STMicroelectronics SD4933

Overview

SD4933 from STMicroelectronics is an N-channel enhancement-mode RF power MOSFET designed for HF/VHF/UHF broadband amplifier stages in 50 V ISM applications up to 100 MHz. It delivers ≥300 W output power with 24 dB gain at 30 MHz, supports 20:1 all-phase load mismatch tolerance, and features 200 V drain-source breakdown voltage and 648 W power dissipation capability.

For engineers reviewing the SD4933 datasheet, SD4933 pinout, SD4933 application, or SD4933 equivalent, key selection criteria include its ruggedness under VSWR stress, thermal stability at junction temperatures up to 200 °C, gate threshold voltage sorting (2.5–3.75 V), and M177 hermetic plastic package suitability for high-power RF transmitter final stages.

Technical Context

The SD4933 operates as a single-ended Class AB or Class C RF power amplifier transistor with fixed bias (IDQ = 250 mA) and 50 V DC supply. Its dynamic performance is characterized at 30 MHz with input matching network (Zin = 1.6 – j5.0 Ω) and output impedance (Zdl = 3.3 + j1.0 Ω), enabling broadband operation across HF/VHF bands.

It employs a vertically diffused silicon MOS structure optimized for avalanche energy handling (1200 mJ) and transient thermal robustness (RthJC = 0.27 °C/W). Gate drive requires ±20 V rating compliance, and static parameters include GFS = 8–14 S and CISS = 1000 pF at VDS = 50 V, f = 1 MHz.

Key Specifications

Pinout & Package

The SD4933 is housed in the M177 epoxy-sealed plastic package with flange-mounted metal base for direct thermal coupling. The case serves as the drain connection, and the package is rated for industrial temperature operation (−65 °C to +150 °C storage).

Key Features

Applications

Equivalent & Alternatives

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

Compared with MRF1K50N and BLF188XR, the SD4933 uniquely balances 200 V ruggedness, 300 W CW output, and 20:1 VSWR tolerance specifically for 50 V HF/VHF ISM amplifiers-making it irreplaceable in fixed-frequency industrial heating and amateur radio transmitters.

Availability

SD4933 is available at Aetrix Electronics and suitable for HF/VHF transmitter final stages, industrial RF heating systems, and ISM-band communication links requiring stable component supply and long-term lifecycle continuity.

Supply support for SD4933 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, MEMS, and RF solutions for industrial, automotive, and communications markets.

The SD4933 belongs to ST's high-power RF MOSFET product line, engineered specifically for rugged, high-efficiency amplifier stages in unlicensed ISM bands up to 100 MHz-emphasizing thermal reliability, VSWR survivability, and factory-sorted parametric consistency.

FAQ

What is the maximum continuous drain current rating for SD4933?

The SD4933 has an absolute maximum drain current (ID) rating of 40 A at TCASE = 25 °C. However, in practical RF amplifier operation at 30 MHz with 50 V supply and 250 mA quiescent current, the peak drain current remains below 35 A due to Class AB conduction angle limiting. Thermal derating applies above 25 °C case temperature per the RthJC = 0.27 °C/W specification.

Does SD4933 require external gate protection diodes?

No-SD4933 incorporates internal gate protection structures compliant with IEC 61000-4-2 Level 4 (8 kV contact discharge). Its ±20 V gate-source voltage rating and 500 nA IGSS at VGS = 20 V confirm robust electrostatic immunity. External Zener clamps are unnecessary unless operating in high-noise industrial environments with long gate traces.

Can SD4933 be paralleled for higher output power?

Yes-SD4933 supports parallel operation using factory-sorted GFS/VGS bins (e.g., E6/E7 or F8/F9) to ensure current sharing within ±10%. Layout must maintain identical source inductance per device (pins 2/4/5) and use low-inductance gate drive with individual 10 Ω series resistors. Thermal coupling between devices on the same heatsink is mandatory to prevent thermal runaway.

What is the recommended PCB layout for SD4933's M177 package?

Mount the M177 flange directly to a copper-filled thermal pad (≥4 cm²) with ≥6 thermal vias (0.3 mm diameter, 0.8 mm pitch) connecting to inner ground planes. Keep gate traces short (<5 mm), shielded, and routed over solid ground. Use separate source-return paths for pins 2/4/5 to minimize common-impedance coupling. Avoid routing RF traces near gate or source nodes to prevent instability.