onsemi MJD340TF

Overview

MJD340TF 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. It serves as a switching element in flyback converters, relay drivers, and industrial motor control circuits requiring robust voltage blocking and pulse-current capability.

For engineers reviewing the MJD340TF datasheet, pinout, applications, or equivalent options, key selection criteria include its 300 V sustaining voltage (V_CEO(sus)), h_FE range of 30–240 at 50 mA, low saturation voltage (V_CE(sat) ≤ 1.5 V @ I_C = 0.5 A), and thermal performance in surface-mount power applications.

Technical Context

The MJD340TF operates as a single NPN bipolar junction transistor optimized for high-voltage switching rather than linear amplification. Its design emphasizes safe operating area (SOA) integrity under pulsed conditions (PW ≤ 300 µs, duty cycle ≤ 2%) and thermal stability up to 150°C junction temperature.

It features a D-PAK (TO-252) package with three terminals-Base, Collector, Emitter-configured in standard 1-2-3 pin order. The device exhibits V_BE(sat) ≤ 2.0 V at I_C = 0.5 A and I_B = 50 mA, supporting reliable turn-on in gate-driver-coupled or resistor-biased configurations.

Key Specifications

Pinout & Package

D-PAK (TO-252) surface-mount package with exposed drain-connected tab (Collector) for thermal conduction; lead-formed for automated placement and reflow soldering.

Key Features

Applications

Equivalent & Alternatives

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

Compared with MJD340TF, MJD350TF serves only complementary roles and cannot substitute directly, while STN3PF30 offers faster switching and zero gate current but demands gate drive circuitry-making MJD340TF preferable for cost-sensitive, low-to-mid frequency (<100 kHz), resistor-biased applications.

Availability

MJD340TF is available at Aetrix Electronics and suitable for industrial motor control, switch-mode power supply design, and high-voltage relay driving requiring stable component supply and long-term production continuity.

Supply support for MJD340TF 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 connectivity solutions for automotive, industrial, and cloud power applications.

The MJD340TF belongs to ON Semiconductor's legacy high-voltage bipolar transistor product line, originally developed by Fairchild for ruggedized industrial switching applications demanding reliability under voltage stress and thermal cycling.

FAQ

What is the maximum continuous collector current rating for MJD340TF?

The MJD340TF has a maximum DC collector current (I_C) rating of 0.5 A at case temperature T_C = 25°C. This rating decreases with rising case temperature per the derating curve in Figure 4 of the datasheet; at T_C = 100°C, usable I_C drops to approximately 0.25 A. Designers must ensure adequate PCB copper area or heatsinking to maintain T_C within limits for the target load.

Does MJD340TF have a built-in protection diode?

No, the MJD340TF does not integrate any protection diode. As a discrete NPN bipolar transistor, it requires an external flyback diode (e.g., 1N4007 or fast recovery type) across inductive loads such as relays or motors to clamp inductive kickback and prevent secondary breakdown. This is explicitly required in all relay driver and motor control applications using the MJD340TF.

What package type is used for MJD340TF and how is it mounted?

The MJD340TF uses the D-PAK (TO-252) surface-mount package with three leads and an exposed metal tab that connects internally to the Collector terminal. It is designed for reflow soldering onto PCBs with thermal pad connection to internal ground or heatsink plane. The lead-formed variant (no suffix) is optimized for pick-and-place assembly and requires no post-solder forming.

Can MJD340TF replace older Fairchild MJD340 devices?

Yes, the MJD340TF is the ON Semiconductor–branded successor to the original Fairchild MJD340, retaining identical electrical specifications, pinout, package dimensions, and thermal characteristics. The "TF" suffix denotes tape-and-reel packaging and conforms to ON Semiconductor's updated nomenclature following the Fairchild integration; no design changes or performance deviations are introduced.

What is the typical DC current gain (h_FE) of MJD340TF at operating conditions?

The MJD340TF exhibits a DC current gain (h_FE) ranging from 30 to 240 when measured at V_CE = 10 V and I_C = 50 mA. Gain varies significantly with collector current and temperature; at I_C = 0.5 A, h_FE typically falls to 20–40. Designers should verify base drive sufficiency across the full operating range, especially near maximum current, to ensure saturation.