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

STMicroelectronics BULB742C-1

Name: BULB742C-1
Brand: STMicroelectronics
SKU: BULB742C-1
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BULB742C-1

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-262-3 Long Leads, I2PAK, TO-262AA

Datasheet:: BULB742C-1.pdf

Description:: TRANS NPN 400V 4A I2PAK

Quantity:: RFQ Add To RFQ list

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Inventory:1,000

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Product details

Overview

BULB742C-1 from STMicroelectronics is a high-voltage fast-switching NPN power transistor in I²PAK (TO-262) package, rated for V_CES = 1050 V, I_C = 4 A, and P_TOT = 70 W at T_C = 25 °C. It delivers very high switching speed (t_s = 2.4–3.5 µs, t_f = 350–500 ns), intrinsic ruggedness against repetitive avalanche (E_ar = 6 mJ), and operates up to T_J = 150 °C - designed specifically for electronic ballasts in fluorescent lighting systems.

For engineers reviewing the BULB742C-1 datasheet, BULB742C-1 pinout, BULB742C-1 application, or BULB742C-1 equivalent, key selection criteria include its 1050 V collector-emitter blocking voltage, low V_CE(sat) (0.15 V @ 1 A), high dV/dt capability, ruggedness without external Transil protection, and thermal resistance R_thJC = 1.79 °C/W in I²PAK.

Technical Context

This transistor uses high-voltage multi-epitaxial planar technology with an increased intermediate layer to enhance breakdown robustness and sustain high collector current during transient overvoltage events. Its design eliminates the need for external Transil clamping in lamp ballast converters.

It supports resistive-load switching with h_FE = 25–100 (tested at V_CE = 3–5 V), exhibits low leakage (I_CES ≤ 10 µA @ V_CE = 1050 V), and maintains stable dynamic parameters across production lots - critical for consistent performance in high-reliability SMPS and ballast control stages.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CES	1050 V - Enables direct operation across rectified 800 V DC bus in high-line SMPS and electronic ballasts.
I_C	4 A continuous - Supports lamp drive currents up to 3.5 A with margin for surge handling.
P_TOT	70 W @ T_C = 25 °C - Delivers high power density in I²PAK with R_thJC = 1.79 °C/W.
t_s/t_f	2.4 µs / 350 ns - Enables >100 kHz switching in resonant ballast topologies with minimal switching loss.
E_ar	6 mJ - Withstands repetitive avalanche energy without degradation, removing need for external snubbers or Transils.
V_CE(sat)	0.15 V @ I_C = 1 A, I_B = 0.2 A - Reduces conduction loss and self-heating in high-duty-cycle operation.
R_thJC	1.79 °C/W - Allows efficient heatsink coupling in compact I²PAK-based lamp driver PCB layouts.

Pinout & Package

The BULB742C-1 is housed in an I²PAK (TO-262) thermally enhanced surface-mount package with isolated tab (pin 3). The case is electrically connected to the collector, enabling direct mounting to heatsinks without insulating washers when isolation is not required.

Pin/Terminal	Circuit Role	Design Meaning
1	Base	Low-impedance control input requiring ±4 A peak drive for fast turn-on/turn-off.
2	Emitter	Reference node for gate drive and current sensing; tied to source/common rail in half-bridge configurations.
3 (TAB)	Collector	High-voltage power output terminal; electrically connected to metal tab for direct heatsink attachment.

Key Features

Feature	Design Value
High-voltage blocking	V_CES = 1050 V enables use in universal-input 85–265 V AC ballasts without voltage doublers.
Intrinsic avalanche ruggedness	6 mJ repetitive avalanche energy rating allows safe operation under inductive switching stress without external protection.
Low spread of dynamic parameters	Tight lot-to-lot consistency in t_s, t_f, and h_FE ensures predictable timing and gain in mass-produced lighting controllers.
Fast switching speed	Sub-microsecond fall time (350 ns) minimizes overlap loss in high-frequency resonant inverters.

Applications

Fluorescent Lamp Electronic Ballast

High-Voltage SMPS Primary Switch

Use Scenario: Driving resonant LC tank in 20–60 W instant-start fluorescent fixtures operating from 220–240 V AC mains.

IC Role / Device Role / Timing Role: High-side NPN switch in half-bridge inverter stage; commutated at 30–70 kHz.

Use Value: Eliminates external Transil due to intrinsic avalanche ruggedness, reducing BOM count and board space by 2 components.

Use Scenario: Primary-side switching element in 50–100 W offline flyback or forward converter for industrial control power supplies.

IC Role / Device Role / Timing Role: Main power switch handling rectified 375–400 V DC bus with duty cycle modulation.

Use Value: 1050 V V_CES provides 2× safety margin over 400 V DC bus, improving long-term reliability under line surges.

