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

STMicroelectronics STL73D

Name: STL73D
Brand: STMicroelectronics
SKU: STL73D
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: STL73D

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-226-3, TO-92-3 (TO-226AA)

Datasheet:: STL73D.pdf

Description:: TRANS NPN 400V 1.5A TO-92-3

Quantity:: RFQ Add To RFQ list

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Inventory:3,276

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Product details

Overview

STL73D from STMicroelectronics is a high-voltage fast-switching NPN power transistor with 700 V V_CES, 1.5 A I_C, and 1 µs rise time, featuring an integrated antiparallel collector-emitter diode. It is designed for electronic ballasts in compact fluorescent lamps, operating reliably up to 150 °C junction temperature.

For engineers reviewing the STL73D datasheet, STL73D pinout, STL73D application, or STL73D equivalent, key selection criteria include V_CEO(sus) = 400 V, t_r/t_f ≤ 1/0.7 µs, V_CE(sat) ≤ 0.4 V at 1 A, integrated diode forward voltage of 1.5 V, and TO-92 package thermal resistance of 83 °C/W.

Technical Context

The STL73D employs high-voltage multi-epitaxial planar technology with cellular emitter structure and planar edge termination to simultaneously achieve high RBSOA and fast switching. Its integrated antiparallel diode enables self-commutated operation in inductive ballast circuits without external flyback components.

It is characterized for resistive and inductive load switching (L = 3 mH), with specified storage time of 0.3 µs under inductive conditions and V_CE(sat) tested at multiple current/base drive points (0.3–1 A / 60–250 mA), confirming stable gain across operating range.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CES	700 V - supports direct mains-connected ballast topologies without intermediate step-down
I_C	1.5 A continuous - sufficient for 20–40 W CFL lamp drive with margin
t_r/t_f	1 µs / 0.7 µs - enables >50 kHz switching in resonant lamp ignition circuits
V_CE(sat)	0.4 V at I_C = 1 A, I_B = 250 mA - minimizes conduction loss in high-duty-cycle operation
R_thJC	83 °C/W - defines thermal derating limit for TO-92 mounting on PCB without heatsink
V_F (diode)	1.5 V at I_F = 0.5 A - provides low-loss freewheeling path during inductive turn-off
h_FE group	L (10–16) or H (15–21) - ensures predictable base drive requirements across production lots

Pinout & Package

STL73D is housed in a standard TO-92 plastic package (JEDEC TO-92 variant), with lead finish compliant with ECOPACK® environmental specifications. Mechanical dimensions conform to ST's documented bulk and ammopack variants (Doc ID 15147 Rev 2, pp. 5–7).

Pin/Terminal	Circuit Role	Design Meaning
E (Emitter)	Current sink terminal, referenced to ground in common-emitter ballast drivers	Low-inductance connection point for return path; rated for 1.5 A continuous, 3 A peak
B (Base)	Control input for bipolar switching	Requires 250 mA peak drive for full saturation at 1 A collector current
C (Collector)	High-voltage output node connected to lamp resonant tank	Withstands 700 V blocking; integrates antiparallel diode cathode internally

Key Features

Feature	Design Value
Integrated antiparallel diode	Eliminates need for external flyback diode in CFL half-bridge ballasts, reducing BOM count and layout area
Cellular emitter + planar edge termination	Enables simultaneous high RBSOA and sub-microsecond switching, critical for reliable lamp ignition
Low V_CE(sat) at high I_C	0.4 V @ 1 A reduces conduction loss by >30% vs. legacy 0.6 V devices, improving thermal margin
h_FE grouping (L/H)	Guarantees consistent base drive design across production batches without recalibration
ECOPACK® compliance	Meets RoHS and halogen-free requirements for lighting products sold in EU and global markets

Applications

Compact Fluorescent Lamp (CFL) Ballast

LED Driver with Boost PFC Stage

Use Scenario: High-frequency resonant inverter driving 20–40 W twin-tube CFLs directly from rectified AC line.

IC Role / Device Role / Timing Role: Main switching transistor in half-bridge topology; handles 40–70 kHz switching with integrated diode freewheeling.

Use Value: Enables compact, low-cost ballast designs with <10 ms lamp start time and >10,000-hour lifetime due to low switching loss and robust SOA.

Use Scenario: Primary-side switch in discontinuous conduction mode (DCM) boost PFC stage for 15–25 W LED luminaires.

IC Role / Device Role / Timing Role: High-voltage switch handling 400 V DC link; operates at 50–100 kHz with controlled dV/dt via integrated diode recovery.

Use Value: Reduces EMI filter size by 25% compared to discrete diode solutions due to matched diode recovery characteristics and lower reverse recovery charge.

Inductive Load Snubberless Switching

AC-DC Adapter Auxiliary Supply

Use Scenario: Direct switching of relay coils or solenoids rated up to 300 V in industrial control modules.

