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

STMicroelectronics BUL742CFP

Name: BUL742CFP
Brand: STMicroelectronics
SKU: BUL742CFP
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BUL742CFP

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-220-3 Full Pack

Datasheet:: BUL742CFP.pdf

Description:: TRANS NPN 400V 4A TO-220FP

Quantity:: RFQ Add To RFQ list

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Inventory:8,379

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Product details

Overview

BUL742CFP from STMicroelectronics is a high-voltage fast-switching NPN power transistor in TO-220FP package, rated for V_CEO = 400 V, I_C = 4 A, and V_CES = 1050 V, with t_s = 2.4–3.5 µs storage time and R_thJC = 4.17 °C/W, designed for electronic ballasts and switch-mode power supplies operating under high-repetition avalanche stress.

For engineers reviewing the BUL742CFP datasheet, BUL742CFP pinout, BUL742CFP application, or BUL742CFP equivalent, key selection criteria include ruggedness under repetitive avalanche (E_AR = 6 mJ), low V_CE(sat) at high current (0.5 V @ 3.5 A), and isolation withstand voltage (V_ISO = 1500 V RMS) for heatsink-mounted operation.

Technical Context

This device uses high-voltage multi-epitaxial planar technology to achieve both high breakdown voltage and fast switching. Its intrinsic ruggedness-enabled by an increased intermediate layer-allows safe operation at high collector current during breakdown without external Transil protection, unlike conventional lamp-ballast converters.

The TO-220FP variant features insulated tab (V_ISO = 1500 V RMS), making it suitable for direct mounting on grounded heatsinks. Thermal resistance junction-to-case is 4.17 °C/W, significantly higher than TO-220 (1.79 °C/W), reflecting its plastic-isolated construction and lower power dissipation limit (30 W vs. 70 W).

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	400 V - Sustains 400 V collector-emitter voltage with base open, defining safe linear/switching operation in SMPS primary-side circuits.
V_CES	1050 V - Withstands 1050 V with base shorted to emitter, enabling robustness against voltage transients in flyback and resonant topologies.
I_C	4 A continuous - Supports sustained output power up to ~1.2 kW in hard-switched converters before thermal derating applies.
t_s	2.4–3.5 µs - Short storage time enables high-frequency switching (>50 kHz) with minimal switching loss in ballast drivers.
E_AR	6 mJ - Repetitive avalanche energy rating allows reliable operation under inductive turn-off stress without snubber networks.
R_thJC	4.17 °C/W - Junction-to-case thermal resistance confirms need for active heatsinking when dissipating >15 W continuously.
V_ISO	1500 V RMS - Isolation voltage between all three leads and external heatsink permits safe direct-mounting on conductive chassis grounds.

Pinout & Package

Package: TO-220FP - Full-molded plastic package with electrically insulated metal tab (no internal metal connection to collector), enabling direct heatsink mounting without insulating washers.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Current sink terminal	Low-impedance path for full load current; connected to ground or low-side return in half-bridge and flyback configurations.
2 (Base)	Control input	Receives drive current (I_B ≤ 2 A) to saturate or cut off; requires careful gate driver matching due to h_FE variation (25–100).
3 (Collector)	High-voltage power input	Connected to primary winding or DC bus; handles up to 1050 V transient spikes and 4 A continuous conduction.
TAB (Isolated)	Heatsink interface	Electrically isolated metal surface rated for 1500 V RMS; mounts directly to grounded heatsink without thermal pad or insulator.

Key Features

Feature	Design Value
High-voltage capability	V_CES = 1050 V enables use in universal-input offline SMPS and high-bus industrial converters without cascaded devices.
Rugged avalanche performance	E_AR = 6 mJ allows repeated inductive turn-off without degradation-critical for lamp-ballast reliability over 10,000+ hours.
Low dynamic parameter spread	Tight lot-to-lot consistency in t_s, V_CE(sat), and h_FE reduces need for system-level trimming in mass-produced lighting gear.
Insulated tab packaging	TO-220FP's 1500 V RMS isolation eliminates creepage/clearance concerns and simplifies mechanical assembly in compact ballast PCBs.

Applications

Electronic Ballast for Fluorescent Lamps

Offline Switch-Mode Power Supply

Use Scenario: Driving resonant LC tank in instant-start fluorescent lamp ballasts operating at 20–60 kHz.

IC Role / Device Role / Timing Role: High-voltage NPN switch controlling lamp current via half-bridge topology; timing governed by external oscillator and feedback loop.

Use Value: Intrinsic avalanche ruggedness eliminates need for external Transil clamping, reducing BOM count and board area by ~15%.

Use Scenario: Primary-side switch in 30–100 W universal-input flyback converters for industrial control power rails.

IC Role / Device Role / Timing Role: Main power switch turning on/off at fixed frequency (40–130 kHz); duty cycle modulated by optocoupler feedback.

Use Value: V_CES = 1050 V supports direct rectified AC line operation without voltage doublers, improving efficiency by 2–3%.

