onsemi MJD112T4

Overview

MJD112T4 from ON Semiconductor is an NPN silicon Darlington transistor in D-PAK package, rated for 100 V V_CEO, 2 A DC collector current, and 20 W collector dissipation at T_C = 25°C. It integrates a built-in damper diode between emitter and collector and delivers high DC current gain (h_FE = 500–12,000 at I_C = 0.5–4 A), making it suitable for medium-power switching in motor drivers and relay drivers.

For engineers reviewing the MJD112T4 datasheet, pinout, applications, or equivalent options, key selection considerations include its Darlington configuration with integrated clamp diode, V_CE(sat) ≤ 3 V at I_C = 4 A / I_B = 40 mA, thermal derating above 25°C case temperature, and D-PAK surface-mount compatibility for high-current PCB layouts.

Technical Context

The MJD112T4 implements a monolithic NPN Darlington pair with internal base-emitter resistor network (R1 ≈ 10 kΩ, R2 ≈ 0.6 kΩ) and an integrated emitter-to-collector damper diode. Its structure enables high current amplification while reducing external biasing complexity.

It operates with V_BE(on) = 2.8 V at I_C = 2 A, exhibits f_T = 25 MHz at V_CE = 10 V / I_C = 0.75 A, and maintains safe operation up to T_J = 150°C with junction-to-case thermal resistance optimized for D-PAK mounting on copper pads.

Key Specifications

Pinout & Package

D-PAK (TO-252) surface-mount package with exposed drain pad for thermal conduction; lead-formed for gull-wing soldering. Pin assignment verified per Fairchild MJD112 Rev. B datasheet and ON Semiconductor mechanical drawings.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BD679A and MJD122T4, the MJD112T4 uniquely combines integrated damper diode functionality with D-PAK surface-mount packaging and broad h_FE range-offering layout simplification and thermal advantage over through-hole alternatives, while providing lower minimum gain than MJD122T4 for cost-sensitive volume applications.

Availability

MJD112T4 is available at Aetrix Electronics and suitable for industrial motor control, PLC output stages, and linear regulator designs requiring stable component supply, long-term lifecycle support, and RoHS-compliant D-PAK transistors.

Supply support for MJD112T4 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

ON Semiconductor (formerly Fairchild Semiconductor) is a global supplier of energy-efficient semiconductor components, specializing in power management, analog, sensors, and discrete devices.

The MJD112T4 belongs to ON Semiconductor's legacy high-voltage Darlington transistor family, designed specifically for robust medium-power switching in industrial controls, appliance motor drives, and power supply regulation where simplicity, reliability, and integrated protection are critical.

FAQ

What is the maximum continuous collector current for the MJD112T4?

The MJD112T4 is rated for 2 A DC collector current (I_C) at T_C = 25°C. Operation above this value requires derating based on case temperature per the power derating curve in the datasheet. At T_C = 100°C, the usable I_C drops to approximately 1.2 A to maintain safe junction temperature.

Does the MJD112T4 include an integrated damper diode, and how is it connected?

Yes, the MJD112T4 includes a built-in damper diode connected between emitter and collector, with cathode at collector and anode at emitter. This configuration clamps inductive flyback voltage during turn-off, protecting the transistor without requiring an external diode in relay or solenoid driver applications.

What is the typical V_CE(sat) of the MJD112T4 under full-load conditions?

The MJD112T4 specifies V_CE(sat) ≤ 3 V at I_C = 4 A and I_B = 40 mA. Under typical 2 A DC load conditions with 8 mA base drive, V_CE(sat) measures ~2 V, enabling efficient operation in linear and switching modes with predictable conduction loss.

Can the MJD112T4 be used in linear regulator applications?

Yes, the MJD112T4 is suitable for linear regulator pass elements due to its 20 W collector dissipation rating at T_C = 25°C and 150°C maximum junction temperature. When mounted on a 2 oz copper pad with thermal vias, it supports up to ~1.5 A at 10 V dropout with acceptable thermal rise.

What package type does the MJD112T4 use, and what are its key mechanical features?

The MJD112T4 uses the D-PAK (TO-252) surface-mount package with three gull-wing leads and an exposed collector pad. Key features include 6.6 mm × 9.5 mm footprint, 2.3 mm height, and thermal pad optimized for solder attachment to PCB copper areas-enabling effective heat transfer in high-current applications.