onsemi MJF3055

Overview

MJF3055 from onsemi is an NPN silicon power transistor in a TO-220 Fullpak isolated package, rated for 90 V V_CEO(sus), 10 A continuous collector current, and 30 W power dissipation at T_C = 25°C - designed for high-reliability linear amplification and hard-switching applications in industrial power supplies and motor control circuits.

For engineers reviewing the MJF3055 datasheet, pinout, applications, or equivalent options, key selection considerations include its 4500 V_RMS isolation rating, 4.0 °C/W junction-to-case thermal resistance, guaranteed h_FE ≥ 20 at 4 A/4 V, and compatibility with standard TO-220 heatsink mounting without isolating washers.

Technical Context

The MJF3055 operates as a medium-power bipolar junction transistor optimized for robustness in thermally demanding switching and analog amplifier stages. Its isolated overmold package eliminates need for insulating hardware, and its 90 V V_CEO(sus) and 2.0 MHz f_T support stable operation in 48–72 V DC bus systems with moderate bandwidth requirements.

Electrical behavior is characterized by V_CE(sat) ≤ 1.0 V at I_C/I_B = 10, V_BE(on) ≤ 1.5 V at I_C = 4 A, and h_FE ranging from 5.0 (at 10 A) to 100 (at 0.02 A), enabling predictable bias design across load conditions from standby to full conduction.

Key Specifications

Pinout & Package

Package: TO-220 Fullpak (Case 221D-03), fully isolated overmold construction with integrated heatsink interface. Mounting screw torque must not exceed 10 in·lbs to preserve isolation integrity.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJE3055T, MJF3055 trades minor thermal advantage for critical isolation and simplified mechanical integration; versus STP16NF06L, it offers superior linearity, proven SOA for analog use, and native complementary pairing - making it preferred for linear amplifiers, regulated supplies, and safety-compliant industrial controls.

Availability

MJF3055 is available at Aetrix Electronics and suitable for industrial motor drives, audio power amplifiers, and linear voltage regulators requiring stable component supply, long-term lifecycle support, and UL-recognized isolation compliance.

Supply support for MJF3055 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power management, analog, sensor, and connectivity solutions for automotive, industrial, and cloud infrastructure markets.

The MJF3055 belongs to onsemi's Complementary Silicon Power Transistors product line, engineered for rugged, high-current linear and switching applications where isolation, reliability, and thermal performance are critical - especially in safety-regulated industrial power systems.

FAQ

What is the maximum mounting torque specification for the MJF3055?

The MJF3055 must be mounted using a 4-40 screw with torque limited to ≤10 in·lbs. Exceeding this value risks cracking the overmold package and compromising the 4500 V_RMS isolation rating. onsemi validates mechanical integrity and isolation performance only within this torque range, and recommends using a compression washer to maintain consistent pressure during thermal cycling. Always verify torque with a calibrated tool during production assembly of the MJF3055.

Does the MJF3055 require an insulating washer when mounted to a heatsink?

No, the MJF3055 does not require an insulating washer due to its fully isolated overmold package, which provides 4500 V_RMS isolation between all leads and the heatsink interface. This eliminates thermal interface layers that increase junction-to-ambient resistance. The MJF3055 is UL recognized (File #E69369) for direct mounting, and its design specifically targets reduced system cost and simplified assembly - confirmed in the official datasheet section "No Isolating Washers Required".

What is the minimum DC current gain (h_FE) of the MJF3055 at full load?

The MJF3055 guarantees h_FE ≥ 5.0 at I_C = 10 A and V_CE = 4.0 Vdc, per the Electrical Characteristics table in the onsemi datasheet. At lower currents (e.g., I_C = 4.0 A), h_FE is ≥ 20. This validated gain range allows precise base drive calculation across operating conditions - essential for stable biasing in both switching and linear amplifier implementations of the MJF3055.

Can the MJF3055 be used as a direct replacement for the MJE3055T?

The MJF3055 shares identical electrical specifications and pinout with the MJE3055T but adds 4500 V_RMS isolation and UL recognition. It is not a drop-in replacement in non-isolated designs because its thermal resistance (R_JC = 4.0 °C/W) is slightly higher than the MJE3055T's 3.0 °C/W. However, for new designs requiring isolation compliance or simplified mounting, the MJF3055 supersedes the MJE3055T - provided heatsink design accounts for the 1.0 °C/W difference. Always revalidate thermal performance when substituting the MJF3055.

What is the safe operating area (SOA) limitation for single-pulse operation of the MJF3055?

The MJF3055's forward-bias SOA (Figure 1) defines maximum simultaneous V_CE and I_C under single-pulse conditions. At 100 μs pulse width, it supports up to 30 V and 10 A; at 10 ms, limits reduce to ~15 V and 10 A due to thermal constraints. Secondary breakdown is avoided by staying left of the curve's knee - critical for inductive switching. These boundaries are measured per JEDEC standards and apply directly to the MJF3055; exceeding them risks localized hot-spot formation and permanent degradation of the device.