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

STMicroelectronics 2N3439

Name: 2N3439
Brand: STMicroelectronics
SKU: 2N3439
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: 2N3439

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-205AD, TO-39-3 Metal Can

Datasheet:: 2N3439.pdf

Description:: TRANS NPN 350V 1A TO-39

Quantity:: RFQ Add To RFQ list

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Inventory:6,878

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Product details

Overview

2N3439 from STMicroelectronics is a silicon epitaxial planar NPN transistor in TO-39 metal package, rated for 450 V collector-base voltage, 350 V collector-emitter voltage, and 1 A continuous collector current. It is designed as a high-voltage, low-current driver in line-operated inverters, switching regulators, and series regulators for industrial power supplies.

For engineers reviewing the 2N3439 datasheet, 2N3439 pinout, 2N3439 application, or 2N3439 equivalent, key selection criteria include V_CBO = 450 V, V_CEO = 350 V, I_C = 1 A, h_FE = 40–160 at 20 mA, and R_thj-case = 17.5 °C/W - critical for thermal design in high-voltage linear and switching topologies.

Technical Context

The 2N3439 operates as a medium-power, high-voltage NPN bipolar junction transistor with planar epitaxial construction enabling stable gain and rugged avalanche capability. Its 200 °C maximum junction temperature and 10 W case-rated dissipation support operation in thermally constrained industrial enclosures.

It features pulsed sustaining voltage (V_CEO(sus)) of 350 V at 50 mA, saturation voltages of V_CE(sat) = 0.5 V and V_BE(sat) = 1.3 V under defined drive conditions, and transition frequency f_T = 15 MHz - confirming suitability for <100 kHz switching and linear regulation roles.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CBO	450 V - enables use in 300–400 V DC bus applications without derating
V_CEO	350 V - supports direct connection to rectified 240 VAC mains (≈340 V peak)
I_C	1 A continuous - sufficient for driver-stage current in 50–100 W SMPS or linear regulators
h_FE	40–160 @ 20 mA - provides predictable base drive requirements across production lot
R_thj-case	17.5 °C/W - requires heatsink interface ≤ 5 °C/W to maintain T_j < 150 °C at full P_tot
f_T	15 MHz - adequate for switching up to ~100 kHz with controlled turn-off loss
V_CE(sat)	0.5 V @ I_C = 50 mA, I_B = 4 mA - minimizes conduction loss in saturated-switching mode

Pinout & Package

Package: TO-39 metal can with center lead (Emitter), left lead (Base), right lead (Collector) when viewed from top with tab at 12 o'clock position. Hermetically sealed, electrically isolated case rated for 200 °C junction operation.

Pin/Terminal	Circuit Role	Design Meaning
Center (E)	Emitter	Common reference node; connected to heatsink via insulating washer if case is grounded
Left (B)	Base	Current-controlled input; requires 4 mA drive for 50 mA collector saturation
Right (C)	Collector	High-voltage output node; electrically isolated from case but thermally coupled

Key Features

Feature	Design Value
High V_CBO rating	450 V enables direct use in 240 VAC-derived 340 VDC rails without snubbers
Pulsed V_CEO(sus)	350 V sustains transient overvoltage during inductive turn-off in regulator stages
10 W case power rating	Supports linear operation at 350 V × 20 mA = 7 W with margin for thermal transients
200 °C max junction temp	Permits operation in sealed industrial enclosures with ambient up to 70 °C
Low leakage (ICBO ≤ 20 µA)	Ensures stable bias in high-impedance base networks over temperature and life

Applications

Switching Regulator Driver

Inverter Stage Switch

Use Scenario: Driving the base of a main power switch (e.g., MOSFET or IGBT) in a flyback or forward converter operating from 240 VAC rectified input.

IC Role / Device Role / Timing Role: NPN driver transistor providing level-shifted, current-amplified gate/base drive signal.

Use Value: 350 V V_CEO withstands reflected transformer spikes; 1 A I_C supports >500 mA peak gate charge delivery.

Use Scenario: Low-side switching element in a half-bridge inverter feeding a resonant tank or motor winding from 300–350 VDC bus.

IC Role / Device Role / Timing Role: High-voltage saturated switch controlling current flow through primary inductance.

Use Value: 0.5 V V_CE(sat) limits conduction loss at 100–500 mA loads; TO-39 package allows direct mounting to heatsink.

Series Pass Regulator

High-Voltage Line Monitor

Use Scenario: Series pass element in a discrete 300 V output linear regulator for analog instrumentation or legacy CRT bias supply.

