onsemi MJE5742

Overview

MJE5742 from onsemi is an NPN silicon power Darlington transistor designed for high-voltage inductive switching applications, featuring 400 V_CEO(sus), 8 A continuous collector current, 100 W total device dissipation at T_C = 25°C, and TO-220AB package with 4-pin configuration (dual collector). It is used in motor controls and solenoid drivers where robust clamped inductive turn-off capability is required.

For engineers reviewing the MJE5742 datasheet, pinout, applications, or equivalent options, key selection criteria include V_CEO(sus) rating, second breakdown SOA, R_JC thermal resistance, integrated collector-emitter diode functionality, and base drive requirements for reliable switching in 250–400 V inductive loads.

Technical Context

The MJE5742 operates as a monolithic Darlington pair with internal base-emitter resistor network optimized for high-gain switching. Its clamped inductive SOA (RBSOA) is validated under reverse-biased base conditions with V_BE(off) ≤ 5 V, supporting safe turn-off at up to 250 V_CE(pk) and 6 A_IC(pk).

It integrates a built-in collector-to-emitter diode with V_f = 2.5 V at I_F = 5 A, eliminating external flyback diodes in relay and solenoid driver circuits. Switching performance includes t_s = 8 µs storage time and t_f = 2 µs fall time under resistive load conditions (V_CC = 250 V, I_C(pk) = 6 A).

Key Specifications

Pinout & Package

Package: TO-220AB (Case 221A-09), 4-pin variant (Style 1), with metal tab electrically connected to collector. Pin 1 = Base, Pin 2 = Collector, Pin 3 = Emitter, Pin 4 = Collector (dual collector configuration).

Key Features

Applications

Equivalent & Alternatives

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

Compared with BDW84C and TIP142, the MJE5742 uniquely supports 400 V sustained switching with validated RBSOA and integrated diode-making it the only option among the three qualified for 250–400 V inductive turn-off without external protection components.

Availability

MJE5742 is available at Aetrix Electronics and suitable for motor controls, solenoid drivers, and switching regulators requiring stable component supply in industrial automation, HVAC equipment, and power tool designs.

Supply support for MJE5742 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 is a global semiconductor supplier delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The MJE5742 belongs to onsemi's legacy power bipolar transistor product line, engineered specifically for ruggedized high-voltage inductive switching in cost-sensitive industrial power electronics.

FAQ

What is the maximum continuous collector current rating for the MJE5742?

The MJE5742 has a maximum continuous collector current (I_C) rating of 8 A at T_A = 25°C. This value decreases with rising ambient or case temperature per its 0.016 W/°C derating factor above 25°C. For sustained operation, thermal design must ensure junction temperature remains within −65°C to +150°C limits. The MJE5742 achieves this with R_JC = 1.25 °C/W and 100 W dissipation capability at T_C = 25°C.

Does the MJE5742 include an integrated clamp diode, and what is its forward voltage?

Yes, the MJE5742 integrates a collector-to-emitter diode optimized for clamping inductive flyback energy. Its forward voltage (V_f) is specified at 2.5 Vdc when conducting 5 A, matching typical fast recovery rectifiers. This eliminates the need for an external diode in solenoid, relay, and motor control applications-reducing component count and PCB footprint. The MJE5742 datasheet confirms this diode is part of the monolithic Darlington structure and functions reliably under clamped inductive switching conditions.

What is the safe operating area (SOA) classification for the MJE5742 during reverse-biased turn-off?

The MJE5742 is characterized for Reverse Bias Safe Operating Area (RBSOA) under clamped inductive conditions with V_BE(off) ≤ 5 V. Its RBSOA supports up to 250 V_CE(pk) and 6 A_IC(pk) in single-pulse mode, as shown in Figure 7 of the official datasheet. This rating is verified without avalanche stress, ensuring reliability in high-voltage turn-off events. The MJE5742's RBSOA differs from forward-bias SOA by requiring reverse base bias and is distinct from the MJE5740's lower 200 V_CE(pk) limit.

How does the MJE5742 pinout differ from standard TO-220 NPN transistors?

The MJE5742 uses TO-220AB Style 1 pinout: Pin 1 = Base, Pin 2 = Collector, Pin 3 = Emitter, Pin 4 = Collector (dual collector). Unlike standard 3-pin TO-220 transistors, the fourth pin duplicates the collector connection to reduce current density and improve thermal conduction through the metal tab. This configuration is explicitly defined in the "MECHANICAL CASE OUTLINE" section of the MJE5742 datasheet and must be accounted for in PCB layout and heatsink mounting to avoid misconnection or thermal bottlenecks.

Is the MJE5742 still in active production, and what is its lifecycle status?

The MJE5742 is marked as discontinued in onsemi's official ordering information (Note 4, page 6 of datasheet Rev. 13), with the note: "This device is not recommended for new design." However, Aetrix Electronics maintains active inventory and supply chain support for legacy production programs. For new designs, engineers should consult onsemi for approved replacements, while existing MJE5742-based systems can rely on Aetrix's continuity management and traceable sourcing. The MJE5742 remains fully functional and specification-compliant per its published datasheet.