NXP Semiconductors BLS2731-10,114

Overview

BLS2731-10 from Philips Semiconductors is an NPN silicon planar epitaxial microwave power transistor in a flanged ceramic SOT445C package, designed for common-base class-C pulsed operation at 2.7–3.1 GHz. It delivers 12.5 W output power with 10 dB power gain and 45% collector efficiency at V_CB = 40 V, tp = 100 µs, δ = 10%, and is optimized for radar transmitter stages requiring rugged pulsed RF amplification.

For engineers reviewing the BLS2731-10 datasheet, BLS2731-10 pinout, BLS2731-10 application, or BLS2731-10 equivalent, key selection criteria include its 75 V V_CBO, 1.5 A peak collector current, 1.2 K/W junction-to-heatsink thermal impedance, internal emitter ballasting, and gold metallization for reliability in high-stress pulsed RF environments.

Technical Context

The BLS2731-10 employs an interdigitated emitter-base structure and multicell geometry to enhance emitter efficiency and distribute thermal load across parallel transistor cells. Its internal input/output matching networks simplify integration into 50 Ω systems without external tuning components at 2.7–3.1 GHz.

Operating in common-base configuration with base tied to the flange (heatsink), it leverages low thermal impedance (1.2 K/W) and emitter ballasting resistors to withstand pulse-induced thermal stress and secondary breakdown. The SOT445C package uses a beryllium oxide (BeO) ceramic cap for superior thermal conduction-handling up to 145 W pulsed dissipation at T_mb = 25 °C.

Key Specifications

Pinout & Package

SOT445C is a flanged hermetic ceramic package with two mounting holes and three terminals: collector (pin 1), emitter (pin 2), and base (pin 3), where the base is internally connected to the metal flange serving as both electrical reference and thermal path to heatsink. The BeO ceramic cap ensures high thermal conductivity but requires handling precautions per safety notice.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar microwave pulsed power amplifier applications.

Compared with MRF454B and BLW86, the BLS2731-10 uniquely combines hermetic ceramic packaging, internal matching, and 12.5 W output in a flange-mounted form factor-making it optimal for field-deployable radar systems where reliability, thermal robustness, and rapid integration are prioritized over raw power scaling or wideband flexibility.

Availability

BLS2731-10 is available at Aetrix Electronics and suitable for radar transmitter stages, pulsed RF test equipment, and electronic warfare jammer modules requiring stable component supply with traceable sourcing and long-lifecycle support.

Supply support for BLS2731-10 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

Philips Semiconductors (now NXP Semiconductors) is a global leader in high-frequency discrete semiconductors, with deep heritage in RF power devices for defense and aerospace applications.

The BLS2731-10 belongs to Philips' microwave power transistor product line, engineered specifically for rugged, high-efficiency pulsed amplification in X-band radar systems where thermal stability, reliability, and ease of integration are mission-critical.

FAQ

What is the maximum safe operating junction temperature for the BLS2731-10?

The BLS2731-10 has a maximum operating junction temperature (T_j) of 200 °C, as specified in its limiting values table. This rating assumes proper heatsinking via the flange and adherence to pulsed operating conditions (tp ≤ 100 µs, δ ≤ 10%). Exceeding this temperature risks permanent degradation of the silicon die and gold metallization. For sustained reliability, thermal design should target T_j ≤ 175 °C under worst-case ambient and duty-cycle conditions. The BLS2731-10's 1.2 K/W thermal impedance enables this with appropriate copper heatsink mass.

Does the BLS2731-10 require external matching networks for operation at 2.9 GHz?

No-the BLS2731-10 integrates internal input and output matching networks optimized for the 2.7–3.1 GHz band, enabling direct 50 Ω interface in common-base class-C circuits without external tuning components. Application Fig.8 confirms a minimal external network (only DC blocking and bias chokes) is needed. However, fine-tuning may be required for maximum efficiency or harmonic suppression in production systems. The BLS2731-10's matching is validated across temperature and process variation, making it more robust than discrete-matched alternatives like BLW86.

Why does the BLS2731-10 datasheet warn about beryllium oxide (BeO)?

The BLS2731-10 uses a beryllium oxide (BeO) ceramic cap in its SOT445C package for exceptional thermal conductivity (≈280 W/m·K). While fully encapsulated and safe during normal operation, mechanical damage to the BeO disc can release toxic dust. Handling, rework, or disposal must follow strict industrial hygiene protocols: avoid grinding, drilling, or breaking the package; wear NIOSH-approved respirators if damage is suspected; and dispose as chemical/special waste per local regulations. The BLS2731-10 remains safe when mounted and operated per spec-this warning applies only to physical compromise of the ceramic.

Can the BLS2731-10 be used in continuous-wave (CW) mode?

No-the BLS2731-10 is characterized and rated exclusively for pulsed operation (tp ≤ 100 µs, δ ≤ 10%). Its 145 W total power dissipation rating applies only under those conditions. In CW mode, junction temperature would rapidly exceed 200 °C even with aggressive heatsinking, risking thermal runaway and failure. The device's multicell geometry and emitter ballasting are optimized for transient thermal distribution-not steady-state conduction. For CW X-band amplification, alternative devices such as the MRF454B or BLW97 must be evaluated. The BLS2731-10 must not be substituted in CW designs.

What is the role of the flange connection in the BLS2731-10's circuit operation?

In the BLS2731-10, the flange is electrically connected to pin 3 (base) and serves as the common reference node for the common-base amplifier configuration. This eliminates the need for a separate base terminal and provides a low-inductance, low-thermal-resistance path to the heatsink. RF grounding of the base via the flange stabilizes the operating point, minimizes parasitic oscillation, and enhances power gain consistency. Mechanical mounting torque and surface flatness directly impact both RF performance and thermal reliability-improper flange contact degrades Z_{th j-h} and can cause localized hot spots. The BLS2731-10's functionality depends critically on correct flange bonding.