STMicroelectronics STAC3932B

Overview

STAC3932B from STMicroelectronics is an N-channel MOSFET RF power transistor in common-source push-pull configuration, rated for 100 V DC operation up to 250 MHz, delivering 580 W CW output power at 123 MHz with 24.6 dB gain and 70% drain efficiency - deployed in HF/VHF/UHF broadcast amplifiers and industrial RF heating systems.

For engineers reviewing the STAC3932B datasheet, STAC3932B pinout, STAC3932B application, or STAC3932B equivalent, key selection criteria include its 250 V V(BR)DSS rating, 0.28 °C/W junction-to-case thermal resistance, STAC780-4B air-cavity package, balanced impedance matching (ZIN = 0.8 − j3.45 Ω at 123 MHz CW), and compliance with EU RoHS directive 2002/95/EC.

Technical Context

This device operates in Class AB or Class C RF amplifier stages with dual-gate, dual-drain layout enabling balanced push-pull operation. Its static parameters include VTH = 2.0–4.0 V, GFS = 3.0–5.0 S, and CISS = 492 pF at 100 V VDS - critical for broadband impedance transformation and gate drive stability.

Dynamic performance is characterized at 123 MHz under 100 V supply and 2 × 250 mA quiescent current: POUT = 580 W (CW), ŋD = 70%, and gain flatness maintained across pulse (PW = 1 ms, DC = 10%) and continuous-wave modes - supporting high-reliability RF power generation in fixed-frequency transmitters.

Key Specifications

Pinout & Package

The STAC3932B is housed in the STAC780-4B air-cavity ceramic-metal package, featuring a bottom-side source thermal pad and isolated gate/drain terminals optimized for RF grounding and thermal management in high-power amplifier modules.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MRF300BN and BLF278, the STAC3932B delivers the highest CW output power (580 W) and efficiency (70%) at 123 MHz in the STAC780-4B package, making it the preferred choice for new HF/VHF broadcast and industrial RF designs where thermal density and gain flatness are critical.

Availability

STAC3932B is available at Aetrix Electronics and suitable for broadcast transmitters, industrial RF heating systems, avionics HF amplifiers, and scientific plasma generators requiring stable component supply and long-term lifecycle support.

Supply support for STAC3932B 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-power RF applications demanding rugged packaging, thermal stability, and broadband performance - specifically engineered for HF/VHF/UHF transmitters and industrial RF energy systems.

FAQ

What is the recommended gate drive voltage range for STAC3932B?

The STAC3932B specifies ±20 V maximum gate-source voltage (VGS), with typical gate threshold voltage (VTH) between 2.0 V and 4.0 V. For reliable Class AB operation at 123 MHz, a nominal VGS of +10 V is used with 2 × 250 mA quiescent current; gate drive must include series resistance (e.g., 10–22 Ω) to dampen parasitic oscillations.

Can STAC3932B be operated in pulsed mode, and what are the limits?

Yes - STAC3932B delivers 900 W pulsed output at 123 MHz with 1 ms pulse width and 10% duty cycle. Safe operation requires adherence to the SOA curve: peak drain current must stay below 20 A, and VDD must not exceed 100 V. Thermal cycling must respect transient impedance limits shown in Figure 4 of DS6157.

How does the STAC780-4B package improve thermal performance over standard TO-247?

The STAC780-4B uses an air-cavity ceramic-metal construction with direct bottom-side source thermal pad attachment, achieving 0.28 °C/W junction-to-case resistance - 45% lower than typical TO-247 packages (~0.51 °C/W). This enables higher sustained power density and reduces heatsink mass by ~30% in forced-air-cooled RF amplifiers.

Is STAC3932B suitable for broadband amplifier designs beyond 123 MHz?

While rated up to 250 MHz, STAC3932B's gain and efficiency drop significantly above 150 MHz: gain falls to ~20 dB and efficiency to ~60% at 200 MHz. It is optimized for narrowband operation at 123 MHz; for broadband use, impedance matching networks must be re-tuned per frequency, and SOA derating applies above 150 MHz.