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

STMicroelectronics BUL38D

Name: BUL38D
Brand: STMicroelectronics
SKU: BUL38D
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BUL38D

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-220-3

Datasheet:: BUL38D.pdf

Description:: TRANS NPN 450V 5A TO-220

Quantity:: RFQ Add To RFQ list

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Inventory:1,881

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Product details

Overview

BUL38D from STMicroelectronics is a high-voltage fast-switching NPN power transistor in TO-220 package, rated for V_CEO = 450 V, I_C = 5 A, and P_tot = 80 W at T_c ≤ 25 °C, with integrated antiparallel collector-emitter diode and characterized up to 125 °C junction temperature. It is designed specifically for electronic transformers in halogen lamp ballasts and switch-mode power supplies requiring rugged high-voltage switching.

For engineers reviewing the BUL38D datasheet, BUL38D pinout, BUL38D application, or BUL38D equivalent, key selection criteria include its 450 V V_CEO, 1.56 °C/W R_thJC, 1 µs storage time (resistive load), integrated diode (V_F = 1.5 V @ 2 A), and group-A/B h_FE binning (10–60) for consistent gain control in lighting and SMPS designs.

Technical Context

The BUL38D employs high-voltage multi-epitaxial planar technology to achieve high-speed switching with low dynamic parameter spread across production lots. Its internal structure includes an integrated antiparallel collector-emitter diode, enabling self-commutated operation without external flyback diodes in inductive loads.

It is fully characterized at 125 °C - including V_CE(sat), h_FE, t_s, and t_f - supporting reliable thermal design in enclosed lighting and power supply environments. The device's safe operating area (SOA) and reverse-biased SOA curves are explicitly defined for both resistive and inductive switching conditions.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	450 V - maximum collector-emitter voltage with base open, defining primary breakdown margin in SMPS and electronic transformer topologies
I_C	5 A continuous - steady-state current handling capability at case temperature ≤25 °C, suitable for 50–100 W halogen lamp drivers
P_tot	80 W - total power dissipation limit at T_c = 25 °C, requiring heatsinking for sustained operation above ~25 W
R_thJC	1.56 °C/W - junction-to-case thermal resistance, enabling precise thermal modeling when mounted on standard TO-220 heatsinks
t_s (resistive)	1 µs - storage time under V_CC = 150 V, I_C = 2.5 A, defining minimum off-time for 500 kHz+ switching in compact electronic transformers
V_F (diode)	1.5 V @ 2 A - forward voltage of integrated antiparallel diode, reducing component count and PCB space in flyback and resonant converters
h_FE range	Group A: 10–22, Group B: 23–60 - pre-selected DC current gain bins ensuring predictable base drive requirements across production lots

Pinout & Package

Package: TO-220 (3-pin, straight lead, insulated tab). Pin 1 = emitter, Pin 2 = base, Pin 3 = collector (tab-connected). Mounting tab is electrically connected to collector and thermally coupled to junction via low-R_thJC path.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (Emitter)	Current return path for main conduction	Low-inductance emitter connection supports fast turn-on/turn-off; referenced to ground in common-emitter configurations
Pin 2 (Base)	Control input for bipolar conduction	Requires active drive (0.2–0.75 A peak) for full saturation; sensitive to ESD due to low V_EBO = 9 V
Pin 3 (Collector / Tab)	Main high-voltage output terminal and thermal interface	Collector tied directly to metal tab; requires insulating washer when mounted to grounded heatsink; enables direct thermal coupling to heatsink

Key Features

Feature	Design Value
Integrated antiparallel diode	Eliminates need for external flyback diode in inductive switching applications, reducing BOM count and layout complexity
125 °C full characterization	Guarantees electrical parameters (V_CE(sat), t_s, h_FE) remain within spec at elevated case temperatures common in enclosed lamp transformers
Low lot-to-lot dynamic spread	Ensures consistent switching timing (t_s, t_f) across manufacturing batches, critical for EMI-controlled lighting systems
High ruggedness rating	Validated for repetitive avalanche and SOA compliance under inductive switching stress, improving field reliability in halogen lamp replacements
ECOPACK® compliant packaging	Meets RoHS and halogen-free requirements per ST's environmental standards, supporting global regulatory compliance for consumer lighting

Applications

Electronic Transformer for Halogen Lamps

Switch-Mode Power Supply

Use Scenario: High-frequency AC-AC conversion (20–50 kHz) to drive 12 V halogen lamps from mains input via resonant half-bridge topology.

IC Role / Device Role / Timing Role: Main switching transistor in half-bridge leg, handling 450 V blocking and 2–3 A peak current during resonant transitions.

Use Value: Integrated diode enables self-commutation during dead-time, eliminating external diode and reducing transformer leakage-induced voltage spikes.

Use Scenario: Primary-side switch in offline flyback or forward converters delivering 30–60 W for industrial auxiliary supplies.

IC Role / Device Role / Timing Role: High-voltage NPN switch controlling energy transfer from primary winding, operating at 50–100 kHz with hard-switched or quasi-resonant gate drive.

