Small-signal NPN for L-band through C-band front ends
The NXP BFU610F,115 is an NPN silicon RF transistor in a SOT-343F surface-mount package, designed for low-noise amplifier stages from the 1.5 GHz ISM band up through 5.8 GHz WLAN and C-band satellite downlinks. Its 15 GHz transition frequency (fT) gives enough gain headroom for a single-stage LNA to deliver 13.5 dB to 23.5 dB of gain across that range, depending on bias and matching network. Noise figure runs 0.9 dB typical at 1.5 GHz and 1.7 dB at 5.8 GHz, placing it in the low-noise tier for a general-purpose small-signal transistor — useful for receiver front ends where the first-stage NF dominates the cascaded noise budget. Collector-emitter breakdown is rated at 5.5 V maximum with a 10 mA collector current ceiling, so this part stays in low-voltage, low-current signal-chain roles — not a driver or power stage.
The 13.5 dB to 23.5 dB gain range is bias- and frequency-dependent; a designer typically targets the lower end at 5.8 GHz and the higher end at 1.5 GHz, with the gain roll-off following the 6 dB/octave slope above fT/10. The 90 minimum DC current gain (hFE) at 1 mA, 2 V confirms the transistor has healthy beta for biasing with a simple collector-feedback or emitter-degeneration network. The 0.9 dB NF at 1.5 GHz is competitive for a low-cost SOT-343F part — expect to give back 0.1–0.2 dB in a real PCB layout with a standard FR-4 microstrip and a 0402 matching inductor. At 5.8 GHz the 1.7 dB NF is still usable for a second-stage LNA or a downconverter mixer buffer, though a dedicated pHEMT would beat it by 0.5 dB or more.
Package and mounting: SOT-343F
The SOT-343F (4-lead flat-pack, supplier device package 4-DFP) is a standard footprint for small-signal RF transistors. The collector is on the backside paddle — ensure the PCB land pattern includes a thermal via or a solid ground-plane connection under the part to keep junction temperature below the 150°C (TJ) maximum at the 136 mW power dissipation limit. Surface-mount assembly per standard lead-free reflow profiles; the part is ROHS3 compliant. No special bake-out required if the moisture-sealed reel is used within the floor-life window.
Lifecycle and supply position
No official second-source or pin-compatible replacement is listed in the NXP portfolio for this exact order code. If dual-sourcing is required, a designer would need to evaluate a functionally similar NPN RF transistor with matching SOT-343F footprint and comparable fT and NF specs — the BFU610F itself is the active baseline.