onsemi MJD117

Overview

MJD117 from ON Semiconductor is an NPN silicon Darlington transistor designed for medium-power switching applications, featuring a 100 V collector-emitter sustaining voltage (V_CEO(sus)), 2 A DC collector current (I_C), and built-in emitter-collector damper diode. It operates with high DC current gain (h_FE = 500–12,000 at I_C = 0.5–4 A) and is commonly used in relay drivers, lamp dimmers, and motor control circuits where high current amplification and low base drive are required.

For engineers reviewing the MJD117 datasheet, pinout, applications, or equivalent options, key selection considerations include its D-PAK package thermal performance, V_CE(sat) of 2–3 V at I_C = 2–4 A, integrated damper diode eliminating external snubbing, and suitability for surface-mount industrial switching designs requiring robust SOA and 150 °C junction temperature capability.

Technical Context

The MJD117 employs a monolithic Darlington pair architecture with internal base-emitter resistors and a damper diode connected between emitter and collector. Its high h_FE enables direct drive from microcontrollers or logic gates without additional pre-driver stages.

It supports pulsed operation up to 4 A (I_CP) with 2% duty cycle and exhibits f_T = 25 MHz at V_CE = 10 V, I_C = 0.75 A - sufficient for moderate-speed switching but not RF or high-frequency PWM applications. Safe Operating Area (SOA) is defined up to 100 V and 2 A in DC mode, derating linearly above T_C = 25 °C per the published power derating curve.

Key Specifications

Pinout & Package

D-PAK (TO-252) surface-mount package with exposed drain pad for thermal enhancement; lead-formed for PCB mounting without bending.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD122 and TIP122, the MJD117 offers optimal balance of surface-mount compatibility, integrated protection, and 100 V/2 A capability for cost-sensitive industrial controls - whereas MJD122 trades higher voltage margin for slightly reduced gain spread, and TIP122 sacrifices board area and design simplicity for legacy package familiarity.

Availability

MJD117 is available at Aetrix Electronics and suitable for relay driver circuits, lamp dimming controls, motor speed controllers, and industrial solenoid drivers requiring stable component supply, long-lifecycle support, and consistent parametric performance across production batches.

Supply support for MJD117 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 is a global semiconductor manufacturer specializing in power management, analog, sensor, and discrete solutions for automotive, industrial, and cloud power applications.

The MJD117 belongs to ON Semiconductor's legacy Fairchild discrete transistor portfolio, engineered specifically for ruggedized medium-power switching in industrial control, appliance, and building automation systems where reliability, thermal robustness, and integration are critical.

FAQ

What is the maximum continuous collector current rating for the MJD117?

The MJD117 has a DC collector current rating (I_C) of 2 A at T_C = 25 °C. This value assumes proper heatsinking and derates linearly as case temperature increases - for example, to approximately 1.2 A at T_C = 100 °C per the published power derating curve. The MJD117 must not be operated beyond this limit in continuous conduction mode without thermal analysis confirming safe junction temperature.

Does the MJD117 include a built-in damper diode, and how is it connected?

Yes, the MJD117 integrates a damper diode between emitter and collector terminals, with cathode at emitter and anode at collector. This configuration provides automatic flyback voltage clamping during inductive load turn-off, eliminating the need for an external diode. The diode is monolithically fabricated within the same die as the Darlington pair and shares the same thermal environment as the transistor junction.

What package type does the MJD117 use, and what are its thermal characteristics?

The MJD117 uses the D-PAK (TO-252) surface-mount package with an exposed collector pad for enhanced thermal conduction. Its maximum collector dissipation is 20 W at T_C = 25 °C, dropping to 1.75 W at T_A = 25 °C (free-air). Thermal resistance from junction to case (R_θJC) is approximately 1.25 °C/W, making it suitable for compact heatsinked or thermally optimized PCB layouts in industrial applications.

How does the DC current gain (h_FE) of the MJD117 vary with operating conditions?

The MJD117 specifies h_FE ranging from 500 (min) at I_C = 0.5 A to 12,000 (max) at I_C = 4 A, measured at V_CE = 3 V. Gain decreases significantly below I_C = 0.1 A and above I_C = 4 A. Designers should verify actual h_FE at their target operating point using the typical curves in the datasheet, as variation across lots and temperature affects base drive requirements for reliable saturation.

Can the MJD117 replace the MJD112 in existing designs?

Yes, the MJD117 is a direct functional replacement for the MJD112, sharing identical D-PAK package, pinout, absolute maximum ratings, and electrical characteristics - including V_CEO(sus) = 100 V, I_C = 2 A, and integrated damper diode. Both devices originate from the same Fairchild family and were consolidated under ON Semiconductor's unified part numbering after acquisition; no PCB or schematic changes are required for migration.