LED Driver Power Stage

Induction Heating Half-Bridge

Use Scenario: Constant-current switching regulator for high-bay LED luminaires powered from 347 V AC commercial lines.

IC Role / Device Role / Timing Role: Series-pass switch regulating LED string current via PWM dimming at 1–20 kHz.

Use Value: Low V_CE(sat) (0.15 V) reduces conduction loss at 2–4 A, improving efficiency above 92%.

Use Scenario: Low-side switch in 20–50 kHz resonant half-bridge driving induction cooktop coils.

IC Role / Device Role / Timing Role: Fast-turnoff NPN switch synchronized with complementary high-side device.

Use Value: 350 ns fall time limits switching loss during zero-voltage switching transitions, maintaining thermal stability.

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
STW12NK90Z	900 V, 12 A MOSFET; R_DS(on) = 0.7 Ω; gate-driven, no base current needed.	Lower switching loss at >100 kHz but higher conduction loss above 3 A; requires level-shifting gate drive.	Prefer for higher-frequency (>150 kHz), lower-power (<50 W) ballasts where gate drive complexity is acceptable.
BUL128D	1000 V, 4 A NPN; slower (t_f = 1.2 µs); no specified E_ar; TO-220 only.	Lacks avalanche ruggedness; requires external Transil in ballast designs; limited to <50 kHz operation.	Select only for cost-sensitive, non-ruggedized 50 Hz–40 kHz linear or quasi-resonant ballasts with proven snubber design.

Compared with STW12NK90Z and BUL128D, the BULB742C-1 uniquely combines 1050 V blocking, sub-microsecond switching, and 6 mJ avalanche energy in I²PAK - making it optimal for compact, high-reliability fluorescent ballasts where protection simplicity and thermal performance are critical.

Availability

BULB742C-1 is available at Aetrix Electronics and suitable for electronic ballasts, high-voltage switch-mode power supplies, LED drivers, and induction heating power stages requiring stable component supply and long-lifecycle support.

Supply support for BULB742C-1 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, microcontroller, power, and sensor solutions for industrial, automotive, and consumer markets.

The BUL742C/BULB742C family belongs to ST's high-voltage power transistor product line, engineered specifically for rugged, high-efficiency lighting and power conversion applications demanding reliable operation at >1000 V and >100 kHz.

FAQ

Is BULB742C-1 pin-compatible with BUL742C in TO-220?

No - BULB742C-1 uses I²PAK (TO-262) with 3-pin layout (Base–Emitter–Collector TAB), while BUL742C in TO-220 has identical pin order but different mechanical footprint and thermal interface. PCB layout and heatsink mounting must be redesigned for I²PAK.

Does BULB742C-1 require a Transil diode in fluorescent ballast designs?

No - its intrinsic 6 mJ repetitive avalanche energy rating and rugged construction eliminate the need for external Transil clamping in standard electronic ballast topologies, as confirmed in ST's application note AN2341 and Figure 14 (Reverse biased SOA).

What is the maximum recommended case temperature for continuous operation?

The absolute maximum junction temperature is 150 °C. With R_thJC = 1.79 °C/W, sustained operation at full 70 W dissipation requires case temperature ≤ 25 °C. For 60 °C case, derated power is ~45 W per Figure 4 (Derating curve).

Can BULB742C-1 be used in avalanche mode intentionally?

Yes - ST specifies E_ar = 6 mJ under defined test conditions (L = 2 mH, C = 1.8 nF, V_BE(off) = −5 V). Intentional avalanche operation is supported for energy recovery or snubberless designs, provided pulse width, repetition rate, and thermal limits are strictly observed.

BULB742C-1 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-262-3 Long Leads, I2PAK, TO-262AA

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:: 25 @ 800mA, 3V

Power - Max:: 70 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-262 (I2PAK)

BULB742C-1 FAQ

1.How can I place an order for BULB742C-1 through Aetrix?

Please submit a Request for Quotation (RFQ) for BULB742C-1 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 BULB742C-1 reliable?

The price and inventory of BULB742C-1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BULB742C-1 is usually 5 days.

3.What payment methods are accepted for BULB742C-1?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BULB742C-1 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BULB742C-1?

BULB742C-1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BULB742C-1 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 BULB742C-1?

For technical support, including BULB742C-1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BULB742C-1 requirements.

6.How does Aetrix verify that BULB742C-1 is sourced from the original manufacturer or authorized distributors?

All BULB742C-1 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 BULB742C-1 meets industry standards.

7.What is the process for return or replacement of BULB742C-1?

All BULB742C-1 units undergo pre-shipment inspection (PSI). If there is an issue with BULB742C-1, 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 BULB742C-1 part is unused and in its original packaging.

Return procedure for BULB742C-1:

1.Submit a request within 90 days.

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

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