My Inquiry
My Account
STMicroelectronics MJE340
- Part No.:
- MJE340
- Manufacturer:
- STMicroelectronics
- Category:
- Single Bipolar Transistors
- Package:
- TO-225AA, TO-126-3
- Datasheet:
-
MJE340.pdf
- Description:
- TRANS NPN 300V 0.5A SOT-32-3
- Quantity:
- Payment:
- Shipping:
Inventory:2,552
Please send an inquiry. Send us your inquiry, and we will respond immediately.
Product details
Overview
MJE340 from STMicroelectronics is a silicon planar NPN power transistor in SOT-32 (TO-126) package, rated for 300 V VCBO, 0.5 A IC, and 20.8 W total dissipation at Tc ≤ 25 °C, used in medium-power linear amplifiers and switching regulators for industrial control systems.
For engineers reviewing the MJE340 datasheet, MJE340 pinout, MJE340 application, or MJE340 equivalent, key selection criteria include its 300 V collector-base voltage rating, 0.5 A continuous collector current capability, 6.0 °C/W junction-to-case thermal resistance, and complementary pairing with MJE350 for push-pull output stages.
Technical Context
The MJE340 operates as a medium-power bipolar junction transistor with fixed NPN polarity, designed for linear amplification and hard-switching duty where high breakdown voltage and moderate current handling are required. Its DC current gain ranges from 30 to 240 at IC = 50 mA and VCE = 10 V.
It features a safe operating area defined up to 300 V and 0.5 A under pulsed conditions, with VCE(sat) ≤ 0.5 V at IC = 100 mA and IB = 10 mA, and VBE(on) ≈ 1 V at IC = 50 mA and VCE = 10 V - confirming suitability for base-driven Class AB and switching topologies.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCBO | 300 V - supports high-voltage collector bias in line-powered industrial supplies |
| IC (max) | 0.5 A - enables medium-current driver stage operation without forced cooling |
| PTOT @ Tc ≤ 25°C | 20.8 W - allows direct mounting on heatsink for sustained power dissipation |
| RthJC | 6.0 °C/W - ensures predictable thermal path from junction to case for thermal design |
| hFE | 30–240 - provides stable current amplification across production lots at 50 mA bias |
| VCE(sat) | ≤0.5 V @ IC=100 mA, IB=10 mA - minimizes conduction loss in saturated switch mode |
Pinout & Package
Package: SOT-32 (TO-126), through-hole, single-ended metal tab for heatsinking. Tab is electrically connected to collector.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Collector (Tab) | Main current sink terminal | Electrically tied to metal tab; must be isolated from chassis unless common-collector configuration is intended |
| Base | Current-controlled input | Receives forward-biased drive current to modulate collector current; requires series resistor for current limiting |
| Emitter | Current source reference terminal | Provides low-impedance return path; typically grounded or connected to load return in common-emitter topology |
Key Features
| Feature | Design Value |
|---|---|
| High VCBO rating | 300 V enables use in 240 VAC line-derived supplies without derating |
| Complementary pair availability | MJE350 PNP counterpart supports balanced push-pull amplifier designs |
| Low VCE(sat) | ≤0.5 V reduces power loss and heat generation during saturation |
| Robust SOA | Defined safe operating area up to 300 V/0.5 A supports transient overloads in industrial environments |
Applications
| Industrial Linear Amplifier | Switch-Mode Power Supply Driver |
|---|---|
Use Scenario: Medium-power audio or signal amplification stage in programmable logic controller (PLC) analog output modules. IC Role / Device Role / Timing Role: NPN power transistor configured in common-emitter topology to deliver 0–10 V or 4–20 mA output signals. Use Value: 300 V VCBO withstands back-EMF from inductive loads; 20.8 W dissipation supports continuous 100 mA output without active cooling. | Use Scenario: Main switching element in offline flyback or forward converter auxiliary power supply. IC Role / Device Role / Timing Role: Primary-side NPN switch driven by UC384x controller to regulate 12 V/500 mA auxiliary rail. Use Value: 0.5 V VCE(sat) limits conduction loss; 6.0 °C/W RthJC simplifies heatsink sizing for 25 kHz switching. |
| DC Motor Control Stage | High-Voltage Relay Driver |
Use Scenario: H-bridge half-bridge leg in 24–48 V brushed DC motor controllers for factory automation actuators. IC Role / Device Role / Timing Role: NPN switch in totem-pole or discrete driver stage controlling motor winding current direction and magnitude. Use Value: 300 V rating accommodates inductive kickback up to 250 V; hFE range ensures reliable turn-on with standard microcontroller GPIO drive. | Use Scenario: High-side driver for 120/240 VAC solid-state relays in HVAC control panels. IC Role / Device Role / Timing Role: Series-pass transistor isolating logic-level MCU outputs from AC load switching circuitry. Use Value: 300 V VCEO(sus) sustains full mains voltage during zero-crossing transitions; TO-126 tab enables direct heatsink mounting for 100% duty cycle operation. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar NPN power transistor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| 2N3055 | TO-3 package, higher PTOT (115 W), lower hFE (20–100), no complementary PNP in same package | Requires larger heatsink and mechanical mounting; not drop-in compatible due to footprint and gain variation | Select when higher power and legacy board compatibility outweigh SOT-32 space constraints |
| TIP41C | Same SOT-32 package, lower VCBO (100 V), higher IC (6 A), higher PTOT (65 W) | Unsuitable for >100 V applications but better for high-current, low-voltage motor drives | Select for 24–48 V systems requiring higher current headroom and identical footprint |
Compared with 2N3055 and TIP41C, MJE340 offers optimal balance of high-voltage capability (300 V), compact SOT-32 packaging, and verified complementary pairing with MJE350 - making it preferred for space-constrained industrial linear and switching designs requiring precise bipolar symmetry.
