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

STMicroelectronics BUL49DFP

Name: BUL49DFP
Brand: STMicroelectronics
SKU: BUL49DFP
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BUL49DFP

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-220-3 Full Pack

Datasheet:: BUL49DFP.pdf

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

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BUL49DFP from STMicroelectronics is a high-voltage fast-switching NPN power transistor in TO-220FP package, rated for 850 V V_CES, 5 A I_C, and 34 W P_tot at T_c ≤ 25°C. It delivers 450 V V_CEO(sus) under pulsed conditions and achieves 0.6 V V_CE(sat) at I_C = 4 A / I_B = 0.8 A, enabling use in electronic transformers for halogen lamps and low-power flyback converters.

For engineers reviewing the BUL49DFP datasheet, BUL49DFP pinout, BUL49DFP application, or BUL49DFP equivalent, this device is selected for high-ruggedness, low dynamic parameter spread, and stable switching performance in 250–300 V DC-link inductive-load SMPS topologies requiring reliable turn-off under high dV/dt.

Technical Context

This transistor employs ST's high-voltage multi-epitaxial planar process to achieve simultaneous high breakdown voltage and fast switching-evidenced by 0.6 µs storage time (t_s) and 100 ns fall time (t_f) under inductive load conditions (V_CL = 300 V, I_C = 4 A). Its ruggedness is confirmed by sustained operation at 450 V without snubber (V_CEW) and safe operating area compliance up to 150 °C junction temperature.

The TO-220FP package provides insulated mounting via plastic body (no heatsink isolation washer required), with thermal resistance R_thj-case = 3.67 °C/W and R_thj-amb = 62.5 °C/W. Electrical characteristics are specified across T_c = 25°C and T_c = 125°C, supporting design validation over full industrial temperature range.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CES	850 V - Maximum collector-emitter voltage with base open; enables direct use in 400 V AC rectified rails without derating.
I_C	5 A continuous - Sustained current handling at T_c ≤ 25°C; supports 4 A typical load in transformer-driven halogen lamp ballasts.
V_CE(sat)	0.6 V @ I_C = 4 A / I_B = 0.8 A - Low saturation voltage reduces conduction loss and thermal stress in hard-switched topologies.
t_s / t_f	0.6 µs / 100 ns (inductive load) - Fast storage/fall times minimize switching loss and enable >100 kHz operation in flyback converters.
R_thj-case	3.67 °C/W - Enables efficient heatsinking to maintain T_J ≤ 150°C at 34 W dissipation with modest copper area.
h_FE	6–60 @ I_C = 10 mA–7 A - Wide DC gain range supports both linear biasing and saturated switch operation across load conditions.

Pinout & Package

Package: TO-220FP (full-pack, insulated flange). Plastic body isolates collector (pin 2) from heatsink, eliminating need for insulating washers. Flange is electrically connected to collector terminal.

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Emission path for majority carriers	Low-impedance return node; must be routed with low-inductance layout to minimize switching overshoot.
2 (Collector)	Main high-voltage current sink	Internally bonded to insulated flange; serves as primary heat path and high-side switching node.
3 (Base)	Control electrode for carrier injection	Requires ≥0.8 A peak drive for full saturation at 4 A; sensitive to ESD due to low V_(BR)EBO = 10 V.

Key Features

Feature	Design Value
High-voltage capability	850 V V_CES rating ensures robustness against line transients in off-line SMPS with 230 V AC input.
Very high switching speed	0.6 µs storage time and 100 ns fall time reduce total switching loss below 0.5 W at 100 kHz in 300 V/4 A operation.
Low lot-to-lot parameter spread	Tight distribution of h_FE, V_CE(sat), and t_s enables consistent gate drive design across production batches.
High ruggedness	Rated for 450 V sustaining voltage without snubber and validated in reverse-biased SOA testing per Figure 12.

Applications

Electronic Transformer for Halogen Lamps

Flyback Converter (Low-Power)

Use Scenario: Step-down AC-to-AC conversion for 12 V/20–50 W halogen lighting systems using resonant or quasi-resonant topology.

IC Role / Device Role / Timing Role: Main switching transistor in self-oscillating or fixed-frequency half-bridge driver stage.

Use Value: High V_CES withstands 800 V+ ringing during zero-current switching; low t_s prevents secondary voltage collapse during dead-time.

Use Scenario: Primary-side switch in isolated 5–25 W offline flyback power supplies for consumer electronics.

IC Role / Device Role / Timing Role: Hard-switched NPN power switch driven by discrete or IC-based PWM controller.

Use Value: 0.6 V V_CE(sat) minimizes conduction loss at 4 A peak; 450 V V_CEO(sus) accommodates reflected output voltage + leakage spike margin.

Forward Converter (Single-Transistor)

DC-DC Boost Pre-regulator

Use Scenario: Single-transistor forward converter for industrial control power modules requiring 12–24 V outputs at ≤15 W.

