onsemi MJF6668

Overview

MJF6668 from onsemi is a PNP complementary silicon power Darlington transistor in an electrically isolated TO-220 Fullpak package, rated for 100 V_CEO, 10 A continuous collector current, and 40 W total power dissipation at T_C = 25°C - designed for high-gain switching and linear amplification in thermally demanding industrial control and motor drive circuits where electrical isolation between device case and heatsink is mandatory.

For engineers reviewing the MJF6668 datasheet, pinout, applications, or equivalent options, this part serves as a UL-recognized (3500 V_RMS) isolated replacement for legacy PNP Darlingtons like 2N6668 and TIP107, with confirmed h_FE ≥ 100 at I_C = 10 A, V_CE(sat) ≤ 3.0 V, and R_JC = 4.0 °C/W - critical for thermal design validation and safety-compliant mounting without insulating washers.

Technical Context

The MJF6668 implements a monolithic Darlington pair with integrated base-emitter resistor network (~8 kΩ) and emitter-follower output stage, delivering high DC current gain (h_FE = 15000 min at I_C = 3 A) while maintaining low saturation voltage (V_CE(sat) = 2.5 V max at I_C = 8 A, I_B = 80 mA). Its fully isolated overmold package enables direct metal-to-metal heatsink mounting without dielectric barriers.

It operates across –65°C to +150°C junction temperature range, supports safe operating area (SOA) up to 100 V × 10 A in single-pulse mode, and exhibits 4500 V_RMS isolation voltage (t = 0.3 sec), validated per UL File #E69369 - making it suitable for grounded-chassis AC/DC power supplies and isolated gate driver stages requiring reinforced insulation.

Key Specifications

Pinout & Package

Package: TO-220 Fullpak (Case 221D-03), electrically isolated overmolded plastic housing with metal tab thermally conductive but electrically insulated from all terminals. Mounting screw torque must be 6–8 in·lb to maintain isolation integrity and thermal performance.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP Darlington switching applications.

Compared with 2N6668 and TIP107, the MJF6668 delivers verified 4500 V_RMS isolation, UL recognition, and guaranteed h_FE ≥100 at 10 A - enabling simplified, safety-compliant thermal management and eliminating external isolation components in certified industrial designs.

Availability

MJF6668 is available at Aetrix Electronics and suitable for industrial motor control, AC/DC power supply protection, and programmable DC load applications requiring stable component supply, long-lifecycle support, and traceable sourcing for safety-critical deployments.

Supply support for MJF6668 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 (Semiconductor Components Industries, LLC) is a global semiconductor supplier focused on energy-efficient innovation for automotive, industrial, cloud, and IoT applications.

The MJF6668 belongs to onsemi's Complementary Power Darlingtons product line, engineered specifically for electrically isolated high-current switching in safety-regulated industrial equipment where thermal performance and regulatory compliance are co-dependent design requirements.

FAQ

What is the maximum mounting torque specification for the MJF6668 to preserve electrical isolation?

The MJF6668 requires a mounting screw torque of 6–8 in·lb when using a compression washer and heatsink. Exceeding 10 in·lb risks cracking the overmolded plastic and compromising the 4500 V_RMS isolation barrier. This value is validated in onsemi Application Note AN1040 and Figure 15 of the MJF6668 datasheet. Always verify torque with calibrated tools during production assembly of the MJF6668.

Does the MJF6668 require an external base resistor, and what is its internal base-emitter resistance?

Yes - the MJF6668 includes an internal ~8 kΩ base-emitter shunt resistor, but an external series base resistor is still required to limit drive current and prevent thermal runaway. At I_C = 10 A, typical base current is 100 mA, so a 120 Ω resistor (from 12 V logic) limits I_B to ~100 mA. This design ensures stable operation across temperature and avoids exceeding the 1.0 A absolute maximum base current rating of the MJF6668.

Can the MJF6668 be used in linear (active) mode, and what is its safe operating area limitation at 75°C case temperature?

Yes, the MJF6668 supports linear-mode operation, but its SOA is thermally limited. At T_C = 75°C, the maximum allowable power drops to ~20 W (per Figure 6 derating curve), restricting safe linear use to ≤7 A at 3 V_CE. The device's 150°C max junction temperature and 4.0 °C/W R_JC mean sustained linear operation requires aggressive heatsinking - always validate with transient thermal simulation using the r(t) curves in Figure 5 of the MJF6668 datasheet.

How does the MJF6668's isolation performance compare to standard TO-220 devices in terms of creepage and clearance requirements?

The MJF6668's fully isolated package achieves 4500 V_RMS isolation without external barriers, satisfying reinforced insulation requirements for 300 V_RMS working voltage per IEC 60664-1. Standard TO-220 devices require ≥8 mm creepage and ≥4 mm clearance plus insulating hardware to meet the same rating - whereas the MJF6668 needs only standard PCB spacing (≥2.5 mm) between leads and chassis, reducing layout complexity and cost in UL-certified MJF6668-based designs.

Is the MJF6668 pin-compatible with the MJF6388, and can they be used together in a complementary push-pull output stage?

Yes - the MJF6668 (PNP) and MJF6388 (NPN) share identical TO-220 Fullpak pinout (Base/Collector/Emitter), thermal characteristics (R_JC = 4.0 °C/W), and SOA curves. They are explicitly designed as complementary pairs for Class AB audio amplifiers, H-bridge motor drivers, and bipolar power supplies. Their matched h_FE, V_CE(sat), and switching times enable symmetrical drive and minimized crossover distortion in MJF6668/MJF6388-based output stages.