onsemi MJF47G

Overview

MJF47G from onsemi is an NPN silicon power transistor in a TO-220 Fullpak isolated package, rated for 250 V_CEO(sus), 1 A continuous collector current, and 28.4 W power dissipation at T_C = 25°C. It serves as a high-voltage switching element in line-operated audio output amplifiers, switching power supply drivers, and isolated-mounting applications where electrical isolation between device case and heatsink is mandatory.

For engineers reviewing the MJF47G datasheet, pinout, applications, or equivalent options, key selection criteria include its 3500 V_RMS UL-recognized isolation rating, 4.4 °C/W junction-to-case thermal resistance, and verified suitability for Class II AC-powered systems requiring reinforced insulation without external isolating washers.

Technical Context

The MJF47G is a ruggedized, electrically isolated NPN bipolar junction transistor optimized for high-voltage switching with guaranteed V_CEO(sus) = 250 V and f_T = 10 MHz. Its design integrates a fully insulated plastic package (Case 221D) that eliminates need for mica washers or silicone pads during heatsink mounting.

It operates across –65°C to +150°C junction temperature range, supports 2 A peak collector current, and delivers h_FE ≥ 30 at I_C = 0.3 A and V_CE = 10 V - enabling stable gain-controlled switching in flyback and audio driver topologies where thermal stability and isolation integrity are critical.

Key Specifications

Pinout & Package

Package: TO-220 Fullpak (Case 221D, Style 2), Pb-free, fully isolated plastic housing with metal tab electrically isolated from internal semiconductor die. Mounting 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 high-voltage isolated switching transistor applications.

Compared with TIP47 and MJF44G, the MJF47G uniquely combines 250 V_CEO(sus), 3500 V_RMS isolation, and TO-220 Fullpak packaging - making it the only option among the three qualified for reinforced insulation in 230 VAC consumer and industrial equipment without layout or BOM changes.

Availability

MJF47G is available at Aetrix Electronics and suitable for line-operated audio amplifiers, switching power supply drivers, and industrial motor control circuits requiring stable component supply with certified isolation performance.

Supply support for MJF47G 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 manufacturer specializing in energy-efficient, high-reliability power, analog, sensor, and logic solutions for automotive, industrial, and cloud infrastructure markets.

The MJF47G belongs to onsemi's high-voltage isolated power transistor product line, engineered specifically for AC-line-connected systems demanding regulatory-compliant galvanic isolation without added mechanical insulation components.

FAQ

What is the maximum mounting torque specification for the MJF47G?

The MJF47G must be mounted with a screw torque no greater than 10 in·lbs. Exceeding this value risks cracking the plastic package around the mounting hole, which degrades or destroys the 3500 V_RMS isolation capability. onsemi validates thermal performance and isolation integrity only within this torque range, as confirmed in Figures 10–13 and the Mounting Information section of the MJF47G datasheet.

Does the MJF47G require external isolation hardware when mounted to a metal heatsink?

No, the MJF47G does not require external isolation hardware. Its TO-220 Fullpak package features a fully insulated metal tab, and it is UL-recognized (File #E69369) for 3500 V_RMS isolation between leads and heatsink. This eliminates the need for mica washers, silicone pads, or other insulating materials - a key differentiator from standard TO-220 transistors like the TIP47.

What is the safe operating area (SOA) limitation for the MJF47G at 100°C case temperature?

At T_C = 100°C, the MJF47G's SOA is constrained by thermal limits rather than secondary breakdown. Per Figure 7 and Figure 8, its maximum continuous power drops to approximately 11 W (28.4 W × [1 − (100−25) × 0.227/28.4]), and the allowable I_C–V_CE envelope shifts leftward - requiring derating below 1 A if V_CE exceeds ~15 V. Designers must reference the normalized transient thermal curve (Figure 6) for pulsed operation.

How does the MJF47G compare to the MJF44G in terms of voltage rating and use cases?

The MJF47G has a 250 V_CEO(sus) rating versus the MJF44G's 150 V_CEO(sus), making the MJF47G suitable for 230 VAC line applications with transient margin, while the MJF44G is limited to 120 VAC or low-voltage DC systems. Both share identical isolation rating (3500 V_RMS), package, and thermal specs - but voltage mismatch prevents direct substitution in high-line designs.

Is the MJF47G pin-compatible with the TIP47, and can it be used as a drop-in replacement?

The MJF47G uses Style 2 pinout (Base–Collector–Emitter) and matches the TIP47's pin assignment and mechanical footprint. However, it is not a drop-in replacement due to its isolated package - which alters thermal interface behavior and eliminates need for insulating hardware. While PCB layout is compatible, system-level validation of isolation compliance and thermal performance is required before substitution.