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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Single Bipolar Transistors

STMicroelectronics MJD340T4

Name: MJD340T4
Brand: STMicroelectronics
SKU: MJD340T4
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: MJD340T4

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-252-3, DPAK (2 Leads + Tab), SC-63

Datasheet:: MJD340T4.pdf

Description:: TRANS NPN 300V 0.5A DPAK

Quantity:: RFQ Add To RFQ list

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Inventory:7,673

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Product details

Overview

MJD340T4 from STMicroelectronics is a complementary NPN silicon power transistor in TO-252 (DPAK) surface-mount package, rated for 300 V V_CEO, 0.5 A I_C, and 15 W P_tot at T_case ≤ 25 °C, used as a medium-voltage switching element in solenoid/relay driver circuits.

For engineers reviewing the MJD340T4 datasheet, MJD340T4 pinout, MJD340T4 application, or MJD340T4 equivalent, key selection criteria include V_CEO = 300 V, h_FE = 30–240 at I_C = 50 mA, V_CE(sat) ≤ 1.5 V, rugged SOA performance, and DPAK thermal resistance R_thj-case = 8.33 °C/W.

Technical Context

The MJD340T4 is a medium-voltage, general-purpose NPN power transistor fabricated using ST's Medium Voltage Epitaxial-Planar process, enabling high breakdown voltage (V_CBO = V_CEO = 300 V) with robust safe operating area (SOA) and pulsed current capability up to 0.75 A.

It operates with low saturation voltage (V_CE(sat) ≤ 1.5 V at I_C = 0.5 A), DC current gain of 30–240 at 50 mA/10 V, and supports continuous junction temperatures up to 150 °C - optimized for unidirectional switching in industrial control loads.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	300 V - supports switching inductive loads up to 300 V DC bus without avalanche stress
I_C	0.5 A continuous - suitable for driving 24–48 V solenoids and relays with coil currents ≤ 500 mA
P_tot	15 W at T_case ≤ 25 °C - requires heatsinking above ~3 W dissipation in PCB-mounted DPAK layout
h_FE	30–240 at I_C = 50 mA, V_CE = 10 V - enables reliable base drive design with margin for temperature drift
R_thj-case	8.33 °C/W - allows direct thermal path to copper pour or heatsink pad for stable operation at full current
V_CE(sat)	≤ 1.5 V at I_C = 0.5 A - limits conduction loss to ≤ 0.75 W, reducing thermal burden in relay drivers

Pinout & Package

TO-252 (DPAK) surface-mount package with exposed drain pad (pin 2) for thermal conduction; standard 3-pin configuration: emitter (pin 1), base (pin 2), collector (pin 3).

Pin/Terminal	Circuit Role	Design Meaning
Pin 1	Emitter	Low-side return path; connected to ground or load common in high-side switch configurations
Pin 2	Base	Current-controlled input; requires 5–15 mA drive for full saturation at 500 mA collector current
Pin 3	Collector	High-voltage output node; electrically tied to exposed thermal pad for heat transfer to PCB copper

Key Features

Feature	Design Value
Medium Voltage Epitaxial-Planar Process	Enables 300 V breakdown with controlled leakage (I_CBO ≤ 0.1 mA) and stable h_FE across temperature
Rugged Safe Operating Area (SOA)	Supports inductive turn-off without secondary breakdown up to 300 V × 0.5 A DC or pulsed conditions
DPAK Thermal Performance	R_thj-amb = 100 °C/W (standard PCB) and R_thj-case = 8.33 °C/W - enables >10 W dissipation with minimal heatsink
Complementary Pairing	Matched with MJD350 (PNP) for push-pull or H-bridge stages requiring symmetrical voltage/current ratings

Applications

Solenoid Driver

Relay Interface Circuit

Use Scenario: Driving 24 V DC solenoids in industrial valve control systems with intermittent duty cycle.

IC Role / Device Role / Timing Role: NPN power switch controlling current flow through solenoid coil; turned on/off by microcontroller GPIO via base resistor.

Use Value: 300 V rating prevents failure during back-EMF transients; V_CE(sat) ≤ 1.5 V minimizes self-heating during 500 ms activation pulses.

Use Scenario: Isolating PLC output signals to energize 48 V DC electromagnetic relays in factory automation panels.

IC Role / Device Role / Timing Role: High-side or low-side switching element interfacing logic-level control to relay coil supply rail.

Use Value: h_FE ≥ 30 ensures reliable saturation with ≤ 15 mA base drive; SOA withstands relay coil de-energization spikes.

DC Motor Commutation Stage

Linear Regulator Pass Element

Use Scenario: Half-bridge upper-leg switch in 24 V brushed DC motor control for HVAC actuators.

IC Role / Device Role / Timing Role: NPN transistor switching motor phase voltage; paired with MJD350 for complementary drive.

Use Value: Matched V_CEO/I_C ratings enable balanced voltage sharing; DPAK footprint simplifies dual-transistor layout.

