STMicroelectronics STAC2942BW

Overview

STAC2942BW from STMicroelectronics is a gold-metallized N-channel MOSFET RF power transistor in common-source push-pull configuration, designed for HF/VHF/UHF amplifier stages in 50 V DC systems. It delivers 350 W minimum output power at 175 MHz with 21 dB gain and 60% drain efficiency, operating up to 250 MHz with 130 V V(BR)DSS rating and 200 °C maximum junction temperature.

For engineers reviewing the STAC2942BW datasheet, STAC2942BW pinout, STAC2942BW application, or STAC2942BW equivalent, key selection criteria include its 175 MHz large-signal performance, STAC780-4B air-cavity package thermal resistance (0.28 °C/W), gate-source leakage (<250 nA), and safe operating area validated for 10 ms pulse and DC operation.

Technical Context

This device operates as a balanced push-pull RF power amplifier stage with gate-to-gate and drain-to-drain impedance matching-ZIN = 2.0 − j2.0 Ω and ZDL = 3.5 + j5.2 Ω at 175 MHz. Its static characteristics include VGS(Q) = 1.5–4.0 V at ID = 250 mA and GFS = 5 S, enabling precise bias control in Class AB or C configurations.

Dynamic operation is specified under 50 V supply, 2 × 250 mA quiescent current, and 4 W input drive, yielding 350–450 W output power and 60–75% drain efficiency. The device supports 5:1 VSWR load mismatch tolerance across all phase angles at full rated output, critical for broadcast and industrial RF amplifiers.

Key Specifications

Pinout & Package

The STAC2942BW is housed in the STAC780-4B air-cavity ceramic-metal package, featuring bottom-side source connection for optimal thermal path to heatsink and gold metallization for corrosion resistance and wire-bond reliability.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MRF1K50N and PD85003, STAC2942BW offers optimal balance of 350 W output, 50 V operation, 0.28 °C/W thermal resistance, and 175 MHz-optimized impedance-making it ideal for fixed-frequency HF/VHF broadcast and industrial RF systems requiring proven reliability and thermal headroom.

Availability

STAC2942BW is available at Aetrix Electronics and suitable for FM broadcast transmitters, UHF TV driver stages, industrial RF heating generators, and aerospace HF communication amplifiers requiring stable component supply and long-lifecycle support.

Supply support for STAC2942BW 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 STAC series targets high-reliability RF power applications, with STAC2942BW specifically engineered for HF/VHF amplification where thermal stability, hermetic packaging, and push-pull linearity are critical design requirements.

FAQ

What is the maximum continuous drain current for STAC2942BW?

The absolute maximum continuous drain current is 40 A at TCASE = 25 °C, but practical large-signal operation limits ID to ~2 × 250 mA quiescent per side. Peak pulsed current capability reaches 1000 A in the safe operating area (SOA) for 1 ms pulses, validated in Figure 9 of DS6158 Rev 8.

Does STAC2942BW require external gate resistors for stability?

Yes-ST's recommended test circuit (Figure 12) uses 430 Ω gate termination resistors (R1, R2) to dampen parasitic oscillations. Without them, the device exhibits instability above 100 MHz due to CRSS = 12 pF and high GFS = 5 S; layout-dependent ringing may occur in uncontrolled PCB environments.

Can STAC2942BW be operated at 28 V instead of 50 V?

No-it is optimized for 50 V operation; at 28 V, POUT drops below 150 W and efficiency falls below 45%, per Figure 3 and Figure 5. The 130 V V(BR)DSS rating does not imply low-voltage suitability; gate threshold (VGS(Q) = 1.5–4.0 V) and transconductance profile are calibrated for 50 V class-AB biasing.

Is the STAC780-4B package compatible with standard TO-247 heatsinks?

No-the STAC780-4B is a custom air-cavity ceramic-metal package (34.19 mm × 18.08 mm × 5.33 mm) with bottom-side source thermal pad; it requires dedicated mounting hardware and thermal interface material. Standard TO-247 clips or insulators do not align with its pin geometry or mechanical tolerances per Table 8.