NXP Semiconductors BF904WR,135

Overview

BF904WR from NXP Semiconductors is an N-channel dual-gate MOSFET in SOT343R package, designed for low-noise RF amplification up to 1 GHz with 25 mS forward transfer admittance, 2.2 pF gate-1 input capacitance, and 2 dB noise figure at 800 MHz - deployed in VHF/UHF TV tuners and professional communications equipment operating from 3–7 V supply.

For engineers reviewing the BF904WR datasheet, BF904WR pinout, BF904WR application, or BF904WR equivalent, this page delivers verified specifications, validated pin functions, confirmed VHF/UHF tuner use cases, and two technically documented alternative dual-gate MOSFETs for AGC-stable RF front-end design.

Technical Context

The BF904WR integrates source-substrate interconnection and an internal bias circuit to maintain cross-modulation performance during automatic gain control (AGC). Its dual-gate architecture enables independent control of transconductance and input impedance - gate 1 (G1) serves as signal input while gate 2 (G2) acts as AGC voltage terminal at 4 V typical bias.

It operates as an enhancement-mode device with gate threshold voltages of 0.3–1.0 V (G1) and 0.3–1.2 V (G2), supports pulsed RF operation up to 1 GHz, and achieves stable 8–13 mA drain current under V_DS = 5 V, V_G2-S = 4 V, and R_G1 = 120 kΩ conditions.

Key Specifications

Pinout & Package

Package: SOT343R - plastic microminiature surface-mount package with reverse pinning (top view: Pin 1 = source/bulk, Pin 2 = drain, Pin 3 = gate 2, Pin 4 = gate 1), 1.35 mm × 1.15 mm footprint, 0.45 mm height.

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 extended bandwidth at the cost of higher noise above 800 MHz, while BF981,115 provides superior VHF noise performance but requires PCB redesign due to reversed gate pinning and delivers lower gain at UHF frequencies.

Availability

BF904WR is available at Aetrix Electronics and suitable for television tuner modules, professional UHF radio receivers, and RF test equipment requiring stable component supply with full traceability and long-term lifecycle support.

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-voltage, low-noise dual-gate amplifier applications in broadcast and professional wireless equipment.

FAQ

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

The BF904WR has a maximum drain-source voltage (V_DS) rating of 7 V, as defined in the Absolute Maximum Ratings table. This value must not be exceeded under any operating condition, including transient spikes, to prevent permanent device damage. The BF904WR is intended for low-voltage RF amplifier stages where supply rails remain within 3–7 V, such as in battery-powered tuners or 5 V fixed-rail receiver front-ends.

How does the BF904WR achieve stable cross-modulation performance during AGC operation?

The BF904WR achieves stable cross-modulation performance during AGC by integrating an internal bias circuit and interconnecting source and substrate terminals. This configuration maintains constant channel charge distribution as gate 2 (G2) voltage varies from 0–4 V, preventing gain-induced distortion. Measured data shows unwanted voltage remains below −110 dBμV across 40 dB of gain reduction - a key behavior confirmed in Figure 5 of the BF904WR datasheet.

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

The BF904WR has a typical noise figure of 2 dB at 800 MHz, measured under conditions of V_DS = 5 V, V_G2-S = 4 V, I_D = 10 mA, and optimal source impedance matching. This value is explicitly listed in the Dynamic Characteristics table on page 4 of the official NXP datasheet and reflects its suitability for UHF terrestrial TV signal amplification where low added noise is critical.

Can the BF904WR be used in a 3.3 V supply application?

Yes, the BF904WR is rated for operation from 3 V minimum supply voltage and is specifically optimized for 5 V systems, but functions reliably at 3.3 V. At 3.3 V, drain current reduces to approximately 5–8 mA (per Fig.12), forward transfer admittance drops to ~18 mS, and noise figure increases slightly - all within usable limits for low-power portable tuners. System validation is recommended for gain flatness and AGC linearity at reduced V_DS.

What is the thermal resistance from junction to ambient (R_{th j-a}) for the BF904WR in standard mounting?

The BF904WR has a thermal resistance from junction to ambient (R_{th j-a}) of 350 K/W when mounted on a standard printed-circuit board, as specified in the Thermal Characteristics table. This value assumes no additional copper pour or thermal vias; adding 25 mm² of 2-oz copper connected to the source pad reduces R_{th j-a} by ~30%. The BF904WR's 150 °C maximum junction temperature allows operation up to +70 °C ambient with appropriate derating per Figure 2.