STMicroelectronics SD56120M

Overview

SD56120M from STMicroelectronics is a common-source N-channel enhancement-mode lateral MOSFET RF power transistor designed for broadband TV broadcast amplifiers up to 1.0 GHz. It delivers 120 W output power with 13 dB gain at 860 MHz and 32 V supply, features internal input matching, BeO-free M252 ceramic package, and operates in push-pull configuration.

For engineers reviewing the SD56120M datasheet, SD56120M pinout, SD56120M application, or SD56120M equivalent, key selection criteria include thermal resistance (0.55 °C/W), drain-source breakdown voltage (65 V), gate-source voltage range (±20 V), output power linearity under 10:1 VSWR, and impedance matching at 860 MHz (Z_IN = 5.57 + j3.488 Ω).

Technical Context

The SD56120M employs lateral DMOS architecture optimized for high-efficiency RF power amplification in UHF band. Its dual-drain/dual-gate structure supports balanced push-pull operation, while internal input matching eliminates external tuning components at 860 MHz.

Thermal design is enabled by low junction-to-case resistance (0.55 °C/W) and ceramic-metal M252 package rated for 236 W dissipation at T_CASE = 70°C. Dynamic performance is characterized at 32 V, 400 mA quiescent drain current, with 50% drain efficiency and 10:1 load mismatch tolerance.

Key Specifications

Pinout & Package

The SD56120M uses the M252 (.400 × .860 inch, 4-lead, balanced, hermetic with flange) ceramic-metal package with integral copper flange for direct heatsink mounting and hermetic sealing. Package complies with ECOPACK® lead-free interconnect standards.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MRF158 and BLF8G22LS-150, the SD56120M offers optimal trade-off of integrated matching, thermal efficiency, and UHF broadcast-specific linearity-making it uniquely suited for fixed-frequency, high-reliability TV transmitter finals where board space and thermal management are constrained.

Availability

SD56120M is available at Aetrix Electronics and suitable for UHF broadcast transmitters, CATV headend amplifiers, wireless infrastructure PAs, and industrial RF heating systems requiring stable component supply across long production lifecycles.

Supply support for SD56120M 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 SD56120M belongs to ST's LDMOST plastic family of RF power transistors, engineered specifically for high-linearity, high-efficiency broadband amplification in commercial broadcast and infrastructure applications up to 1 GHz.

FAQ

What is the recommended gate bias voltage for linear operation?

The SD56120M achieves optimal linearity and gain at V_GS(Q) = 2.0–5.0 V (typical 3.5 V) with 400 mA quiescent drain current per channel. Bias must be applied independently to pins 4 and 5 using matched resistive dividers to maintain symmetry; deviation beyond ±0.1 V between gates increases IMD3 by >6 dB.

Can SD56120M be operated in Class C for ISM heating?

Yes-the device supports Class C operation with peak drain current up to 14 A and 200°C junction temperature. For ISM heating at 860 MHz, use V_DD = 32 V, gate drive amplitude ≥ 8 Vpp, and ensure case temperature remains ≤ 70°C via flange-mounted heatsink with thermal interface material (TIM) having <0.1 °C·in²/W resistance.

Is external input matching required despite internal matching?

No external input matching is required at 860 MHz-the internal network provides Z_IN = 5.57 + j3.488 Ω, which transforms to 50 Ω with <0.2 dB insertion loss. However, broadband operation below 700 MHz or above 950 MHz requires external tuning using the test circuit's C3/C4 variable capacitors per Figure 6.

What is the maximum allowable VSWR at the output port?

The SD56120M is qualified for continuous operation under 10:1 VSWR at all phase angles when delivering 120 W P_OUT at 860 MHz and 32 V supply. This is verified per Table 4 (h_D) and enables direct connection to antennas without isolators in broadcast applications where VSWR excursions are expected.