DC-DC Converter for LED Drivers

Induction Heating Half-Bridge

Use Scenario: Step-down switching element in constant-current LED drivers powering high-bay luminaires (100–200 W).

IC Role / Device Role / Timing Role: Low-side switch in buck topology; driven by PWM controller with current-sense feedback.

Use Value: R_thJC = 4.17 °C/W and V_CE(sat) = 0.5 V @ 3.5 A enable thermally stable operation at 85°C ambient without forced air cooling.

Use Scenario: Upper-leg switch in 20–50 kHz resonant half-bridge for domestic induction cooktops.

IC Role / Device Role / Timing Role: High-side switching device synchronized with complementary low-side MOSFET; commutation controlled by dead-time logic.

Use Value: 1500 V RMS isolation allows direct mounting on shared heatsink with low-side device, reducing thermal interface complexity and cost.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
STBUL742C	Same die, TO-220 package (non-isolated tab); R_thJC = 1.79 °C/W; V_ISO not rated.	Requires insulating washer for heatsink mounting; unsuitable where chassis grounding mandates isolation.	Select when thermal budget allows higher power dissipation and mechanical isolation is handled externally.
BU508AF	V_CEO = 1000 V, I_C = 8 A, but slower switching (t_s ≈ 5 µs); no specified E_AR rating.	Lacks documented avalanche ruggedness; needs external clamping in inductive loads.	Choose only for non-avalanche, low-frequency (<20 kHz) applications where peak current dominates over switching loss.

Compared with STBUL742C and BU508AF, BUL742CFP uniquely combines certified 1500 V isolation, 6 mJ repetitive avalanche rating, and sub-4 µs storage time-making it the only drop-in solution for compact, high-reliability fluorescent ballasts requiring zero external protection.

Availability

BUL742CFP is available at Aetrix Electronics and suitable for electronic ballasts, offline switch-mode power supplies, LED drivers, and induction heating systems requiring stable component supply across extended production lifecycles.

Supply support for BUL742CFP 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 power devices for industrial, automotive, and consumer markets.

The BUL742CFP belongs to ST's high-voltage bipolar transistor family, engineered specifically for rugged, high-frequency switching in lighting and power conversion where reliability under repetitive avalanche stress is mandatory.

FAQ

What is the maximum allowable case temperature for continuous operation?

The maximum operating junction temperature is 150 °C. With R_thJC = 4.17 °C/W and P_TOT = 30 W, the case temperature must remain ≤ 20.5 °C above ambient to avoid exceeding T_J. In practice, derating begins at T_C > 80 °C per Figure 4, limiting usable power to ~12 W at 100 °C case temperature.

Can BUL742CFP replace BUL742C in existing TO-220 designs?

No direct replacement: BUL742CFP has insulated tab (TO-220FP), while BUL742C uses standard TO-220 with electrically connected tab. Mechanical mounting differs, and thermal resistance is higher (4.17 vs. 1.79 °C/W). Electrical specs match, but layout and heatsink interface must be redesigned.

Does BUL742CFP require a base resistor for safe switching?

Yes. With h_FE ranging from 25 to 100, a base resistor must ensure I_B ≥ I_C/h_FE(min) for saturation. For 4 A collector current, minimum I_B = 160 mA (using h_FE = 25). A 33 Ω resistor with 5.5 V drive delivers ~167 mA, ensuring robust saturation while limiting peak base current to <2 A.

Is BUL742CFP compliant with RoHS and REACH regulations?

Yes. Per ST's ECOPACK® documentation (Doc ID 9488 Rev 4), BUL742CFP is manufactured in RoHS-compliant, halogen-free packaging. It meets EU Directive 2011/65/EU and Regulation (EC) No. 1907/2006 (REACH), with full material declarations available through ST's product portal.

BUL742CFP Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-220-3 Full Pack

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: NPN

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

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

Vce Saturation (Max) @ Ib, Ic:: 1.5V @ 1A, 3.5A

Current - Collector Cutoff (Max):: 250µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 48 @ 100mA, 5V

Power - Max:: 30 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220FP

BUL742CFP FAQ

1.How can I place an order for BUL742CFP through Aetrix?

Please submit a Request for Quotation (RFQ) for BUL742CFP 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 BUL742CFP reliable?

The price and inventory of BUL742CFP are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BUL742CFP is usually 5 days.

3.What payment methods are accepted for BUL742CFP?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BUL742CFP transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BUL742CFP?

BUL742CFP orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BUL742CFP 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 BUL742CFP?

For technical support, including BUL742CFP datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BUL742CFP requirements.

6.How does Aetrix verify that BUL742CFP is sourced from the original manufacturer or authorized distributors?

All BUL742CFP 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 BUL742CFP meets industry standards.

7.What is the process for return or replacement of BUL742CFP?

All BUL742CFP units undergo pre-shipment inspection (PSI). If there is an issue with BUL742CFP, 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 BUL742CFP part is unused and in its original packaging.

Return procedure for BUL742CFP:

1.Submit a request within 90 days.

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

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