STMicroelectronics SD4931

Overview

SD4931 from STMicroelectronics is an N-channel RF power MOSFET designed for HF/VHF/UHF amplifier stages in 50 V DC large-signal applications up to 250 MHz. It delivers ≥150 W output power with 14.8 dB gain at 175 MHz, supports 20:1 all-phase load mismatch, and features 200 V drain-source breakdown voltage and 0.45 °C/W junction-to-case thermal resistance.

For engineers reviewing the SD4931 datasheet, SD4931 pinout, SD4931 application, or SD4931 equivalent, key selection criteria include RF power handling at 175 MHz, ruggedness under VSWR stress, thermal performance in air-cooled or heatsink-mounted RF final stages, and gate threshold sorting for bias stability in broadband amplifiers.

Technical Context

The SD4931 operates as a Class AB or Class C RF power amplifier transistor with fixed-gate-bias capability. Its 200 V V(BR)DSS rating enables operation at 50 V supply with headroom for transient overvoltage, while its 20:1 load mismatch tolerance ensures reliability in antenna-coupled or tunable matching networks.

Thermal design is enabled by low RthJC (0.45 °C/W) and high PDISS (389 W), supporting continuous-wave or pulsed RF output in M174 hermetic package. Dynamic parameters-13–14.8 dB power gain and 50–56% drain efficiency at 150 W out-are specified at 175 MHz with 250 mA quiescent drain current.

Key Specifications

Pinout & Package

The SD4931 is housed in the M174 epoxy-sealed, 4-lead, flanged ceramic-metal hermetic package with integrated heatsink mounting surface. The case serves as the drain terminal, enabling direct thermal and electrical connection to the heatsink.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MRF158 and BLF188XR, the SD4931 uniquely balances 200 V ruggedness, 150 W HF/VHF output, and 20:1 load mismatch capability in a thermally efficient M174 package-making it optimal for fixed-frequency, high-VSWR industrial and broadcast amplifiers.

Availability

SD4931 is available at Aetrix Electronics and suitable for FM broadcast transmitters, land-mobile radio base stations, RF plasma generators, and amateur radio linear amplifiers requiring stable component supply across long-lifecycle deployments.

Supply support for SD4931 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, designing and manufacturing analog, microcontroller, power, and RF components for industrial, automotive, and consumer markets.

The SD4931 belongs to ST's high-voltage RF power transistor product line, engineered specifically for rugged, high-efficiency HF/VHF/UHF amplifier stages in broadcast, communications, and industrial RF systems.

FAQ

What is the maximum recommended operating frequency for the SD4931?

The SD4931 is characterized and rated for operation up to 250 MHz, with full dynamic specifications (gain, efficiency, POUT) guaranteed at 175 MHz. While usable beyond that, gain rolls off above 200 MHz due to intrinsic capacitance and package parasitics; design validation is required for 220–250 MHz use.

Can the SD4931 be used in push-pull configuration?

Yes-the SD4931 supports push-pull operation using dual devices with complementary gate drive. Its matched source terminals (pins 2 and 4) minimize source inductance, and VGS sorting enables consistent bias current sharing. Thermal derating must account for doubled dissipation in symmetrical layouts.

Is the M174 package RoHS-compliant?

Yes-the M174 package used for SD4931 meets RoHS Directive 2011/65/EU and is part of ST's ECOPACK® program. Lead-free soldering is supported per J-STD-020, with peak reflow temperature up to 260 °C for 30 seconds, though the device is typically mounted via screw-down heatsink assembly rather than reflow.

Does ST provide application schematics for SD4931-based amplifiers?

Yes-ST document AN317 "Design of HF/VHF Power Amplifiers Using SD4931" provides complete schematic, layout guidelines, matching network values, and thermal mounting instructions for 150 W Class AB operation at 175 MHz, including PCB copper pour recommendations and gate protection networks.