Not rated for extended automotive under-hood temperatures or high-humidity outdoor exposure without conformal coating consideration.