STMicroelectronics SD2904

Overview

SD2904 from STMicroelectronics is a gold-metallized N-channel MOSFET RF power transistor in common-source configuration, rated for 30 W output at 400 MHz under 28 V DC supply, with 9.5 dB minimum power gain and 45–55% drain efficiency - used in HF/VHF/UHF broadband amplifier stages for land-mobile radio transmitters.

For engineers reviewing the SD2904 datasheet, SD2904 pinout, SD2904 application, or SD2904 equivalent, key selection considerations include its 65 V V(BR)DSS rating, 1.75 °C/W junction-to-case thermal resistance, 47 pF Ciss, Class A/AB bias flexibility, and M113 hermetic metal-ceramic package suitability for high-reliability RF final-stage designs.

Technical Context

This device operates as a single-ended, common-source RF power amplifier with gold-metallized gate and source interconnects ensuring low contact resistance and stable high-frequency performance. Its 2–500 MHz frequency range, 5 A continuous drain current, and 100 W maximum power dissipation support robust large-signal operation in demanding RF power stages.

The SD2904 features voltage-controlled transconductance (gFS = 1.2 mho), low input capacitance (Ciss = 47 pF), and impedance-matched ZIN = 2.0 − j2.4 Ω at 400 MHz - enabling direct integration into 50 Ω systems with minimal external matching network complexity.

Key Specifications

Pinout & Package

M113 is a hermetically sealed, flanged metal-ceramic package with flat aluminum/copper heatsink interface and Dow Corning 340-compatible thermal compound requirement. Dimensions: 24.77 mm × 20.32 mm × 5.72 mm (0.975″ × 0.800″ × 0.225″).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MRF151G and BLF188XR, the SD2904 offers optimal balance of thermal performance, gain flatness, and ruggedness for mobile-grade 30 W UHF amplifiers - especially where 65 V breakdown margin and 10:1 VSWR survivability are mandatory.

Availability

SD2904 is available at Aetrix Electronics and suitable for land-mobile radio transmitters, UHF broadcast auxiliary links, VHF airband repeaters, and HF amateur radio linear amplifier modules requiring stable component supply across extended production lifecycles.

Supply support for SD2904 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, designing and manufacturing analog, power, and RF components for industrial, automotive, and communications markets.

The SD2904 belongs to ST's high-reliability RF power transistor product line, engineered specifically for ruggedized HF/VHF/UHF transmitter final stages where thermal stability, voltage margin, and load mismatch resilience are non-negotiable.

FAQ

What is the recommended gate bias voltage for Class AB operation at 400 MHz?

The SD2904 achieves optimal Class AB performance at IDQ = 50 mA, requiring VGS ≈ 2.8–3.2 V per the normalized VGS vs. Tc curve (GC82510). This bias point balances linearity and efficiency while maintaining thermal stability across −20°C to +80°C ambient conditions.

Can SD2904 be operated safely with a 50 V DC supply?

No - the absolute maximum V(BR)DSS is 65 V, but the electrical specifications (including POUT, GPS, and ηD) are validated only up to 28 V. Exceeding 28 V risks exceeding safe operating area limits and voids guaranteed RF performance per the November 1999 datasheet.

Is the M113 package RoHS-compliant?

The SD2904 was released in 1999 and predates RoHS legislation; its M113 package contains lead-based solder and gold-plated Kovar leads. STMicroelectronics does not classify it as RoHS-compliant, and no lead-free reflow profile is specified in the original documentation.

Does SD2904 require external gate protection diodes?

Yes - although IGSS is limited to 2 µA at VGS = 20 V, the device lacks integrated ESD protection. STMicroelectronics recommends placing back-to-back Schottky diodes (e.g., HSMS-2850) between gate and source to clamp transient voltages during hot insertion or antenna disconnect events.