NXP Semiconductors BF908,215

Overview

BF908,215 from NXP Semiconductors is a depletion-mode dual-gate MOSFET in SOT143 package, designed as a low-noise RF amplifier for VHF/UHF front-ends. It delivers 43 mS typical forward transfer admittance, 3.1 pF input capacitance at gate 1, and 1.5 dB noise figure at 800 MHz - enabling high-gain, low-distortion amplification in 12 V TV tuners and professional comms receivers.

For engineers reviewing the BF908,215 datasheet, BF908,215 pinout, BF908,215 application, or BF908,215 equivalent, this device requires attention to gate protection (integrated back-to-back diodes), thermal derating above 50 °C ambient, dual-bias configuration (VG2-S = 4 V typical), and S-parameter validation for 50–1000 MHz matching networks.

Technical Context

This dual-gate MOSFET operates in common-source configuration with gate 2 biased at fixed DC potential (typically 4 V) to set transconductance, while gate 1 serves as the RF signal input. Its short-channel structure yields high y_fs/C_ig1-s ratio (≥13.9 mS/pF), supporting broadband gain stability up to 1 GHz.

Integrated anti-static protection includes back-to-back diodes between each gate and source, enabling robust handling without external clamping. The device exhibits strong temperature dependence of y_fs, dropping ~15% from 25 °C to 125 °C junction temperature - requiring thermal-aware bias design in enclosed tuners.

Key Specifications

Pinout & Package

BF908,215 is housed in a plastic microminiature SOT143 package (3.0 × 1.4 × 0.95 mm), optimized for RF layout with low-inductance source bonding and symmetrical lead frame.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BF908,215, BF998,215 offers higher gain and lower input capacitance for extended UHF coverage, while MRF901LT1G trades dual-gate noise control for higher output power and ruggedness - making BF908,215 optimal for cost-sensitive, space-constrained VHF/UHF tuner LNA designs.

Availability

BF908,215 is available at Aetrix Electronics and suitable for television tuner modules, professional wireless audio receivers, VHF communications equipment, and ISM band signal detectors requiring stable component supply and long-term obsolescence support.

Supply support for BF908,215 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 leader focused on secure connectivity solutions for automotive, industrial, and consumer applications, with core expertise in RF, analog, and mixed-signal ICs.

The BF908,215 belongs to NXP's legacy RF transistor product line, engineered specifically for high-performance, low-cost VHF/UHF amplifier stages in broadcast and professional communications equipment.

FAQ

What is the maximum safe drain-source voltage for BF908,215?

The absolute maximum drain-source voltage (V_DS) for BF908,215 is 12 V, as defined in the limiting values table. Exceeding this rating - even transiently - risks permanent die damage due to avalanche breakdown. In practice, designs should operate at ≤10 V to ensure margin against supply ripple and switching transients, especially in unregulated 12 V tuner supplies.

How does the dual-gate structure of BF908,215 improve noise performance compared to single-gate MOSFETs?

The dual-gate architecture of BF908,215 isolates the RF signal path (gate 1) from the DC bias control path (gate 2), reducing gate-induced noise and minimizing feedback through C_rs. This separation allows gate 2 to be stabilized at an optimal voltage (4 V) for lowest noise figure (1.5 dB at 800 MHz), while gate 1 remains highly sensitive to incoming RF - a capability single-gate devices cannot replicate without external neutralization.

Can BF908,215 be used in 2.4 GHz applications despite its 1 GHz specified bandwidth?

BF908,215 is characterized up to 1000 MHz in its datasheet, with scattering parameters and noise data confirmed only through 1 GHz. While some designers use it as a fundamental amplifier up to 1.2 GHz (e.g., for 2.4 GHz harmonic mixing), operation beyond 1 GHz lacks validated S-parameters or noise data - and C_rs and C_ig1-s parasitics degrade gain flatness and matching predictability. For 2.4 GHz, NXP recommends dedicated GaAs or SiGe alternatives.

What is the purpose of the integrated back-to-back diodes in BF908,215?

The integrated back-to-back diodes between each gate (G1 and G2) and the source (s,b) in BF908,215 provide on-chip electrostatic discharge (ESD) protection rated to ±10 mA gate current. They clamp transient voltages during handling or PCB assembly, eliminating the need for external diode networks - a key reliability feature for high-volume tuner manufacturing where manual handling and reflow soldering pose ESD risks.

How does thermal derating affect BF908,215 performance in enclosed tuner modules?

BF908,215 has a thermal resistance of 500 K/W and must be derated linearly above 50 °C ambient: power dissipation drops by 2.0 mW per °C rise. In sealed tuner modules reaching 70 °C internal ambient, P_tot falls to 160 mW - reducing maximum sustainable I_D from 15 mA to ~12 mA and lowering y_fs by ~9%, directly impacting gain and noise figure. Thermal vias under the drain pad are mandatory for compliance.