STMicroelectronics SD2902

Overview

SD2902 from STMicroelectronics is a gold-metallized N-channel MOSFET RF power transistor in common-source configuration, rated for 15 W output at 400 MHz, 28 V DC supply, and 12.5 dB minimum power gain - designed for HF/VHF/UHF broadband amplifiers in land mobile radio and industrial RF heating systems.

For engineers reviewing the SD2902 datasheet, SD2902 pinout, SD2902 application, or SD2902 equivalent, key selection criteria include its 65 V V(BR)DSS rating, 2.5 A continuous drain current, 3.0 °C/W junction-to-case thermal resistance, gold metallization for reliability under thermal cycling, and verified performance across 2–500 MHz with Class A/AB bias flexibility.

Technical Context

The SD2902 operates as a single-ended, common-source RF power amplifier with gate-controlled transconductance (gFS = 0.6 mho) and optimized capacitance profile (CISS = 23 pF, COSS = 18 pF, CRSS = 3.5 pF at 1 MHz). Its ZIN = 2.6 − j6.5 Ω and ZDL = 7.8 + j10 Ω at 400 MHz enable direct matching into 50 Ω systems using discrete L-networks.

Thermal design is anchored by Rth(j-c) = 3.0 °C/W and Rth(c-s) = 0.30 °C/W with proper heatsinking, supporting stable operation up to Tj = 200 °C. Gate threshold voltage VGS(Q) ranges 1.0–6.0 V at ID = 30 mA, enabling precise quiescent current setting for linear Class AB operation.

Key Specifications

Pinout & Package

SD2902 uses the M113 hermetically sealed metal-can package (24.64–24.89 mm × 19.81–20.83 mm × 5.59–5.84 mm), with flat aluminum/copper heatsink mounting via flange (pin 1–4 layout).

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 SD2902 uniquely balances broadband HF–UHF coverage (2–500 MHz), hermetic reliability, and 15 W output in a thermally robust M113 package - making it optimal for legacy radio systems and industrial heating where wideband linearity and long-term stability are prioritized over peak frequency or power.

Availability

SD2902 is available at Aetrix Electronics and suitable for land mobile radio transmitters, UHF industrial RF heating systems, HF amateur radio amplifiers, and VHF broadcast auxiliary links requiring stable component supply across extended product lifecycles.

Supply support for SD2902 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, Switzerland, specializing in power management, analog, and RF solutions for industrial, automotive, and communications markets.

The SD2902 belongs to ST's legacy RF Power Transistor family, engineered specifically for ruggedized, high-reliability HF/VHF/UHF amplifier applications where hermetic sealing, gold interconnects, and thermal resilience are mandatory.

FAQ

What is the recommended gate biasing method for linear Class AB operation?

Set IDQ = 25 mA using a fixed VGS bias network derived from the VGS(Q) curve (1.0–6.0 V at 30 mA). Use a 10 kΩ potentiometer in series with a 100 nF bypass capacitor to adjust gate voltage while monitoring drain current with a milliammeter in series with the 28 V supply.

Can SD2902 be used in push-pull configuration?

Yes - the common-source topology and matched device parameters support push-pull use. Pair two SD2902s with 180° input phase shift and center-tapped output transformer (ZIN ≈ 5.2 Ω per device) to achieve 30 W POUT with improved harmonic suppression and reduced even-order distortion.

What heatsink interface material meets the Rth(c-s) = 0.30 °C/W specification?

Dow Corning 340 thermal compound is explicitly specified in the datasheet. Apply a 0.05 mm uniform layer between the M113 flange and flat copper/aluminum heatsink surface. Avoid silicone-free pastes or pads, as they increase Rth(c-s) beyond 0.30 °C/W and risk thermal runaway at full power.

Is SD2902 RoHS-compliant and lead-free?

No - the SD2902 is a legacy part manufactured prior to RoHS Directive 2002/95/EC. It contains lead in solder bonds and gold-plated leads. STMicroelectronics discontinued RoHS conversion; no lead-free version exists. For new designs, consider ST's newer RF power portfolio (e.g., STD12NF10L) with RoHS compliance.