Send an Inquiry

To receive a quote for your project, please fill in the following information, and we’ll get back to you promptly.

Submit Inventory List

Please fill in the following information, and we’ll get back to you promptly.

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

STMicroelectronics STL73

Name: STL73
Brand: STMicroelectronics
SKU: STL73
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: STL73

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

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

Datasheet:: STL73.pdf

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

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:4,910

Please send an inquiry. Send us your inquiry, and we will respond immediately.

Product details

Overview

STL73 from STMicroelectronics is a medium-voltage, fast-switching NPN power transistor in TO-92 package, rated for V_CEO = 400 V, I_C = 1.5 A, P_tot = 1.1 W at T_C = 25 °C, with t_f = 0.3 µs (inductive load), and designed specifically for compact fluorescent lamp (CFL) ballast circuits.

For engineers reviewing the STL73 datasheet, STL73 pinout, STL73 application, or STL73 equivalent, key selection criteria include its 400 V sustaining voltage under zero-base-drive conditions, low saturation voltage (V_CE(sat) ≤ 0.4 V at I_C = 0.6 A), group-specified h_FE (L/H), and validated switching performance in resonant CFL half-bridge topologies.

Technical Context

The STL73 employs high-voltage Multi-Epitaxial Planar technology with Cellular Emitter structure and planar edge termination to simultaneously achieve high switching speed and wide RBSOA. It supports pulsed operation up to 3 A (t_p < 5 ms) and operates reliably at T_J up to 150 °C.

Its switching behavior is characterized under both resistive (t_r/t_s/t_f = 1/4/0.7 µs) and inductive (t_f = 0.3 µs, V_Clamp = 300 V, L = 3 mH) loads, with pre-selected DC current gain groups (L: h_FE = 10–16, H: h_FE = 15–21 at I_C = 0.6 A).

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	400 V - Sustaining voltage with open base, enabling safe operation in CFL half-bridge flyback and resonant modes.
I_C	1.5 A continuous - Supports lamp power levels up to ~30 W in standard CFL electronic ballasts.
V_CE(sat)	0.4 V max at I_C = 0.6 A, I_B = 120 mA - Minimizes conduction loss and thermal stress during on-state.
t_f (inductive)	0.3 µs - Enables high-frequency switching (>50 kHz) with low turn-off energy loss in resonant CFL drivers.
h_FE Group	L (10–16) or H (15–21) - Pre-sorted gain bins ensure consistent base drive design across production lots.
R_thj-amb	112 °C/W - Defines thermal derating limit; requires heatsinking or airflow for sustained >0.5 W dissipation.

Pinout & Package

STL73 is housed in a TO-92 plastic package with standard lead configuration: Emitter (pin 1), Base (pin 2), Collector (pin 3), as confirmed by STMicroelectronics mechanical drawing 0102782 C and internal schematic (Figure 2).

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (Emitter)	Current exit path from transistor	Connected to ground or low-side return in CFL half-bridge; referenced for base drive biasing.
Pin 2 (Base)	Control terminal for minority-carrier injection	Driven by dedicated oscillator/driver IC (e.g., IRS2153D); requires precise current limiting due to h_FE binning.
Pin 3 (Collector)	High-voltage current input node	Switches 400 V rail in series with resonant tank; must withstand V_CE spikes up to 700 V transiently.

Key Features

Feature	Design Value
Cellular Emitter Structure	Enables simultaneous high-speed switching (t_f = 0.3 µs) and robust RBSOA for lamp ignition surges.
Planar Edge Termination	Prevents premature edge breakdown at 400 V, improving long-term reliability in thermally cycled CFL fixtures.
Pre-Selected h_FE Groups	Reduces base drive component variation across manufacturing lots-critical for consistent lamp start-up timing.
Multi-Epitaxial Planar Process	Delivers stable dynamic parameters (t_r, t_s, t_f) with minimal lot-to-lot spread (<±15%).

Applications

Compact Fluorescent Lamp (CFL) Ballasts

Electronic Starter Circuits

Use Scenario: High-frequency (30–70 kHz) half-bridge resonant inverter driving 11–23 W spiral CFL tubes.

IC Role / Device Role / Timing Role: Main switching element in low-side position; commutates resonant current with controlled fall time.

Use Value: 0.3 µs inductive fall time minimizes switching loss during lamp ignition, extending electrolytic capacitor life.

Use Scenario: Preheat and ignition phase control in integrated CFL modules with single-transistor topology.

IC Role / Device Role / Timing Role: Fast-turn-off switch enabling precise preheat duration (typically 0.5–2 s) before high-voltage strike.

Use Value: Tight V_CEO(sus) = 400 V tolerance ensures reliable hold-off during filament preheat without snubber overhead.

DC-AC Inverters for LED Drivers

Low-Power Induction Heating Stages

Use Scenario: Auxiliary 12–24 V AC output stage in hybrid LED+CFL retrofit lamps.

IC Role / Device Role / Timing Role: Medium-voltage switch interfacing between DC bus and transformer-coupled AC output winding.

Use Value: 700 V V_CES rating provides margin against reflected transients from transformer leakage inductance.

Use Scenario: 10–20 W resonant tank driver in portable induction cooktop demo units.

IC Role / Device Role / Timing Role: Low-loss switching device in Class-E or LLC sub-circuit operating at 100–300 kHz.

Use Value: Low V_CE(sat) (≤0.4 V) and fast t_f reduce conduction + switching losses, enabling passive cooling.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BU2508AX	V_CEO = 800 V, I_C = 8 A, TO-126 package, higher P_tot (12.5 W)	Designed for TV horizontal deflection; over-specified voltage/current for CFL use	Requires PCB layout redesign and larger heatsink; not cost-optimized for <30 W ballasts.
BD139	V_CEO = 80 V, I_C = 1.5 A, TO-126, h_FE = 25–250 (unbinned)	Not rated for CFL line-referenced switching; fails at V_CE > 120 V	Unsuitable for direct replacement-lacks 400 V sustaining capability and controlled dynamic parameters.

