NXP Semiconductors BF909WR,115

Overview

BF909WR from NXP Semiconductors is an N-channel dual-gate MOSFET in SOT343R package, designed for 5 V supply operation with 43 mS typical forward transfer admittance, 3.6 pF input capacitance at gate 1, and 2.0 dB noise figure at 800 MHz - deployed as low-noise RF amplifier in VHF/UHF tuners and professional communications equipment.

For engineers reviewing the BF909WR datasheet, BF909WR pinout, BF909WR application, or BF909WR equivalent, key selection criteria include dual-gate AGC stability, cross-modulation performance under gain reduction, RF noise figure below 2.8 dB up to 1 GHz, and thermal resistance of 350 K/W junction-to-ambient.

Technical Context

This enhancement-mode MOSFET integrates source-substrate interconnection and internal bias circuitry to maintain superior cross-modulation performance during automatic gain control (AGC) operation. Its dual-gate architecture enables independent control of RF signal path (gate 1) and AGC voltage (gate 2), with gate 2 held at 4 V for optimal noise and gain trade-off.

Designed for high-frequency amplification up to 1 GHz, the BF909WR delivers stable small-signal gain with minimal reverse transfer capacitance (30–50 fF) and exhibits low gate leakage (≤50 nA per gate) at 5 V bias. It operates within a 3–7 V supply range while maintaining specified noise figure and forward admittance across its 15 mA nominal drain current operating point.

Key Specifications

Pinout & Package

Package: SOT343R - plastic microminiature surface-mounted package with reverse pinning (top view: Pin 1 = source/bulk, Pin 2 = drain, Pin 3 = gate 2, Pin 4 = gate 1), footprint dimensions 2.2 × 1.35 × 0.95 mm, 4-lead leadless design optimized for RF layout integrity.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar dual-gate MOSFET amplifier applications.

Compared with BF998,115 and MRF901LT1G, the BF909WR uniquely combines sub-2.5 dB noise figure, integrated dual-gate AGC biasing, and SOT343R RF layout compatibility - making it irreplaceable in cost-sensitive, space-constrained VHF/UHF tuner designs requiring guaranteed cross-modulation immunity.

Availability

BF909WR is available at Aetrix Electronics and suitable for television tuners, professional UHF radio receivers, VHF aircraft communication systems, and RF test equipment requiring stable component supply with full traceability and long-term lifecycle support.

Supply support for BF909WR includes scheduled delivery planning, volume procurement assistance, BOM continuity management, traceable sourcing, and lifecycle availability coordination for OEM customers, industrial embedded developers, connected-device designers, and electronics production programs.

Manufacturer

NXP Semiconductors is a global semiconductor company specializing in high-performance RF, analog, and mixed-signal solutions for consumer, industrial, and communications markets.

The BF909WR belongs to NXP's legacy RF transistor product line, engineered specifically for low-voltage, low-noise dual-gate amplification in broadcast and professional wireless equipment operating up to 1 GHz.

FAQ

What is the maximum operating frequency supported by the BF909WR?

The BF909WR is characterized up to 1000 MHz with verified scattering parameters and maintains usable forward transfer admittance (|y_fs| ≥ 2.3 mS) and noise figure (F ≤ 2.8 dB) through 800 MHz. Its design intent targets VHF and UHF bands (30–900 MHz), and performance beyond 1 GHz is not specified in the official NXP data sheet. For 1 GHz+ applications, consult the BF909WR S-parameter tables in the datasheet.

Can the BF909WR operate reliably at 3 V supply voltage?

Yes - the BF909WR is rated for 3–7 V supply operation per its Applications section and Quick Reference Data. At 3 V drain-source voltage, forward transfer admittance drops and noise figure increases versus the 5 V optimum point, but the device remains functional in low-voltage tuner modules. Derating curves and static characteristics confirm stable ID and VG(th) behavior down to 3 V, though gain and noise performance are reduced.

How does the BF909WR achieve superior cross-modulation performance during AGC?

The BF909WR achieves superior cross-modulation performance via internal source-bulk interconnection and dedicated gate 2 biasing (typically 4 V), which stabilizes the channel potential during gain reduction. This architecture minimizes intermodulation distortion generation when AGC voltage varies - demonstrated by < −90 dBμV unwanted voltage at 1% cross-modulation in the datasheet's Fig.3. No external components are required to realize this behavior.

Is the SOT343R package of the BF909WR RoHS compliant?

Yes - the BF909WR in SOT343R package is RoHS compliant per NXP's product status documentation dated 2010 Sep 15, which confirms production status and compliance with EU Directive 2002/95/EC. The package uses lead-free terminations and halogen-free molding compound, consistent with NXP's standard environmental specifications for surface-mount discrete semiconductors.

What is the recommended gate 1 bias network for optimal noise figure in the BF909WR?

The BF909WR datasheet specifies optimal noise performance at V_DS = 5 V, V_G2-S = 4 V, I_D = 15 mA, with gate 1 biased via a 120 kΩ resistor to V_GG = 5 V (Fig.9–10). This configuration yields the documented 2.0 dB noise figure at 800 MHz. Deviations - especially lower gate 1 resistances - increase thermal noise and degrade F; values outside 100–150 kΩ require re-characterization per application conditions.