NXP Semiconductors BF908WR,115

Overview

BF908WR from NXP Semiconductors is an N-channel dual-gate MOSFET in SOT343R package, designed for low-noise RF amplification up to 1 GHz. It features forward transfer admittance (|y_fs|) of 36–50 mS, input capacitance at gate 1 of 2.4–4 pF, and noise figure of 1.5 dB at 800 MHz - optimized for VHF/UHF tuners and professional communications equipment with 12 V supply.

For engineers reviewing the BF908WR datasheet, BF908WR pinout, BF908WR application, or BF908WR equivalent, key selection considerations include its dual-gate architecture for gain control, integrated back-to-back gate protection diodes, thermal resistance (R_{th j-a} = 350 K/W), and specified operation up to 150 °C junction temperature.

Technical Context

The BF908WR is a depletion-mode dual-gate MOSFET where gate 1 (g1) serves as the signal input and gate 2 (g2) acts as a DC bias or gain-control terminal. Its short-channel structure delivers high |y_fs|/C_ig1-s ratio, enabling stable broadband amplification with minimal feedback.

It operates with V_DS ≤ 12 V, I_D ≤ 40 mA, and P_tot ≤ 300 mW at T_amb ≤ 45 °C. Static characteristics include V_(BR)G1-SS ≥ 8 V and V_PG1-S ≤ −2 V, confirming robust gate-source breakdown and cut-off behavior under typical tuner bias conditions.

Key Specifications

Pinout & Package

BF908WR is housed in a plastic microminiature SOT343R surface-mount package with reverse pinning (top view: Pin 1 = source/bulk, Pin 2 = drain, Pin 3 = gate 2, Pin 4 = gate 1). The package includes integrated back-to-back diodes between each gate and source for ESD protection.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BF908WR, BF998,115 offers higher gain and bandwidth in identical packaging, while NE3210M02 provides superior high-frequency performance at the cost of dual-gate functionality and integrated protection - making BF908WR the preferred choice for cost-sensitive, ESD-prone VHF/UHF tuner applications requiring gain adjustability.

Availability

BF908WR is available at Aetrix Electronics and suitable for television tuners, professional UHF communications equipment, and FM radio receiver RF amplifiers requiring stable component supply and long-term obsolescence management.

Supply support for BF908WR 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 BF908WR belongs to NXP's legacy RF transistor product line, engineered specifically for low-noise, dual-gate amplification in broadcast and professional VHF/UHF equipment - emphasizing ESD robustness, thermal stability, and compact packaging for tuner module integration.

FAQ

What is the maximum drain-source voltage rating for the BF908WR?

The BF908WR has a maximum drain-source voltage (V_DS) rating of 12 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. Operation at or near this limit requires verification of power dissipation and thermal derating per Figure 2 in the datasheet, especially above ambient temperatures of 45 °C.

Does the BF908WR include built-in ESD protection?

Yes, the BF908WR integrates back-to-back diodes between each gate (g1 and g2) and the source terminal to protect against excessive input voltage surges. This internal protection limits gate current to ±10 mA and helps prevent electrostatic damage during handling or transient events in tuner circuits - though external handling precautions (e.g., antistatic packaging and grounding) remain essential.

What is the typical noise figure of the BF908WR at 800 MHz?

The BF908WR exhibits a typical noise figure (F) of 1.5 dB at 800 MHz, measured under conditions of optimal source admittance (GS = GS_opt) and optimal bias (BS = BS_opt). This value is confirmed in the Dynamic Characteristics section and makes the BF908WR suitable for low-noise amplification in UHF broadcast and communications receivers.

Can the BF908WR be used in place of the BF998,115?

The BF908WR is not a direct replacement for the BF998,115 due to differences in forward transfer admittance (43 mS vs. 55 mS typ) and input capacitance (3.1 pF vs. 2.1 pF typ). While both share the SOT343R package and pinout, the BF998,115 delivers higher gain and bandwidth. System-level validation is required before substitution, particularly in applications demanding >1 GHz operation or tighter noise performance.

What is the thermal resistance from junction to ambient for the BF908WR?

The BF908WR 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 stated in the Thermal Characteristics section. This value assumes no additional heatsinking and dictates minimum copper area requirements on the source pad to maintain T_j ≤ 150 °C under full 300 mW power dissipation.