Use Scenario: Series pass transistor in adjustable linear regulator supplying 5 V/1 A to analog sensor circuitry.

IC Role / Device Role / Timing Role: Current-regulating element dissipating excess voltage between unregulated input and regulated output.

Use Value: 15 W P_tot and 8.33 °C/W R_thj-case support ≥ 8 W continuous dissipation with PCB heatsinking.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJE340	TO-220 through-hole package; identical V_CEO, I_C, h_FE, but higher R_thj-amb (125 °C/W)	Requires mechanical mounting and heatsink; unsuitable for dense SMT layouts	Select when board space permits through-hole assembly and thermal mass is available
BD241C	Lower V_CEO = 100 V; h_FE = 40–250; same DPAK package but reduced voltage margin	Not suitable for 300 V bus applications; limited to ≤ 100 V DC switching	Select only for cost-sensitive 24–48 V systems where 300 V rating is unnecessary

Compared with MJE340, MJD340T4 offers superior thermal efficiency in SMT designs; compared with BD241C, it provides critical 300 V capability for industrial solenoid and relay drivers where transient overvoltage is present.

Availability

MJD340T4 is available at Aetrix Electronics and suitable for solenoid drivers, relay interface circuits, and DC motor commutation stages 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, designing and manufacturing analog, power, MCU, and sensor solutions for industrial, automotive, and consumer markets.

The MJD series targets cost-effective, rugged power switching in industrial controls - emphasizing medium-voltage capability, SOA robustness, and surface-mount compatibility for automated assembly.

FAQ

What is the maximum continuous collector current for MJD340T4 at 70 °C case temperature?

The MJD340T4 is rated for 0.5 A I_C at T_case ≤ 25 °C. Derating is linear at 6.7 mA/°C above 25 °C, resulting in ~0.33 A maximum continuous collector current at 70 °C case temperature per the datasheet's thermal derating curve.

Can MJD340T4 be used in parallel for higher current handling?

No - MJD340T4 lacks built-in emitter ballasting resistors and exhibits positive thermal feedback. Parallel operation without external current-sharing resistors risks thermal runaway; ST does not recommend or characterize this configuration in the official datasheet.

Is the exposed pad on the DPAK package electrically connected?

Yes - the exposed thermal pad (pin 3, collector) is electrically connected to the collector terminal. It must be soldered to a PCB copper pour tied to the collector net and thermally isolated from other nets to avoid short circuits and ensure proper heat transfer.

Does MJD340T4 require a flyback diode when driving inductive loads?

Yes - although the device has no integrated clamp, a fast-recovery or Schottky flyback diode (e.g., 1N5819) must be placed across the solenoid or relay coil to suppress inductive kickback and prevent V_CE overshoot beyond 300 V during turn-off.

MJD340T4 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-252-3, DPAK (2 Leads + Tab), SC-63

Packaging:: Tape & Reel (TR)

Product Status:: Active

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 500 mA

Voltage - Collector Emitter Breakdown (Max):: 300 V

Vce Saturation (Max) @ Ib, Ic:: -

Current - Collector Cutoff (Max):: 100µA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 30 @ 50mA, 10V

Power - Max:: 15 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: DPAK

MJD340T4 FAQ

1.How can I place an order for MJD340T4 through Aetrix?

Please submit a Request for Quotation (RFQ) for MJD340T4 on Aetrix. Our sales agent will provide a competitive quotation and guide you through the order confirmation once you accept the terms.

2.Are the price and stock information for MJD340T4 reliable?

The price and inventory of MJD340T4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MJD340T4 is usually 5 days.

3.What payment methods are accepted for MJD340T4?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MJD340T4 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for MJD340T4?

MJD340T4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your MJD340T4 order is processed, you will receive an email with the shipment details and tracking number.

Note: Tracking information may take up to 24 hours to appear. Express delivery typically takes 3–5 business days.

5.How can I obtain technical support or documentation for MJD340T4?

For technical support, including MJD340T4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MJD340T4 requirements.

6.How does Aetrix verify that MJD340T4 is sourced from the original manufacturer or authorized distributors?

All MJD340T4 products on Aetrix are procured from qualified distributors and authorized channels. Our dedicated quality assurance team conducts strict verification, including traceability checks and, if necessary, third-party testing. This ensures that MJD340T4 meets industry standards.

7.What is the process for return or replacement of MJD340T4?

All MJD340T4 units undergo pre-shipment inspection (PSI). If there is an issue with MJD340T4, returns or replacements are accepted under the following conditions:

1.Quantity discrepancies, incorrect items, or visible external defects (such as breakage or corrosion), acknowledged by Aetrix.

2.The issue is reported within 90 days of delivery.

3.The MJD340T4 part is unused and in its original packaging.

Return procedure for MJD340T4:

1.Submit a request within 90 days.

2.Obtain a Return Material Authorization (RMA) from Aetrix.

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