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Home > Products > Discrete Semiconductor Products > Transistors > Bipolar (BJT) > Bipolar Transistor Arrays

STMicroelectronics STD840DN40

Name: STD840DN40
Brand: STMicroelectronics
SKU: STD840DN40
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: STD840DN40

Manufacturer:: STMicroelectronics

Category:: Bipolar Transistor Arrays

Package:: 8-DIP (0.300", 7.62mm)

Datasheet:: STD840DN40.pdf

Description:: TRANS 2NPN DUAL 400V 4A 8-DIP

Quantity:: RFQ Add To RFQ list

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Inventory:9,831

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Product details

Overview

STD840DN40 from STMicroelectronics is a dual NPN high-voltage power transistor in a single DIP-8 package, rated for V_CEO = 400 V, I_C = 4 A, and R_thJC = 2.7 °C/W per transistor. It features low V_CE(sat) (0.5 V @ 1 A/0.2 A), fast switching (t_s = 2.5 μs, t_f = 0.2 μs), and integrated freewheel diodes-designed specifically for compact fluorescent lamp (CFL) electronic ballasts operating directly from 220 V mains.

For engineers reviewing the STD840DN40 datasheet, STD840DN40 pinout, STD840DN40 application, or STD840DN40 equivalent, key selection criteria include high-voltage blocking capability (V_CEO = 400 V), dual-transistor integration for half-bridge or push-pull topologies, thermal performance under case-constrained conditions, and verified switching behavior in resistive-load CFL driver circuits.

Technical Context

This device implements two independent NPN transistors fabricated using multi-epitaxial planar technology, each with separate collector, base, and emitter terminals routed to distinct pins in the dual-island DIP-8 package. The internal structure enables high mounting flexibility and electrical isolation between channels.

Each transistor supports sustained operation at T_J = 150 °C, delivers h_FE ≥ 10 (IC = 10 mA, V_CE = 5 V) and ≥ 8 (IC = 2 A, V_CE = 5 V), and includes an integrated freewheel diode (V_F = 2.5 V @ 1 A) for inductive load management in ballast drivers.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	400 V - Sustains full 220 V AC mains with safety margin in CFL ballast switch nodes
I_C	4 A continuous - Supports >25 W lamp drive with headroom for surge currents
V_CE(sat)	0.5 V @ 1 A/0.2 A - Minimizes conduction loss and thermal stress in high-duty-cycle operation
t_s/t_f	2.5 μs / 0.2 μs - Enables efficient 20–60 kHz switching in resonant CFL ballast topologies
R_thJC	2.7 °C/W - Allows direct heatsinking of each transistor island for stable thermal management
V_F (diode)	2.5 V @ 1 A - Provides controlled freewheeling path without external diode in half-bridge configurations
T_J(max)	150 °C - Rated for continuous operation in enclosed, thermally constrained lamp housings

Pinout & Package

The STD840DN40 is housed in a dual-island DIP-8 package with physically separated terminal islands for electrical isolation and flexible PCB layout. Pin numbering follows standard DIP-8 orientation (pin 1 at top-left corner).

Pin/Terminal	Circuit Role	Design Meaning
1	Emitter 1	Low-side return path for first transistor; isolated from E2 for independent grounding
2	Base 1	Drive input for first transistor; requires current-limited bias for safe turn-on
3	Collector 1	High-voltage switch node; connects to lamp resonant tank or DC bus
4	Collector 2	Second high-voltage switch node; enables complementary or parallel operation
5	Base 2	Independent drive input for second transistor; supports push-pull timing control
6	Emitter 2	Isolated return for second transistor; allows floating or differential emitter referencing
7	No connection	Internal isolation barrier; no electrical function
8	No connection	Internal isolation barrier; no electrical function

Key Features

Feature	Design Value
Dual NPN topology in one DIP-8	Reduces board space by ~40% vs. discrete dual-transistor solutions in CFL ballasts
Separate collector/emitter islands	Enables independent thermal sinking and eliminates cross-talk in high-dV/dt lighting environments
Integrated freewheel diode per transistor	Eliminates need for two external diodes in half-bridge resonant drivers
V_CE(sat) ≤ 0.5 V @ 1 A	Lowers conduction loss to <0.5 W per transistor at nominal lamp current
R_thJC = 2.7 °C/W	Supports 45 W total dissipation per transistor when mounted on metal-core PCB or heatsink

Applications

Compact Fluorescent Lamp (CFL) Ballast

LED Driver with Resonant Topology

Use Scenario: 220 V AC-powered CFL module with integrated electronic ballast driving 18–36 W lamps.

IC Role / Device Role / Timing Role: Dual NPN switch pair implementing half-bridge inverter stage; operates at 25–50 kHz with zero-voltage switching.

Use Value: Eliminates four discrete transistors and two diodes; reduces component count by 6 parts while maintaining thermal separation.

Use Scenario: High-efficiency LED driver for street lighting using LLC resonant converter with 300–400 V DC bus.