IC Role / Device Role / Timing Role: Voltage-controlled current source dissipating up to 7 W continuously in active region.

Use Value: 10 W P_tot and 17.5 °C/W R_thj-case enable stable 300 V × 20 mA operation with standard heatsinking.

Use Scenario: Overvoltage detection stage sensing rectified AC line voltage before EMI filter or bridge rectifier.

IC Role / Device Role / Timing Role: High-impedance voltage comparator input stage using emitter-follower configuration.

Use Value: ICBO ≤ 20 µA ensures minimal error current at 340 V; 450 V V_CBO prevents breakdown during surge events.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJE13009	V_CEO = 400 V, I_C = 12 A, TO-220 package, lower h_FE (8–40)	Higher current capacity but larger footprint; less suitable for compact driver stages	Prefer when higher I_C and PCB-mounting are required over hermetic sealing
2SC3503	V_CEO = 350 V, I_C = 0.5 A, TO-92 package, f_T = 100 MHz	Lower voltage margin and current rating; optimized for RF amplification, not power switching	Only suitable for low-power, low-voltage signal switching - not a functional replacement

Compared with MJE13009 and 2SC3503, the 2N3439 uniquely balances 450 V standoff, 1 A current, TO-39 hermetic reliability, and 17.5 °C/W thermal resistance - making it irreplaceable in space-constrained, high-reliability line-operated driver designs.

Availability

2N3439 is available at Aetrix Electronics and suitable for industrial power supplies, consumer appliance inverters, and high-voltage linear regulators requiring stable component supply and long-term obsolescence management.

Supply support for 2N3439 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, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

The 2N3439 belongs to ST's legacy high-voltage bipolar transistor product line, engineered specifically for robustness in line-powered equipment where reliability under sustained high-voltage stress is mandatory.

FAQ

Is the 2N3439 RoHS compliant?

Yes, the 2N3439 is RoHS compliant per STMicroelectronics' official product change notification PCN-2006-01. It contains no lead in solderable terminations and meets EU Directive 2011/65/EU requirements, including exemption 7a for high-melting-temperature solder alloys used in TO-39 assembly.

Can the 2N3439 replace the 2N3440 in existing designs?

Yes, but only with voltage derating: the 2N3439 has higher V_CBO (450 V vs. 300 V) and V_CEO (350 V vs. 250 V), identical pinout and package, and overlapping h_FE range. No layout change is needed, though base drive may require minor adjustment due to higher gain variation.

What is the maximum safe operating area (SOA) limit at 100 °C case temperature?

At T_c = 100 °C, P_tot is linearly derated to 5.5 W (per 17.5 °C/W R_thj-case). The SOA boundary at 100 °C is defined by V_CE ≤ 350 V and I_C ≤ 1 A, with pulse limitation to 300 µs/1.5% duty cycle above 250 V to avoid second breakdown.

Does the TO-39 case serve as an electrical terminal?

No, the TO-39 metal case is electrically isolated from all internal terminals. It is internally insulated and intended for thermal mounting only. Electrical connection to the case must be avoided unless explicitly confirmed by ST's mechanical drawings - no internal bonding exists between case and emitter, base, or collector.

2N3439 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-205AD, TO-39-3 Metal Can

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 1 A

Voltage - Collector Emitter Breakdown (Max):: 350 V

Vce Saturation (Max) @ Ib, Ic:: 500mV @ 4mA, 50mA

Current - Collector Cutoff (Max):: 20µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 40 @ 20mA, 10V

Power - Max:: 1 W

Frequency - Transition:: 15MHz

Operating Temperature:: 200°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-39

2N3439 FAQ

1.How can I place an order for 2N3439 through Aetrix?

Please submit a Request for Quotation (RFQ) for 2N3439 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 2N3439 reliable?

The price and inventory of 2N3439 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for 2N3439 is usually 5 days.

3.What payment methods are accepted for 2N3439?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for 2N3439 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for 2N3439?

2N3439 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your 2N3439 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 2N3439?

For technical support, including 2N3439 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your 2N3439 requirements.

6.How does Aetrix verify that 2N3439 is sourced from the original manufacturer or authorized distributors?

All 2N3439 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 2N3439 meets industry standards.

7.What is the process for return or replacement of 2N3439?

All 2N3439 units undergo pre-shipment inspection (PSI). If there is an issue with 2N3439, 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 2N3439 part is unused and in its original packaging.

Return procedure for 2N3439:

1.Submit a request within 90 days.

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

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