IC Role / Device Role / Timing Role: Primary-side main switch synchronized with reset winding and freewheeling diode.

Use Value: Ruggedness supports repeated avalanche stress during core reset; 150 °C T_J(max) allows compact heatsink design in sealed enclosures.

Use Scenario: Boost switch in universal-input PFC front-end or battery-powered DC-DC pre-regulators stepping 12 V to 400 V.

IC Role / Device Role / Timing Role: High-voltage switching element in discontinuous conduction mode (DCM) boost stage.

Use Value: 850 V V_CES eliminates need for series-connected devices; low dynamic parameter spread ensures predictable duty cycle limits.

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
STBUL49D	Same die, TO-220 (non-insulated flange); R_thj-case = 1.56 °C/W but requires insulating pad for heatsink mounting.	Preferred where thermal performance is critical and mechanical isolation can be implemented externally.	Select when board space permits external insulation and lower thermal resistance is prioritized over assembly simplicity.
BU508AF	Lower V_CES = 700 V; higher V_CE(sat) = 1.2 V @ 4 A; slower t_f = 250 ns; same TO-220FP package.	Suitable only for 230 V AC-derived rails with tight snubber design; not recommended for 400 V DC-link applications.	Choose only if cost sensitivity outweighs voltage margin and switching loss requirements.

Compared with STBUL49D and BU508AF, BUL49DFP uniquely combines 850 V blocking, TO-220FP insulation, and sub-microsecond switching-making it optimal for compact, high-reliability halogen transformer and low-power flyback designs where safety, thermal management, and efficiency are co-constrained.

Availability

BUL49DFP is available at Aetrix Electronics and suitable for electronic transformers for halogen lamps, flyback converters, and forward converters requiring stable component supply with guaranteed long-term availability and traceable sourcing.

Supply support for BUL49DFP 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 industrial, automotive, and consumer markets.

BUL49DFP belongs to ST's high-voltage power transistor product line, engineered specifically for rugged, high-efficiency switching in off-line lighting and low-power SMPS applications where reliability under repetitive transient stress is essential.

FAQ

Is BUL49DFP RoHS-compliant and lead-free?

Yes. BUL49DFP is manufactured in ST's ECOPACK®-compliant TO-220FP package with lead-free second-level interconnect, meeting JEDEC JESD97 standards. The inner box label indicates lead-free status and maximum soldering temperature ratings per JEDEC specifications.

What is the maximum safe operating frequency for BUL49DFP in a flyback converter?

Based on measured t_s = 0.6 µs and t_f = 100 ns under inductive load, BUL49DFP supports stable operation up to 150 kHz in flyback topologies with proper gate drive strength (≥0.8 A peak) and snubber optimization. Above 120 kHz, switching loss increases nonlinearly due to tail current effects.

Can BUL49DFP replace BU2508AX in existing halogen lamp transformer designs?

No. BU2508AX has V_CES = 1500 V and different gain/saturation characteristics. BUL49DFP's 850 V rating is insufficient for BU2508AX's intended 1 kV+ applications. Substitution requires full revalidation of SOA, thermal margin, and EMI behavior-especially under no-load and short-circuit conditions.

Does BUL49DFP require a base resistor for safe operation?

Yes. A base resistor is mandatory to limit I_B to ≤2 A DC and ≤4 A peak. For 4 A I_C saturation, minimum I_B = 0.8 A implies R_B ≤ (V_drive − 1.3 V) / 0.8 A. Typical value is 10 Ω for 5 V TTL drive, ensuring h_FE-independent saturation and preventing secondary breakdown.

BUL49DFP 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):: 5 A

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

Vce Saturation (Max) @ Ib, Ic:: 1.2V @ 800mA, 4A

Current - Collector Cutoff (Max):: 100µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 4 @ 7A, 10V

Power - Max:: 34 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220FP

BUL49DFP FAQ

1.How can I place an order for BUL49DFP through Aetrix?

Please submit a Request for Quotation (RFQ) for BUL49DFP 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 BUL49DFP reliable?

The price and inventory of BUL49DFP are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BUL49DFP is usually 5 days.

3.What payment methods are accepted for BUL49DFP?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BUL49DFP transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BUL49DFP?

BUL49DFP orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BUL49DFP 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 BUL49DFP?

For technical support, including BUL49DFP datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BUL49DFP requirements.

6.How does Aetrix verify that BUL49DFP is sourced from the original manufacturer or authorized distributors?

All BUL49DFP 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 BUL49DFP meets industry standards.

7.What is the process for return or replacement of BUL49DFP?

All BUL49DFP units undergo pre-shipment inspection (PSI). If there is an issue with BUL49DFP, 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 BUL49DFP part is unused and in its original packaging.

Return procedure for BUL49DFP:

1.Submit a request within 90 days.

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

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