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

STMicroelectronics STD878T4

Name: STD878T4
Brand: STMicroelectronics
SKU: STD878T4
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: STD878T4

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

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

Datasheet:: STD878T4.pdf

Description:: TRANS NPN 30V 5A DPAK

Quantity:: RFQ Add To RFQ list

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Product details

Overview

STD878T4 from STMicroelectronics is a high-current, low-voltage NPN power transistor in DPAK (TO-252) package, rated for 5 A continuous collector current, 30 V V_CEO, and 15 W total dissipation at T_C = 25 °C; features very low V_CE(sat) (0.15 V @ IC = 6 A, IB = 0.25 A) and DC current gain h_FE ≥ 100, used as heavy-load switch in battery charger switching regulators.

For engineers reviewing the STD878T4 datasheet, STD878T4 pinout, STD878T4 application, or STD878T4 equivalent, key selection criteria include saturation voltage under high-current drive, thermal resistance (R_thJC ≤ 8.3 °C/W), junction temperature limit (150 °C), and DPAK mounting compatibility with PCB copper area for thermal management.

Technical Context

This NPN planar transistor uses "base island" layout to achieve high h_FE (>100 at IC = 500 mA) while maintaining ultra-low V_CE(sat) (0.15 V typical at IC = 6 A). Its 30 V V_CEO rating and 10 A peak collector current support robust operation in DC-DC converter primary-side switching.

Thermal design is critical: R_thJC = 8.3 °C/W enables 15 W dissipation only when case temperature is maintained at 25 °C; safe operating area (SOA) is limited by secondary breakdown at high V_CE/I_C combinations, requiring external base drive control for reliable switching.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	30 V - maximum sustainable collector-emitter voltage with base open; defines upper rail limit in low-voltage switching applications
I_C (cont.)	5 A - continuous DC collector current capability; determines usable load capacity without forced cooling
V_CE(sat)	0.15 V @ IC = 6 A, IB = 0.25 A - low conduction loss enabling >95% efficiency in high-current linear or saturated-switch modes
h_FE	≥100 @ IC = 500 mA, V_CE = 1 V - ensures sufficient current gain for direct TTL/CMOS-compatible base drive without amplification
R_thJC	8.3 °C/W - junction-to-case thermal resistance; requires heatsink or large copper pour to sustain 15 W dissipation
T_J(max)	150 °C - maximum allowable junction temperature; sets thermal derating boundary for long-term reliability
t_f	80–100 ns - fall time under resistive load (IC = 3 A); supports switching frequencies up to ~1 MHz in non-critical SMPS

Pinout & Package

DPAK (TO-252) package with exposed drain-connected tab for thermal and electrical grounding; 3-pin configuration: Pin 1 = Emitter, Pin 2 = Base, Pin 3 = Collector (tab).

Pin/Terminal	Circuit Role	Design Meaning
Pin 1	Emitter	Main current return path; connected to ground or low-side reference; soldered to PCB copper for thermal conduction
Pin 2	Base	Control input for bipolar switching; requires ~0.25 A drive current to saturate at 5–6 A collector load
Pin 3 / Tab	Collector	High-current output node; electrically and thermally tied to exposed metal tab; must be isolated from other potentials unless referenced to system ground

Key Features

Feature	Design Value
Ultra-low V_CE(sat)	0.15 V at 6 A enables <0.9 W conduction loss, reducing thermal stress in compact battery charger PCBs
High h_FE	≥100 at 500 mA allows direct microcontroller GPIO drive without buffer stage in portable equipment bias supplies
DPAK thermal performance	R_thJC = 8.3 °C/W supports 15 W dissipation with minimal heatsinking-ideal for space-constrained industrial power modules
Robust SOA	Rated for 10 A peak current (t_P < 5 ms) and 150 °C junction temperature-suited for transient-heavy battery charging cycles

Applications

Battery Charger Switching Regulator

Portable Equipment Power Management

Use Scenario: High-efficiency buck converter in 12 V/5 A Li-ion battery charger with synchronous rectification disabled.

IC Role / Device Role / Timing Role: Main NPN switch controlling energy transfer from input to output inductor; driven by PWM controller with 100 ns–1 µs edge rates.

Use Value: 0.15 V V_CE(sat) reduces conduction loss by >60% vs. standard NPN transistors, improving thermal margin and enabling smaller heatsinks.

Use Scenario: Load switch enabling/disabling 5 V rail to display backlight and audio amplifier in handheld medical monitor.

IC Role / Device Role / Timing Role: Low-loss series pass element controlled by microcontroller GPIO; operates in linear or saturated mode depending on load demand.

Use Value: h_FE ≥ 100 ensures full saturation with 5 mA base drive, eliminating need for Darlington configuration and saving board space.