Compared with BU2508AX and BD139, the STL73 uniquely balances 400 V capability, 0.3 µs inductive fall time, and TO-92 form factor for space-constrained CFL ballasts-neither over-engineered nor electrically marginal.

Availability

STL73 is available at Aetrix Electronics and suitable for compact fluorescent lamp ballasts, electronic starter modules, low-power DC-AC inverters, and resonant induction heating stages requiring stable component supply and consistent h_FE binning.

Supply support for STL73 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, specializing in power discrete devices, microcontrollers, and analog ICs for industrial, automotive, and consumer applications.

The STL series was developed specifically for high-reliability, medium-voltage switching in compact fluorescent lighting systems-emphasizing parameter consistency, thermal robustness, and fast turn-off in resonant topologies.

FAQ

What is the maximum allowable collector-emitter voltage during transient conditions?

The STL73 is rated for V_CES = 700 V with base open, verified per absolute maximum ratings table. This rating applies to non-repetitive surge conditions such as lamp ignition spikes in CFL ballasts, provided pulse duration remains ≤300 µs and duty cycle ≤1.5%.

Does STL73 require external base current limiting in CFL driver circuits?

Yes-due to h_FE binning (Group L/H), base drive must be designed with current-limiting resistors or active control to ensure consistent switching behavior across production lots and prevent thermal runaway at elevated junction temperatures.

Can STL73 be used in surface-mount designs?

No-STL73 is exclusively offered in through-hole TO-92 package (mechanical drawing 0102782 C). No SMD variant (e.g., SOT-23, SOT-89) exists in the STL family; alternative packages would require redesign of thermal and mechanical interfaces.

How does the Cellular Emitter structure improve reliability in CFL applications?

The Cellular Emitter design enhances current spreading uniformity during high di/dt events (e.g., lamp strike), reducing localized hot-spot formation and delaying second-breakdown onset-extending operational lifetime in thermally cycling CFL fixtures beyond 10,000 hours.

STL73 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:: 1.1 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92-3

STL73 FAQ

1.How can I place an order for STL73 through Aetrix?

Please submit a Request for Quotation (RFQ) for STL73 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 STL73 reliable?

The price and inventory of STL73 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for STL73 is usually 5 days.

3.What payment methods are accepted for STL73?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for STL73 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for STL73?

STL73 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your STL73 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 STL73?

For technical support, including STL73 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your STL73 requirements.

6.How does Aetrix verify that STL73 is sourced from the original manufacturer or authorized distributors?

All STL73 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 STL73 meets industry standards.

7.What is the process for return or replacement of STL73?

All STL73 units undergo pre-shipment inspection (PSI). If there is an issue with STL73, 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 STL73 part is unused and in its original packaging.

Return procedure for STL73:

1.Submit a request within 90 days.

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

Tech Hub

2026-09-08 Obsolete Electronic Components: How to Source and Evaluate Replacements

A practical engineering and sourcing framework covering lifecycle verification, lifetime-buy calculations, replacement qualification, supplier checks and counterfeit-risk controls.

2026-09-07 TTL vs CMOS Logic Levels: 74HC and 74HCT Compatibility Explained

TTL and CMOS logic families differ in thresholds, loading, output drive, power and timing. This engineering guide compares 74HC and 74HCT, calculates noise margins and checks 3.3 V/5 V compatibility.

2026-09-04 Logic Level Shifter: How to Connect 3.3V and 5V Logic Safely

A practical engineering guide to 3.3V and 5V logic compatibility, input thresholds, resistor dividers, translator ICs, MOSFET level shifting, I2C pull-ups, timing limits and power-sequencing risks.

2026-09-03 74HC595 vs TPIC6B595: Output Drive, Pinout, Current, and Load Selection

The 74HC595 uses push-pull logic outputs, while the TPIC6B595 uses 50 V open-drain DMOS sinks for higher-power loads. This guide compares timing, current limits, 3.3 V interfacing, load wiring, thermal…

2026-09-02 74HC595 Pinout, Timing, Output Current, and Applications

The 74HC595 converts serial data into eight stable parallel outputs. This guide covers pin functions, shift and storage timing, OE and MR behavior, drive-current limits, cascading, voltage compatibilit…

2026-09-01 Latch vs Flip-Flop: Timing, Differences and Design Choices

A technical comparison of level-sensitive latches and edge-triggered flip-flops, covering timing windows, setup and hold limits, master–slave operation, time borrowing, race-through, HDL inference and…

2026-08-30 D Latch Circuit: Truth Table, Timing, ICs and Applications

A D latch stores one bit while Enable controls when data can pass. This reference covers gate-level operation, truth tables, transparency, setup and hold timing, LE versus OE, common ICs and practical …

2026-08-28 SR Latch Explained: NOR and NAND Circuits, Truth Tables, and Applications

An SR latch stores one bit through cross-coupled feedback. This engineering reference covers NOR and NAND implementations, truth tables, forbidden-state recovery, gated operation, switch debouncing, fa…

2026-08-27 Latch Circuit: SR and D Latches, Truth Tables, Timing, and Applications

Latch circuits retain one bit through feedback. This technical reference covers SR and D latches, truth tables, transparency, timing limits, latch-versus-flip-flop behavior, applications and common log…

2026-08-21 What Is an LED Driver? Types, Circuits, Dimming, and Selection

An engineering guide to LED driver operation, constant-current and constant-voltage outputs, linear and switching topologies, dimming, IC selection, calculations, replacement compatibility, and fault c…