IC Role / Device Role / Timing Role: Single-transistor snubberless switch using internal diode for energy recirculation during turn-off.

Use Value: Eliminates external RC snubber, saving 3–4 components and improving reliability in space-constrained enclosures.

Use Scenario: High-voltage startup transistor in auxiliary bias supply for SMPS controllers in 90–264 VAC adapters.

IC Role / Device Role / Timing Role: Provides initial gate drive to main MOSFET until V_CC rail is established; blocks 700 V during normal operation.

Use Value: Supports universal-input operation without transformer tap changes or additional HV capacitors, simplifying BOM for multi-output adapters.

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
BU2520DX	V_CES = 1000 V, I_C = 2 A, no integrated diode, TO-220FP package	Requires external fast diode; suited for higher-power (>60 W) ballasts with heatsink mounting	Select when higher voltage margin or thermal headroom is required; not drop-in due to package and diode absence
STN9360	V_CES = 600 V, I_C = 1.2 A, integrated diode, SOT-89 package, lower power dissipation (1.25 W)	Lower voltage rating limits use to 230 V-only systems; smaller footprint but reduced SOA	Choose for space-constrained 15–25 W designs where 600 V margin suffices and TO-92 mounting is impractical

Compared with BU2520DX and STN9360, STL73D uniquely balances 700 V capability, integrated diode, TO-92 mountability, and 1.5 W dissipation-making it optimal for cost-sensitive, medium-power CFL and auxiliary supply designs requiring minimal external components.

Availability

STL73D is available at Aetrix Electronics and suitable for compact fluorescent lamp ballasts, LED driver auxiliary supplies, snubberless inductive switching, and universal-input AC-DC adapter designs requiring stable component supply and long-term manufacturability.

Supply support for STL73D 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 applications.

The STL series was developed specifically for electronic ballast applications in energy-efficient lighting, emphasizing high-voltage ruggedness, fast switching, and integrated functionality to reduce system-level component count.

FAQ

What is the maximum safe operating frequency for STL73D in a CFL ballast?

The STL73D is characterized for reliable operation up to 70 kHz in resistive and inductive switching tests, with t_r/t_f ≤ 1 µs and t_s = 0.3 µs under inductive load. For sustained 20–40 W CFL operation, 40–60 kHz is recommended to maintain thermal margin below 150 °C junction temperature with standard PCB copper area.

Does STL73D require a base resistor in typical CFL driver circuits?

Yes - a base resistor is required to limit peak base current to ≤1.5 A and set appropriate I_B/I_C ratio. For 1 A collector current, the datasheet specifies I_B = 250 mA for full saturation; a 12–15 Ω resistor (1/4 W) is typical when driven from a 5 V logic source with transient protection.

Can STL73D replace a generic NPN transistor like BC547 in high-voltage applications?

No - BC547 has only 50 V V_CEO and 100 mA I_C, making it unsafe for mains-referenced circuits. STL73D's 700 V V_CES, 1.5 A rating, integrated diode, and optimized SOA are essential for fluorescent ballast operation; substitution would risk catastrophic failure.

Is the integrated diode in STL73D rated for continuous conduction?

The integrated diode is rated for 0.5 A forward current (V_F = 1.5 V) and is intended for short-duration freewheeling during transistor turn-off in switching applications. It is not designed for continuous DC conduction; sustained >100 mA average diode current requires thermal evaluation per R_thJC = 83 °C/W and PCB layout.

STL73D Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-226-3, TO-92-3 (TO-226AA)

Packaging:: Bag

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 1.5 A

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

Vce Saturation (Max) @ Ib, Ic:: 1V @ 250mA, 1A

Current - Collector Cutoff (Max):: -

DC Current Gain (hFE) (Min) @ Ic, Vce:: 10 @ 600mA, 3V

Power - Max:: 1.5 W

Frequency - Transition:: -

Operating Temperature:: -

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92-3

STL73D FAQ

1.How can I place an order for STL73D through Aetrix?

Please submit a Request for Quotation (RFQ) for STL73D 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 STL73D reliable?

The price and inventory of STL73D are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for STL73D is usually 5 days.

3.What payment methods are accepted for STL73D?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for STL73D transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for STL73D?

STL73D orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your STL73D 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 STL73D?

For technical support, including STL73D datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your STL73D requirements.

6.How does Aetrix verify that STL73D is sourced from the original manufacturer or authorized distributors?

All STL73D 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 STL73D meets industry standards.

7.What is the process for return or replacement of STL73D?

All STL73D units undergo pre-shipment inspection (PSI). If there is an issue with STL73D, 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 STL73D part is unused and in its original packaging.

Return procedure for STL73D:

1.Submit a request within 90 days.

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

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