NXP Semiconductors BF904WR,115

Overview

BF904WR from NXP Semiconductors is an N-channel dual-gate MOSFET in SOT343R package, designed for 5 V supply operation with 25 mS typical forward transfer admittance, 2.2 pF gate-1 input capacitance, and 2 dB noise figure at 800 MHz - used as low-noise RF amplifier in VHF/UHF TV tuners and professional communications equipment.

For engineers reviewing the BF904WR datasheet, BF904WR pinout, BF904WR application, or BF904WR equivalent, this page delivers verified electrical parameters, validated SOT343R pin mapping, confirmed AGC-compatible cross-modulation performance, and real-world RF gain control use cases at 50–1000 MHz.

Technical Context

The BF904WR integrates two independent gates (G1 and G2) with source and substrate internally connected, enabling precise RF gain control via G2 while G1 serves as signal input - its enhancement-mode structure requires no external bias resistors for basic operation. The internal bias circuit ensures stable cross-modulation performance during automatic gain control (AGC) transitions.

Designed for common-source configuration, it operates at V_DS = 5 V, I_D = 10 mA, and V_G2-S = 4 V, delivering 2.42× typical |s₂₁| magnitude at 40 MHz and maintaining usable gain up to 1 GHz. Its 25 fF reverse transfer capacitance minimizes feedback instability in high-frequency amplifiers.

Key Specifications

Pinout & Package

BF904WR uses the plastic microminiature SOT343R surface-mount package (2.2 × 1.35 × 0.95 mm), featuring reverse pinning: Pin 1 = source/bulk, Pin 2 = drain, Pin 3 = gate 2, Pin 4 = gate 1.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BF904WR, BF998,115 offers higher RF gain and bandwidth at the expense of slightly increased noise figure (2.3 dB), while NE85633 provides higher power handling but eliminates dual-gate functionality - making BF904WR the optimal choice for compact, AGC-integrated VHF/UHF tuners.

Availability

BF904WR is available at Aetrix Electronics and suitable for television tuner modules, professional UHF transceivers, and VHF aircraft band receivers requiring stable component supply across extended production cycles.

Supply support for BF904WR 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 BF904WR belongs to NXP's legacy RF transistor product line, engineered specifically for low-noise, dual-gate amplifier applications in broadcast and professional wireless equipment operating from 30 MHz to 1 GHz.

FAQ

What is the maximum drain-source voltage rating for BF904WR?

The BF904WR has a maximum drain-source voltage (V_DS) rating of 7 V, as specified in the Limiting Values table. This rating applies under all operating conditions and must not be exceeded to prevent permanent device damage. The BF904WR is intended for low-voltage RF amplifier applications such as TV tuners powered from 5 V supplies, where headroom above nominal rail is limited.

How does the dual-gate structure of BF904WR improve AGC performance compared to single-gate MOSFETs?

The BF904WR's dual-gate architecture separates signal path (gate 1) from gain control (gate 2), allowing AGC voltage applied to gate 2 to modulate transconductance without injecting distortion into the RF input path. This results in superior cross-modulation suppression - measured at <−110 dBµV for 1% distortion - unlike single-gate devices that require external diode networks and suffer from gain-control nonlinearity. The BF904WR achieves this with no additional components.

What is the typical noise figure of BF904WR and at what frequency is it measured?

The BF904WR exhibits a typical noise figure (F) of 2 dB at 800 MHz, measured under standard conditions: V_DS = 5 V, V_G2-S = 4 V, I_D = 10 mA, and source impedance matched to optimum noise impedance. At 200 MHz, the noise figure drops to 1 dB, confirming its suitability for VHF low-noise amplification. These values are validated in Table 2 of the official NXP datasheet dated 2010 Sep 15.

Can BF904WR operate reliably at supply voltages below 5 V?

Yes, the BF904WR is characterized for operation across 3–7 V supply range per its Applications section, though it is "specially designed for use at 5 V supply voltage." At 3 V, forward transfer admittance drops to ~18 mS and noise figure increases to ~2.5 dB, but functional amplification remains viable in battery-powered UHF receivers. Full specification compliance (e.g., 25 mS |y_fs|, 2 dB F) is guaranteed only at 5 V V_DS and 4 V V_G2-S.

What is the thermal resistance from junction to ambient for BF904WR, and how does it affect PCB layout?

The BF904WR has a thermal resistance from junction to ambient (R_{th j-a}) of 350 K/W when mounted on a standard PCB, as stated in the Thermal Characteristics table. This high value means even modest power dissipation (e.g., 100 mW) causes ~35 °C junction rise above ambient - requiring careful copper pour design under the source pad (Pin 1) and avoidance of enclosed ground planes. Derating begins above 50 °C ambient, per Figure 2.