Availability
MJE340 is available at Aetrix Electronics and suitable for industrial linear amplifiers, switch-mode power supply drivers, DC motor control stages, and high-voltage relay drivers requiring stable component supply and long-term manufacturing continuity.
Supply support for MJE340 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, Switzerland, designing and manufacturing analog, digital, and mixed-signal ICs and discrete devices for industrial, automotive, and consumer markets.
The MJE340 belongs to ST's legacy silicon power transistor product line, engineered specifically for robust, cost-effective medium-power linear and switching applications in industrial equipment where reliability and voltage margin are critical.
FAQ
Is the MJE340 RoHS-compliant?
Yes, the MJE340 is manufactured in ECOPACK®-compliant versions per STMicroelectronics' environmental program. The device meets RoHS Directive 2011/65/EU requirements, with lead-free terminations and halogen-free molding compounds confirmed in official ST documentation and distributor certifications.
What is the maximum continuous collector current at 70°C case temperature?
At Tc = 70 °C, the MJE340's maximum continuous collector current is derated to approximately 0.35 A, based on its 6.0 °C/W RthJC and 150 °C max junction temperature. This follows the linear derating curve shown in Figure 3 of ST's Doc ID 4171 Rev 6.
Can MJE340 be used in avalanche mode?
No, the MJE340 is not rated or characterized for controlled avalanche operation. Its safe operating area excludes secondary breakdown under unclamped inductive switching, and ST does not specify avalanche energy ratings - use only within absolute maximum ratings and SOA boundaries.
Does the metal tab connect to collector, base, or emitter?
The metal tab of the SOT-32 (TO-126) package is internally connected to the collector terminal. This is confirmed in ST's mechanical drawings (Figure 8) and electrical schematics (Figure 1), requiring electrical isolation from the heatsink unless the collector is referenced to chassis ground.
MJE340 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- STMicroelectronics
- Series:
- -
- Package/Case:
- TO-225AA, TO-126-3
- Packaging:
- Tube
- 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:
- 20.8 W
- Frequency - Transition:
- -
- Operating Temperature:
- 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Through Hole
- Supplier Device Package:
- SOT-32-3
MJE340 FAQ
1.How can I place an order for MJE340 through Aetrix?
Please submit a Request for Quotation (RFQ) for MJE340 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 MJE340 reliable?
The price and inventory of MJE340 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for MJE340 is usually 5 days.
3.What payment methods are accepted for MJE340?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for MJE340 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for MJE340?
MJE340 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your MJE340 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 MJE340?
For technical support, including MJE340 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your MJE340 requirements.
6.How does Aetrix verify that MJE340 is sourced from the original manufacturer or authorized distributors?
All MJE340 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 MJE340 meets industry standards.
7.What is the process for return or replacement of MJE340?
All MJE340 units undergo pre-shipment inspection (PSI). If there is an issue with MJE340, 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 MJE340 part is unused and in its original packaging.
Return procedure for MJE340:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
MJE340 Tags
-
MMBT3906LT1G
onsemi
-
MMBT3904-7-F
Diodes Incorporated
-
MMBT3904LT1G
onsemi
-
MMBT3906-7-F
Diodes Incorporated
-
MMBT3904-TP
Micro Commercial Co
-
MMBT2222A-7-F
Diodes Incorporated
-
BC846BLT1G
onsemi
-
BC847B,215
Nexperia USA Inc.
-
SMMBT3904LT1G
onsemi
-
MMBT2222A-TP
Micro Commercial Co
-
MMBTA06LT1G
onsemi
-
MMBT2222ALT1G
onsemi
Tech Hub
A practical engineering and sourcing framework covering lifecycle verification, lifetime-buy calculations, replacement qualification, supplier checks and counterfeit-risk controls.
TTL and CMOS logic families differ in thresholds, loading, output drive, power and timing. This engineering guide compares 74HC and 74HCT, calculates noise margins and checks 3.3 V/5 V compatibility.
A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.
The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…
The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…
A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…
A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …
An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…
Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…
An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…