Voltage Regulation in Bias Supply

Heavy Load Driver for Industrial Actuators

Use Scenario: Linear post-regulator supplying stable 3.3 V to MCU core from noisy 5 V SMPS output in factory automation controller.

IC Role / Device Role / Timing Role: Series pass transistor in emitter-follower configuration; dissipates up to 1.5 W under full 500 mA load.

Use Value: R_thJC = 8.3 °C/W allows 1.5 W dissipation with <15 °C rise above PCB copper, avoiding thermal shutdown during burst-mode operation.

Use Scenario: Driving 4 A solenoid valve in HVAC control module powered from 24 V DC bus.

IC Role / Device Role / Timing Role: High-current switch interfacing microcontroller to inductive load; includes flyback diode protection externally.

Use Value: 10 A peak current rating accommodates 3× inrush surge without degradation, ensuring 100,000-cycle mechanical reliability.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN power switching applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
STN878	SOT-223 package, lower power (1.6 W @ T_amb = 25 °C), higher R_thJA (78 °C/W)	Only suitable for low-power bias rails or signal-level switching-not for >1 A loads	Select when board space is constrained and thermal budget permits ambient-only cooling
MJD127	Higher V_CEO (80 V), lower h_FE (25–100), larger TO-220 package, R_thJC = 3 °C/W	Better for 48 V industrial systems but requires external driver due to lower gain	Choose for higher-voltage, lower-frequency applications where thermal mass outweighs footprint concerns

Compared with STN878 and MJD127, STD878T4 uniquely balances high current (5 A), ultra-low saturation voltage (0.15 V), and DPAK thermal performance (8.3 °C/W), making it optimal for compact, high-efficiency 24–30 V battery charger and portable power modules.

Availability

STD878T4 is available at Aetrix Electronics and suitable for battery charger switching regulators, portable equipment power management, and voltage regulation in bias supply circuits requiring stable component supply and legacy-design continuity.

Supply support for STD878T4 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, digital, and mixed-signal ICs and discrete devices for automotive, industrial, and consumer markets.

STD878T4 belongs to ST's high-performance bipolar power transistor product line, engineered specifically for high-current, low-voltage switching and linear regulation in portable and industrial power systems.

FAQ

Is STD878T4 RoHS-compliant and halogen-free?

Yes, STD878T4 is manufactured in ST's ECOPACK®-compliant DPAK package, meeting RoHS Directive 2011/65/EU and halogen-free requirements per IEC 61249-2-21. The device carries the "E3" marking on the package and is documented in ST's ECOPACK® database as fully compliant.

Can STD878T4 replace a MOSFET in a 5 A switching application?

STD878T4 can replace low-voltage N-channel MOSFETs only if gate drive voltage is ≥5 V and switching frequency remains below 500 kHz. Unlike MOSFETs, it requires sustained base current (~0.25 A) and exhibits slower turn-off (t_f = 80–100 ns), so it is best suited for saturated-switch or linear-regulator roles-not high-frequency synchronous rectification.

What is the recommended PCB layout for thermal management?

Use ≥25 mm² of 2-oz copper connected directly to the DPAK tab (Pin 3) with ≥4 thermal vias (0.3 mm diameter, filled or plated) to inner ground plane. Keep base and emitter traces wide (>0.5 mm) and short to minimize inductance during switching transitions.

Does STD878T4 have built-in ESD or overvoltage protection?

No, STD878T4 has no integrated ESD protection diodes or clamp structures. It relies on external components: a reverse-biased Zener (≤6 V) between base and emitter for V_EBO protection, and TVS diode across collector-emitter for inductive kick suppression in solenoid or relay driver applications.

STD878T4 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:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 5 A

Voltage - Collector Emitter Breakdown (Max):: 30 V

Vce Saturation (Max) @ Ib, Ic:: 350mV @ 50mA, 2A

Current - Collector Cutoff (Max):: 10µA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 100 @ 500mA, 1V

Power - Max:: 15 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: DPAK

STD878T4 FAQ

1.How can I place an order for STD878T4 through Aetrix?

Please submit a Request for Quotation (RFQ) for STD878T4 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 STD878T4 reliable?

The price and inventory of STD878T4 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for STD878T4 is usually 5 days.

3.What payment methods are accepted for STD878T4?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for STD878T4 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for STD878T4?

STD878T4 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your STD878T4 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 STD878T4?

For technical support, including STD878T4 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your STD878T4 requirements.

6.How does Aetrix verify that STD878T4 is sourced from the original manufacturer or authorized distributors?

All STD878T4 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 STD878T4 meets industry standards.

7.What is the process for return or replacement of STD878T4?

All STD878T4 units undergo pre-shipment inspection (PSI). If there is an issue with STD878T4, 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 STD878T4 part is unused and in its original packaging.

Return procedure for STD878T4:

1.Submit a request within 90 days.

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

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