onsemi MJD340T4

Overview

MJD340T4 from ON Semiconductor is a high-voltage NPN epitaxial silicon power transistor in D-PAK surface-mount package, rated for 300 V V_CEO, 0.5 A DC collector current, and 15 W collector dissipation at T_C = 25°C; used in flyback converters, relay drivers, and industrial switch-mode power supplies.

For engineers reviewing the MJD340T4 datasheet, pinout, applications, or equivalent options, key selection criteria include V_CEO/V_CBO rating, h_FE range at 50 mA, saturation voltage under pulsed conditions, thermal derating behavior, and D-PAK footprint compatibility with PCB layout constraints.

Technical Context

This device operates as a single NPN bipolar junction transistor optimized for high-voltage switching in medium-power applications. It features a minimum V_CEO(sus) of 300 V at I_C = 1 mA and I_B = 0, with h_FE ranging from 30 to 240 at V_CE = 10 V and I_C = 50 mA.

Thermal performance is defined by a 15 W maximum collector dissipation at case temperature T_C = 25°C, derating linearly above 25°C at 0.12 W/°C, and a maximum junction temperature of 150°C. Safe operating area (SOA) curves confirm capability under pulsed conditions up to 750 mA with 100 µs pulse width.

Key Specifications

Pinout & Package

D-PAK (TO-252) surface-mount package with standard 3-pin configuration: 1–Base, 2–Collector, 3–Emitter; lead-formed for automated assembly and compatible with IPC-7351B footprint.

Key Features

Applications

Equivalent & Alternatives

The following parts are listed as comparable options for similar high-voltage NPN transistor applications.

Compared with MJD340T4, MJD350T4 offers identical voltage and power ratings but reduced h_FE assurance, while STN3PF30 replaces bipolar operation with MOSFET advantages-requiring gate drive redesign but eliminating base current losses and improving efficiency above 50 kHz.

Availability

MJD340T4 is available at Aetrix Electronics and suitable for switch-mode power supplies, relay driver circuits, DC motor control, and high-voltage LED drivers requiring stable component supply and long-term industrial availability.

Supply support for MJD340T4 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 MJD340T4 belongs to ON Semiconductor's high-voltage bipolar transistor product line, designed specifically for ruggedized medium-power switching in industrial power conversion and control systems.

FAQ

What is the maximum continuous collector current rating for MJD340T4?

The MJD340T4 has a DC collector current rating of 0.5 A at T_C = 25°C. This value decreases with rising case temperature due to thermal derating-specifically at 0.12 W/°C beyond 25°C. For reliable operation at elevated ambient temperatures, users must verify actual I_C against the published power derating curve and SOA limits. The MJD340T4 datasheet confirms this rating applies under steady-state conditions with adequate heatsinking.

Does MJD340T4 have a built-in base-emitter resistor?

No, the MJD340T4 is a standard three-terminal NPN bipolar transistor without any integrated base-emitter resistors. It requires an external base current limiting resistor to ensure proper saturation and prevent thermal runaway. The device's h_FE range (30–240) means base drive design must accommodate both minimum and maximum gain extremes. This characteristic distinguishes MJD340T4 from digital transistors like the NSM3N045, which integrate bias resistors.

What package type is used for MJD340T4 and is the tab electrically connected?

The MJD340T4 uses the D-PAK (TO-252) surface-mount package. Its metal tab is electrically connected to Pin 2 (Collector), not to the emitter or base. This configuration requires careful PCB layout to avoid unintended shorting-especially when mounting to a heatsink or ground plane. The D-PAK footprint matches IPC-7351B standards, and mechanical dimensions are fully documented in the ON Semiconductor MJD340T4 datasheet revision A2.

Can MJD340T4 replace MJD350T4 in existing designs?

MJD340T4 can replace MJD350T4 in most applications due to identical voltage ratings (300 V V_CEO) and power dissipation (15 W), but with higher guaranteed h_FE (min 30 vs. min 20). However, designers must verify base drive circuitry supports the higher gain-particularly in linear or analog-regulator roles where excessive h_FE may cause instability. No PCB changes are required since both share the same D-PAK package and pinout.

What is the safe operating area (SOA) limitation for MJD340T4 at 100 µs pulse width?

At 100 µs pulse width, the MJD340T4 SOA curve supports up to approximately 0.75 A at 100 V V_CE, consistent with its I_CP = 0.75 A pulse rating (PW ≤ 300 µs, duty ≤ 2%). This enables short-duration overload handling in motor start-up or fault-clearing scenarios. Engineers must cross-check actual operating points against the SOA graph in Figure 3 of the MJD340T4 datasheet, as second breakdown limits apply at higher voltages and currents.