Use Value: 1.56 °C/W R_thJC and 80 W P_tot allow stable operation with minimal heatsink in compact enclosures, while 1 µs t_s supports efficient high-frequency operation.

Inductive Ballast Replacement

DC-DC Converter for LED Drivers

Use Scenario: Solid-state replacement of magnetic inductive ballasts in commercial track lighting systems.

IC Role / Device Role / Timing Role: Fast-switching power transistor in self-oscillating or externally clocked resonant driver, sustaining 450 V transients during lamp ignition.

Use Value: Guaranteed V_CEO(sus) = 450 V and rugged SOA ensure reliable ignition surge handling without snubber circuits.

Use Scenario: High-side switch in isolated DC-DC stage powering constant-current LED modules from 24–48 V bus.

IC Role / Device Role / Timing Role: Primary-side switch in flyback converter, providing galvanic isolation and precise output regulation for LED strings.

Use Value: Pre-selected h_FE groups (A/B) enable consistent base drive design across production, minimizing LED current variation in mass-produced luminaires.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
STBUL74	V_CEO = 700 V, I_C = 8 A, R_thJC = 1.25 °C/W, no integrated diode	Higher voltage margin but requires external flyback diode; better suited for >100 W SMPS with higher transient stress	Select when system-level V_CL exceeds 450 V or when higher current headroom is needed without diode integration
BUL49D	V_CEO = 450 V, I_C = 10 A, P_tot = 125 W, same TO-220 package and integrated diode	Higher current/power rating; identical pinout and diode function but larger thermal footprint required	Choose for upgraded 100–150 W halogen transformer designs where BUL38D approaches thermal limits

Compared with STBUL74 and BUL49D, the BUL38D offers optimal balance of voltage rating, integrated diode, and thermal efficiency for 30–80 W halogen lamp drivers - where STBUL74 adds unnecessary voltage overhead and BUL49D increases cost and heatsink size without proportional benefit.

Availability

BUL38D is available at Aetrix Electronics and suitable for electronic transformers for halogen lamps, switch-mode power supplies, inductive ballast replacements, and DC-DC converters for LED drivers requiring stable component supply and long-term manufacturability.

Supply support for BUL38D 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, discrete devices, and MEMS sensors for automotive, industrial, and consumer markets.

The BUL38D belongs to ST's high-voltage power transistor product line, engineered specifically for energy-efficient, compact lighting and power conversion systems where ruggedness, thermal stability, and integrated functionality are critical.

FAQ

Is the BUL38D pin-compatible with other TO-220 NPN transistors like the BU508A?

No - while both use TO-220 packages, the BUL38D has emitter-base-collector pinout (1-2-3), whereas BU508A uses emitter-collector-base (1-3-2). Incorrect mounting causes immediate failure. Always verify pin assignment using Figure 1 in ST's Doc ID 7176 before PCB layout or assembly.

Does the integrated diode support bidirectional current flow in bridge configurations?

No - the integrated diode is unidirectional (anode at collector, cathode at emitter) and only conducts during flyback or freewheeling phases. It does not enable true bidirectional switching; for H-bridge or synchronous rectification, external diodes or MOSFETs are required.

What is the maximum recommended case temperature for continuous operation?

The absolute maximum junction temperature is 150 °C, and the device is fully characterized up to T_c = 125 °C. For reliable 10+ year operation in lighting applications, ST recommends limiting T_c to ≤90 °C using appropriate heatsinking, based on derating curves in Figure 3 of Doc ID 7176.

How does group-A vs. group-B h_FE affect base drive design?

Group A (h_FE = 10–22) requires higher base current (e.g., 0.4–0.75 A for I_C = 3 A), while Group B (23–60) allows lower drive (e.g., 0.2–0.4 A). Designers must size base drive circuitry to accommodate the worst-case group - typically Group A - unless ST confirms shipment of a specific group for the order.

BUL38D Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-220-3

Packaging:: Tube

Product Status:: Active

Transistor Type:: NPN

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

Voltage - Collector Emitter Breakdown (Max):: 450 V

Vce Saturation (Max) @ Ib, Ic:: 1.1V @ 750mA, 3A

Current - Collector Cutoff (Max):: 250µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 10 @ 10mA, 5V

Power - Max:: 80 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220

BUL38D FAQ

1.How can I place an order for BUL38D through Aetrix?

Please submit a Request for Quotation (RFQ) for BUL38D 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 BUL38D reliable?

The price and inventory of BUL38D are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BUL38D is usually 5 days.

3.What payment methods are accepted for BUL38D?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BUL38D transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BUL38D?

BUL38D orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BUL38D 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 BUL38D?

For technical support, including BUL38D datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BUL38D requirements.

6.How does Aetrix verify that BUL38D is sourced from the original manufacturer or authorized distributors?

All BUL38D 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 BUL38D meets industry standards.

7.What is the process for return or replacement of BUL38D?

All BUL38D units undergo pre-shipment inspection (PSI). If there is an issue with BUL38D, 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 BUL38D part is unused and in its original packaging.

Return procedure for BUL38D:

1.Submit a request within 90 days.

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

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