IC Role / Device Role / Timing Role: Primary-side synchronous switch pair handling high-voltage, medium-current switching in resonant tank interface.

Use Value: Leverages 400 V V_CEO rating and fast t_f = 0.2 μs to minimize switching losses at 300 kHz operation.

AC-DC Flyback Auxiliary Supply

Industrial Solenoid Driver

Use Scenario: Auxiliary 12 V/1 A supply in industrial PLC power modules, deriving power from 230 V AC input.

IC Role / Device Role / Timing Role: High-voltage NPN switch controlling primary-side flyback transformer; driven by UC384x controller.

Use Value: Uses V_CEO = 400 V rating to withstand reflected voltage spikes without snubber overhead.

Use Scenario: 24 V DC solenoid actuator control in HVAC valve systems requiring fast turn-off and inductive energy recovery.

IC Role / Device Role / Timing Role: Low-loss switching element with integrated freewheel diode managing 2 A inductive load current.

Use Value: Freewheel diode V_F = 2.5 V ensures predictable decay time and suppresses voltage overshoot during de-energization.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
STN840D	Single NPN in TO-220; same V_CEO/I_C but no dual integration or freewheel diodes	Requires two devices + external diodes for ballast use; higher board area and thermal coupling	Choose only if discrete layout and individual thermal optimization are required
BU508AF	Dual NPN in ISOWATT-218; V_CEO = 1500 V, I_C = 8 A, but slower switching (t_f > 1 μs) and no integrated diodes	Better for high-voltage surge-prone environments (e.g., outdoor signage), not optimized for high-frequency CFL	Select when overvoltage robustness > switching efficiency; avoid for >30 kHz designs

Compared with STN840D and BU508AF, the STD840DN40 uniquely combines dual-channel integration, built-in freewheel diodes, and sub-microsecond fall time-making it the only option that reduces BOM count *and* maintains high-frequency efficiency in CFL ballasts.

Availability

STD840DN40 is available at Aetrix Electronics and suitable for compact fluorescent lamp (CFL) ballasts, resonant LED drivers, and industrial solenoid controllers requiring stable component supply across extended production lifecycles.

Supply support for STD840DN40 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, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The STD840DN40 belongs to ST's high-voltage bipolar transistor product line, engineered specifically for energy-efficient lighting control and high-reliability industrial switching applications where integration, thermal performance, and ruggedness are critical.

FAQ

What is the maximum safe operating frequency for STD840DN40 in a CFL ballast?

The device is characterized for resistive-load switching up to 60 kHz with t_s = 2.5 μs and t_f = 0.2 μs. In practical CFL resonant ballasts, it reliably operates at 25–50 kHz with proper gate drive and layout; exceeding 60 kHz increases switching loss disproportionately due to stored charge effects.

Can STD840DN40 be used in avalanche mode?

No-STD840DN40 is not rated for repetitive avalanche operation. Its absolute maximum V_CEO = 400 V is a DC sustaining voltage under specified test conditions (IB = 0, IC = 10 mA); operation beyond this without clamping risks irreversible junction failure.

How should the dual-island DIP-8 package be thermally managed?

Each transistor island must be independently heatsunk via copper pour or clip-on heatsinks. The R_thJC = 2.7 °C/W rating assumes direct thermal contact to case; shared heatsinking between islands invalidates the spec and risks thermal runaway due to cross-coupling.

Are pins 7 and 8 internally connected or electrically isolated?

Pins 7 and 8 are internal isolation barriers with no electrical connection-confirmed in ST's mechanical drawing (Doc ID 16796 Rev 3, Figure 9). They serve only structural and creepage-enhancing functions and must remain unconnected in PCB layout.

STD840DN40 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: 8-DIP (0.300", 7.62mm)

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: 2 NPN (Dual)

Current - Collector (Ic) (Max):: 4A

Voltage - Collector Emitter Breakdown (Max):: 400V

Vce Saturation (Max) @ Ib, Ic:: 1V @ 400mA, 2A

Current - Collector Cutoff (Max):: 250µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 8 @ 2A, 5V

Power - Max:: 3W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: 8-DIP

STD840DN40 FAQ

1.How can I place an order for STD840DN40 through Aetrix?

Please submit a Request for Quotation (RFQ) for STD840DN40 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 STD840DN40 reliable?

The price and inventory of STD840DN40 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for STD840DN40 is usually 5 days.

3.What payment methods are accepted for STD840DN40?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for STD840DN40 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for STD840DN40?

STD840DN40 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your STD840DN40 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 STD840DN40?

For technical support, including STD840DN40 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your STD840DN40 requirements.

6.How does Aetrix verify that STD840DN40 is sourced from the original manufacturer or authorized distributors?

All STD840DN40 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 STD840DN40 meets industry standards.

7.What is the process for return or replacement of STD840DN40?

All STD840DN40 units undergo pre-shipment inspection (PSI). If there is an issue with STD840DN40, 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 STD840DN40 part is unused and in its original packaging.

Return procedure for STD840DN40:

1.Submit a request within 90 days.

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

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