NXP Semiconductors BF904AR,215

Overview

BF904AR from NXP Semiconductors is an N-channel dual-gate MOSFET designed for low-noise, high-gain RF amplification in VHF/UHF tuners and professional communications equipment. It operates at 5 V supply, delivers 25 mS forward transfer admittance (|y_fs

For engineers reviewing the BF904AR datasheet, BF904AR pinout, BF904AR application, or BF904AR equivalent, this page provides verified package mapping (SOT143R), confirmed dual-gate RF amplifier functionality, validated AGC-compatible cross-modulation performance, and real-world tuner design context - all extracted from NXP's official Product Specification Rev. 04 (2007).

Technical Context

The BF904AR implements an enhancement-mode dual-gate structure with source and substrate internally connected, enabling independent bias control of gate 1 (signal input) and gate 2 (AGC voltage control). Its short-channel architecture optimizes the |y_fsig1-ss ratio for broadband gain up to 1 GHz.

It supports automatic gain control via gate 2 while maintaining low noise figure (2 dB @ 800 MHz) and superior cross-modulation suppression - critical for multi-channel VHF/UHF reception where signal integrity under varying input levels is essential.

Key Specifications

Pinout & Package

SOT143R plastic surface-mounted package (reverse pinning), 4-lead, dimensions: 3.0 × 1.4 × 1.1 mm (D × E × A), with 0.95 mm lead pitch. Pin 1 = source, 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 BF904AR, BF998 offers higher RF gain and bandwidth but requires board redesign due to SOT143B pinout; MRF901LT1G provides greater output power but eliminates AGC functionality entirely - making BF904AR uniquely suited for legacy VHF/UHF tuner designs requiring integrated analog gain control.

Availability

BF904AR is available at Aetrix Electronics and suitable for television tuner modules, professional wireless microphone receivers, VHF airband communications equipment, and RF test instrument signal paths requiring stable component supply and long-lifecycle support.

Supply support for BF904AR 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 headquartered in Eindhoven, Netherlands, specializing in secure connectivity solutions for automotive, industrial, and consumer applications.

The BF904AR belongs to NXP's legacy RF transistor product line, engineered specifically for high-performance, low-noise dual-gate amplification in analog and early-digital broadcast receiver systems.

FAQ

What is the correct pinout configuration for BF904AR?

The BF904AR uses the SOT143R package with reverse pinning: Pin 1 = source, Pin 2 = drain, Pin 3 = gate 2 (AGC control), Pin 4 = gate 1 (RF input). This differs from the BF904A (SOT143B, standard pinout) - using the wrong footprint causes functional failure. Always verify against Fig.2 in NXP's BF904A_AR_AWR_N_4 datasheet.

Does BF904AR support automatic gain control (AGC), and how is it implemented?

Yes, BF904AR supports analog AGC via gate 2. Applying 0–5 V to gate 2 linearly reduces gain while maintaining low noise and cross-modulation performance - confirmed by Fig.6 (gain reduction vs. V_AGC) and Fig.7 (cross-modulation vs. gain reduction) in the official datasheet. Gate 1 remains the high-impedance RF input.

What is the maximum operating frequency supported by BF904AR?

The BF904AR is characterized for low-noise amplification up to 1 GHz, with verified performance including 2 dB noise figure at 800 MHz and usable |y_{fs20 mS at 1 GHz (per Fig.19). Its S-parameter data extends to 3 GHz, but practical RF gain rolls off above 1.2 GHz - making it ideal for VHF/UHF bands (30–900 MHz).}

Can BF904AR be used with a 3.3 V supply instead of 5 V?

No - BF904AR is explicitly designed for 5 V operation (per "FEATURES" section). At 3.3 V, drain current drops significantly (see Fig.14), |y_fsDS = 5 V and V_G2-S = 4 V for all dynamic characteristics; operation below 4.5 V is unsupported and risks instability.

How does BF904AR compare to BF904AWR in terms of package and performance?

BF904AR (SOT143R) and BF904AWR (SOT343R) share identical electrical specifications but differ in package: SOT143R is 3.0 × 1.4 mm; SOT343R is smaller (2.2 × 1.35 mm) with same 4-pin reverse pinout. Thermal resistance (R_{th j-s} = 200 K/W) and all RF parameters are identical - choice depends solely on PCB space constraints and assembly capability.