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

STMicroelectronics STX112

Name: STX112
Brand: STMicroelectronics
SKU: STX112
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: STX112

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

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

Datasheet:: STX112.pdf

Description:: TRANS NPN DARL 100V 2A TO-92-3

Quantity:: RFQ Add To RFQ list

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Inventory:4,185

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Product details

Overview

STX112 from STMicroelectronics is an NPN complementary power Darlington transistor in TO-92-AP package, featuring monolithic Darlington configuration with integrated antiparallel collector-emitter diode, hFE ≥ 500 at IC = 2 A, VCEO = 100 V, and VCE(sat) ≤ 2.5 V at IC = 2 A / IB = 8 mA. It is used in industrial linear amplification and switching circuits requiring high current gain and robust voltage handling.

For engineers reviewing the STX112 datasheet, STX112 pinout, STX112 application, or STX112 equivalent, key selection criteria include DC current gain linearity at high collector current, collector-emitter sustaining voltage under switching conditions, thermal resistance (RthJA = 104 °C/W), and integrated antiparallel diode functionality for inductive load commutation.

Technical Context

The STX112 implements a monolithic Darlington pair with base island planar technology, delivering high fT frequency and good hFE linearity across IC = 1–2 A. Its internal antiparallel collector-emitter diode enables bidirectional current handling without external flyback components.

It operates with VBE(on) ≤ 2.8 V at IC = 2 A and VCE = 4 V, and exhibits ICEO ≤ 2 mA at VCE = 50 V, supporting stable biasing in linear-mode industrial amplifiers and fast-switching control stages in relay drivers and motor interface circuits.

Key Specifications

Parameter	Value and Actual Design Meaning
Collector-emitter voltage	VCEO = 100 V - supports operation in 48 V industrial bus systems with margin against transients
DC current gain	hFE ≥ 500 @ IC = 2 A - enables low-base-drive-current switching of 2 A loads with minimal driver overhead
Collector saturation voltage	VCE(sat) ≤ 2.5 V @ IC = 2 A / IB = 8 mA - limits conduction loss to ≤ 5 W at full load
Thermal resistance	RthJA = 104 °C/W - requires heatsinking above ~0.6 W dissipation for safe 150 °C junction operation
Integrated diode	Antiparallel C–E diode - eliminates need for external freewheeling diode in inductive load switching
Base-emitter on voltage	VBE(on) ≤ 2.8 V @ IC = 2 A - ensures reliable turn-on with standard 3.3 V or 5 V logic-level drivers

Pinout & Package

STX112 is housed in TO-92-AP (Ammopack) plastic package with standard three-terminal lead configuration: Emitter (pin 1), Base (pin 2), Collector (pin 3), as confirmed by STMicroelectronics mechanical drawing Doc ID 6881 Rev 4, page 7.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (Emitter)	Current sink terminal	Connected to ground or low-side return path; carries full load current with minimal voltage drop
Pin 2 (Base)	Control input	Receives low-current drive (≤8 mA) to saturate Darlington; internal R1 = 15 kΩ resistor to base
Pin 3 (Collector)	High-side output	Connects to load supply rail; integrates antiparallel diode for inductive energy recirculation

Key Features

Feature	Design Value
Monolithic Darlington + diode	Single-die integration eliminates discrete diode placement error and parasitic inductance in flyback paths
hFE linearity	Gain remains ≥500 from IC = 1 A to 2 A - ensures predictable base drive scaling across operating range
High fT frequency	Enables usable bandwidth >1 MHz in small-signal amplifier configurations despite power device classification
ECOPACK® compliance	Meets RoHS and halogen-free requirements per ST's environmental grade definitions (Doc ID 6881 Rev 4, p.6)

Applications

Industrial Relay Driver

Linear Audio Amplifier Stage

Use Scenario: Driving 24 V/1 A electromagnetic relays in PLC I/O modules with inductive kickback suppression.

IC Role / Device Role / Timing Role: High-gain NPN Darlington switch providing low-loss, self-commutated load control.

Use Value: Integrated antiparallel diode eliminates external snubber, reducing BOM count and PCB area by one component.

Use Scenario: Output stage in Class-AB audio amplifiers for public address systems requiring <1% THD at 1 W.

IC Role / Device Role / Timing Role: Linear-mode current booster delivering 2 A peak into 4 Ω speaker load.

Use Value: hFE linearity ensures consistent bias stability and low crossover distortion across temperature and signal swing.

