NXP Semiconductors MRF1550FNT1

Overview

MRF1550FNT1 from Freescale Semiconductor is an N-channel enhancement-mode lateral RF power MOSFET designed for broadband common-source amplifier applications in 12.5 V mobile FM equipment. It delivers 50 W output power at 175 MHz, achieves 14.5 dB power gain and 55% drain efficiency, and is rated for 200°C junction temperature in a TO-272-6 plastic package.

For engineers reviewing the MRF1550FNT1 datasheet, MRF1550FNT1 pinout, MRF1550FNT1 application, or MRF1550FNT1 equivalent, key selection criteria include its 175 MHz full-power bandwidth (135–175 MHz), capability to withstand 20:1 VSWR at 15.6 Vdc with 2 dB overdrive, and thermal resistance of 0.75°C/W from junction to case - critical for high-reliability VHF/UHF power amplifier designs.

Technical Context

This device operates as a common-source RF power amplifier with fixed 12.5 V drain supply and 500 mA quiescent bias current (IDQ). Its lateral MOSFET architecture provides inherent immunity to thermal runaway and stable large-signal performance across 135–175 MHz without requiring complex bias compensation networks.

It features characterized series-equivalent large-signal impedances (e.g., Zin = 3.7 + j2.3 Ω and ZOL* = 0.7 + j1.1 Ω at 175 MHz) and exhibits high gain (S21 = 1.349 @ 150 MHz, 0.892 @ 200 MHz) with low reverse isolation (|S12| ≤ 0.01), enabling robust broadband matching using passive LC networks per Freescale's reference test circuit.

Key Specifications

Pinout & Package

Package: TO-272-6 WRAP PLASTIC (Case 1264-10, Style 1), surface-mount with integrated heatsink tab. Requires bolt-down or clamping mechanical attachment per AN3263/AN3789 for reliable thermal conduction.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MRF1550NT1, the MRF1550FNT1 offers identical RF performance but superior manufacturability and thermal interface via its WRAP package; versus MRFE6VP61K25H, it provides optimized 50 W mobile-band operation with simpler biasing and lower system-level integration effort.

Availability

MRF1550FNT1 is available at Aetrix Electronics and suitable for land mobile radio transmitters, FM broadcast auxiliary links, public safety repeaters, and amateur radio amplifiers requiring stable component supply and long-term production continuity.

Supply support for MRF1550FNT1 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

Freescale Semiconductor (now part of NXP Semiconductors) is a global leader in RF power solutions, specializing in high-efficiency, rugged transistors for wireless infrastructure and mobile communications.

The MRF1550FNT1 belongs to Freescale's lateral N-channel RF power MOSFET product line, engineered specifically for broadband VHF/UHF mobile FM equipment operating at 12.5 V with stringent reliability and thermal demands.

FAQ

What is the maximum operating frequency for full-power operation of the MRF1550FNT1?

The MRF1550FNT1 is specified for full 50 W output power across 135–175 MHz. While S-parameters extend to 600 MHz, gain and efficiency degrade significantly above 175 MHz; Freescale's characterization and application guidance confirm 175 MHz as the upper limit for rated full-power operation.

Does the MRF1550FNT1 require external gate protection, and why?

Yes, the MRF1550FNT1 requires external gate protection because it lacks an internal monolithic zener diode. Its gate oxide is susceptible to ESD damage and transient overvoltage coupled from the drain via Crss; Freescale explicitly recommends an external zener diode and low-impedance gate termination to prevent unintended turn-on or permanent gate oxide rupture.

How does the MRF1550FNT1's thermal resistance impact heatsink design?

The MRF1550FNT1 has a junction-to-case thermal resistance of 0.75°C/W. To maintain TJ ≤ 200°C at 165 W dissipation (PD max), the heatsink must limit case-to-ambient rise to ≤ 41.7°C - requiring a low-thermal-resistance mechanical interface (e.g., clamping per AN3789) and heatsink thermal resistance ≤ 0.25°C/W, including interface material losses.

Can the MRF1550FNT1 be used in Class C amplifier configurations?

No - the MRF1550FNT1 is characterized and optimized for Class AB operation at IDQ = 500 mA. Its lateral MOSFET structure and published large-signal impedances assume linear biasing; Class C operation would violate the specified DC bias conditions, risk thermal instability, and invalidate the provided Zin/ZOL* data and efficiency metrics.

What is the significance of the "F" in MRF1550FNT1?

The "F" in MRF1550FNT1 denotes the TO-272-6 WRAP plastic package (Case 1264-10), distinguishing it from the standard TO-272-6 variant (MRF1550NT1, Case 1264A-03). The WRAP construction enhances thermal interface uniformity and supports fully automated SMT placement, while maintaining identical electrical and thermal specifications.