onsemi MJD128T4

Overview

MJD128T4 from onsemi is a PNP complementary Darlington power transistor in DPAK (Case 369C) surface-mount package, rated for 120 V_CEO, 8 A continuous collector current, and 20 W total power dissipation at T_C = 25°C. It delivers high DC current gain (h_FE = 2500 typ. @ I_C = 4 A), built-in base-emitter shunt resistors, and is designed for general-purpose amplification and low-speed switching in industrial power supplies and motor controls.

For engineers reviewing the MJD128T4 datasheet, pinout, applications, or equivalent options, key selection considerations include its PNP Darlington topology, 120 V blocking capability, thermal resistance R_JC = 6.25 °C/W, ESD robustness (HBM Class 3B, 8 kV), and surface-mount DPAK footprint compatibility with automated assembly.

Technical Context

The MJD128T4 integrates two PNP transistors monolithically to form a Darlington pair with internal base-emitter shunt resistors, enabling simplified biasing and stable turn-off behavior. Its structure supports high-current drive with low base drive requirements-e.g., I_B = 80 mA suffices for I_C = 8 A saturation.

Thermal performance is defined by junction-to-case (R_JC = 6.25 °C/W) and junction-to-ambient (R_JA = 71.4 °C/W) resistances under specified PCB pad conditions. Safe operating area (SOA) curves account for second-breakdown limits and thermal constraints across pulse widths from 10 µs to DC at T_J(pk) ≤ 150°C.

Key Specifications

Pinout & Package

DPAK (Case 369C) surface-mount package with 4 terminals: three functional leads (Base, Collector, Emitter) plus an exposed collector tab (Pin 4) for enhanced thermal conduction and mechanical anchoring. Requires minimum pad layout per datasheet Figure 11 for rated R_JA.

Key Features

Applications

Equivalent & Alternatives

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

Compared with BDW93C, the MJD128T4 offers superior voltage margin and integrated turn-off assistance; versus MJD112T4, it provides essential PNP polarity for high-side switching and emitter-follower regulation where NPN cannot substitute directly.

Availability

MJD128T4 is available at Aetrix Electronics and suitable for industrial power supplies, DC motor control modules, relay replacement circuits, and linear amplifier stages requiring stable component supply, long-term manufacturability, and surface-mount compatibility.

Supply support for MJD128T4 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 supplier focused on energy-efficient electronics, with leadership in power management, analog, sensors, and discrete devices.

The MJD128T4 belongs to onsemi's high-voltage PNP Darlington transistor family, engineered for rugged industrial switching and amplification where reliability, thermal performance, and ease of drive are critical.

FAQ

What is the maximum continuous collector current rating for the MJD128T4?

The MJD128T4 is rated for 8 A continuous collector current (I_C) at case temperature T_C = 25°C. This rating assumes proper heatsinking and adherence to the thermal derating curve (0.16 W/°C above 25°C). At elevated case temperatures, the allowable current must be reduced accordingly to maintain junction temperature below 150°C. The MJD128T4 also supports 16 A peak current for short durations within its safe operating area limits.

Does the MJD128T4 have built-in base-emitter resistors?

Yes, the MJD128T4 features monolithic construction with built-in base-emitter shunt resistors. These resistors provide a defined discharge path for base charge, ensuring reliable turn-off without requiring external components. This design simplifies circuit implementation in relay drivers and switching regulators, reduces component count, and improves consistency in switching timing across production units. The MJD128T4 datasheet explicitly confirms this feature in its "Features" section.

What package type does the MJD128T4 use, and what are its thermal characteristics?

The MJD128T4 uses the DPAK (Case 369C) surface-mount package with four terminals, including an exposed collector tab (Pin 4) for thermal conduction. Its thermal resistance is R_JC = 6.25 °C/W (junction-to-case) and R_JA = 71.4 °C/W (junction-to-ambient) when mounted on the minimum recommended PCB pad size. Effective thermal management requires soldering Pin 4 to a large copper area or external heatsink to sustain rated power dissipation.

Can the MJD128T4 be used in complementary pairs with an NPN Darlington transistor?

Yes, the MJD128T4 is specifically designed as the PNP complement to the NPN MJD112T4. Both share identical DPAK packaging, voltage/current ratings (120 V, 8 A, 20 W), DC current gain (h_FE ≈ 2500 typ.), and thermal specifications. This pairing enables balanced push-pull output stages in audio amplifiers, full-bridge motor drivers, and symmetrical power supplies where matched performance and layout simplicity are required.

What is the typical DC current gain (h_FE) of the MJD128T4, and at what conditions is it specified?

The MJD128T4 has a typical DC current gain (h_FE) of 2500 at I_C = 4.0 A and V_CE = 4 V, with a guaranteed minimum of 1000 under those same conditions. The gain remains usable down to I_C = 100 mA and up to I_C = 8 A, though it decreases at higher currents. This high gain enables low-base-drive operation-e.g., 80 mA base current suffices to saturate the MJD128T4 at 8 A collector current-reducing driver complexity and power loss.