DC Motor Direction Control

Power Supply Pass Transistor

Use Scenario: Low-side switch in H-bridge half-bridge section controlling 12 V brushed DC motors up to 1.5 A.

IC Role / Device Role / Timing Role: Complementary NPN switch paired with STX117 PNP for bidirectional drive.

Use Value: VCEO = 100 V provides 8× margin over 12 V rail, enabling robust operation during back-EMF spikes.

Use Scenario: Series pass element in adjustable linear regulators supplying 5 V/1.8 A to FPGA core rails.

IC Role / Device Role / Timing Role: Voltage-controlled current source regulating output via feedback loop.

Use Value: VCE(sat) ≤ 2.5 V at 2 A limits dropout voltage and thermal stress under full load.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN Darlington transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
TIP122	VCEO = 100 V, hFE = 1000 min @ IC = 1 A, no integrated antiparallel diode	Requires external flyback diode for inductive loads; higher gain at lower current	Preferred where maximum hFE at light load is critical and board space allows discrete diode
BD679	VCEO = 80 V, hFE = 750 min @ IC = 1 A, includes integrated diode but TO-126 package	Lower voltage rating limits use to ≤24 V systems; larger footprint than TO-92	Selected when integrated diode is required and thermal mass of TO-126 improves power dissipation

Compared with TIP122 and BD679, STX112 uniquely combines TO-92 form factor, 100 V rating, integrated antiparallel diode, and verified hFE ≥ 500 at 2 A - making it optimal for space-constrained industrial switching where both voltage margin and diode integration are mandatory.

Availability

STX112 is available at Aetrix Electronics and suitable for industrial relay drivers, linear audio amplifier stages, DC motor direction control circuits, and linear regulator pass transistor applications requiring stable component supply and long-term manufacturability.

Supply support for STX112 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, power, microcontroller, and sensor solutions for industrial, automotive, and consumer markets.

STX112 belongs to ST's legacy power bipolar transistor product line, engineered specifically for industrial linear and switching applications demanding high current gain, rugged voltage capability, and integrated protection features in compact through-hole packages.

FAQ

What is the maximum continuous collector current for STX112?

The absolute maximum rated continuous collector current (IC) is 2 A at Tamb = 25 °C. Derating is required above 25 °C ambient per the RthJA = 104 °C/W thermal resistance; at 70 °C ambient, max IC drops to approximately 1.15 A to maintain TJ ≤ 150 °C.

Does STX112 require an external flyback diode when driving inductive loads?

No. STX112 integrates a monolithic antiparallel collector-emitter diode, explicitly designed to handle inductive kickback without external components. This is confirmed in the device description and internal schematic (Figure 1, Doc ID 6881 Rev 4).

How does STX112 differ from STX117?

STX112 is NPN; STX117 is its complementary PNP counterpart. Both share identical TO-92-AP packaging, 100 V VCEO rating, and monolithic Darlington + diode architecture, enabling matched pair usage in push-pull or H-bridge topologies with consistent thermal and gain characteristics.

Is STX112 suitable for automotive applications?

STX112 is not qualified as automotive-grade per ST's documentation. It lacks AEC-Q101 qualification and is specified only for industrial equipment per the "Application" section of Doc ID 6881 Rev 4. Use in automotive contexts is at the designer's own risk and requires full system-level validation.

STX112 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

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

Packaging:: Bulk

Product Status:: Obsolete

Transistor Type:: NPN - Darlington

Current - Collector (Ic) (Max):: 2 A

Voltage - Collector Emitter Breakdown (Max):: 100 V

Vce Saturation (Max) @ Ib, Ic:: 2.5V @ 8mA, 2A

Current - Collector Cutoff (Max):: 2mA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 1000 @ 1A, 4V

Power - Max:: 1.2 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-92-3

STX112 FAQ

1.How can I place an order for STX112 through Aetrix?

Please submit a Request for Quotation (RFQ) for STX112 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 STX112 reliable?

The price and inventory of STX112 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for STX112 is usually 5 days.

3.What payment methods are accepted for STX112?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for STX112 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for STX112?

STX112 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your STX112 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 STX112?

For technical support, including STX112 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your STX112 requirements.

6.How does Aetrix verify that STX112 is sourced from the original manufacturer or authorized distributors?

All STX112 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 STX112 meets industry standards.

7.What is the process for return or replacement of STX112?

All STX112 units undergo pre-shipment inspection (PSI). If there is an issue with STX112, 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 STX112 part is unused and in its original packaging.

Return procedure for STX112:

1.Submit a request within 90 days.

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

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