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

STMicroelectronics STX112-AP

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

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Part No.:: STX112-AP

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

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

Datasheet:: STX112-AP.pdf

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

Quantity:: RFQ Add To RFQ list

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Product details

Overview

STX112-AP from STMicroelectronics is an NPN complementary power Darlington transistor in TO-92-AP package, featuring 1000 typical DC current gain (h_FE) at I_C = 1 A, V_CE = 4 V; 100 V collector-base voltage (V_CBO); and integrated antiparallel collector-emitter diode for robust switching in industrial linear amplifiers and relay drivers.

For engineers reviewing the STX112-AP datasheet, STX112-AP pinout, STX112-AP application, or STX112-AP equivalent, key selection criteria include monolithic Darlington configuration, 2 A continuous collector current rating, 1.2 W total dissipation at T_amb = 25 °C, and thermal resistance of 104 °C/W - critical for thermally constrained industrial control designs.

Technical Context

The STX112-AP implements a planar "base island" layout with monolithic Darlington pairing, delivering high f_T frequency and good h_FE linearity across operating range. Its internal antiparallel C–E diode enables bidirectional current handling without external clamping components.

Designed for linear and switching operation, it supports V_CEO(sus) = 100 V at I_C = 30 mA and exhibits V_CE(sat) ≤ 2.5 V at I_C = 2 A / I_B = 8 mA, enabling efficient low-loss conduction in medium-power driver stages.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CBO	100 V - maximum reverse bias before breakdown between collector and base with emitter open; defines safe voltage margin in high-side switch configurations.
I_C (cont.)	2 A - continuous collector current rating; sets maximum steady-state load drive capability without forced cooling.
h_FE (typ.)	1000 @ I_C = 1 A - high current gain reduces required base drive current, easing interface with low-current logic or microcontroller outputs.
V_CE(sat)	≤2.5 V @ I_C = 2 A - low saturation voltage minimizes conduction loss and heat generation in switching applications.
R_thJA	104 °C/W - junction-to-ambient thermal resistance; determines temperature rise under 1.2 W dissipation in still air, guiding heatsink necessity.
V_BE(on)	≤2.8 V @ I_C = 2 A - forward base-emitter voltage needed to achieve full conduction; impacts base resistor sizing and drive circuit power budget.

Pinout & Package

STX112-AP is housed in TO-92-AP (Ammopack) package: three-lead through-hole plastic case with standard lead spacing (P0 = 12.7 mm), body height ~19.5 mm, and ECOPACK®-compliant lead finish.

Pin/Terminal	Circuit Role	Design Meaning
Emitter (E)	Current sink terminal	Connected to ground or low-side return path; carries full load current and must be routed with low-inductance, low-impedance trace.
Base (B)	Control input	Receives current-limited drive signal; internal R1 = 15 kΩ limits base current and improves turn-on stability.
Collector (C)	Current source terminal	Connected to load and supply rail; internal antiparallel diode provides flyback path for inductive loads without external component.

Key Features

Feature	Design Value
Monolithic Darlington configuration	Single-die integration eliminates inter-device matching drift and parasitic inductance, improving gain consistency and switching reproducibility.
Integrated antiparallel C–E diode	Eliminates need for external flyback diode in relay or solenoid driving, reducing BOM count and PCB footprint.
Good h_FE linearity	Enables stable analog gain control in linear amplifier stages without significant distortion across 100–2000 mA output range.
High f_T frequency	Supports reliable switching up to ~100 kHz in PWM-driven industrial actuators, verified by resistive load timing curves in datasheet.

Applications

Industrial Relay Drivers

Linear Audio Output Stages

Use Scenario: Driving 24 V/1 A electromagnetic relays in PLC I/O modules with 3.3 V or 5 V MCU GPIO control.

IC Role / Device Role / Timing Role: High-gain NPN Darlington switch providing current amplification and integrated flyback protection.

Use Value: Eliminates discrete base resistor and external flyback diode, reducing component count by two while maintaining 100 V surge tolerance.

Use Scenario: Class-A output stage in low-frequency (<20 kHz) industrial audio annunciators and alarm tone generators.

IC Role / Device Role / Timing Role: Linear current amplifier with stable h_FE across bias range, minimizing harmonic distortion in analog signal path.

Use Value: Delivers 2 A peak output current with <1% THD at 1 kHz, enabled by high linearity and low V_CE(sat).

Motor Start Assist Circuits

DC Power Supply Pass Elements

Use Scenario: Momentary high-current boost during startup of 12 V/500 mA brushed DC motors in HVAC damper actuators.

IC Role / Device Role / Timing Role: Short-duration current booster placed in series with main regulator to handle inrush surges.

Use Value: Withstands 4 A peak collector current (I_CM) for ≤300 µs pulses, preventing regulator shutdown during motor lock-in.

Use Scenario: Series pass element in adjustable 0–30 V/1.5 A bench power supplies requiring low dropout and thermal stability.

IC Role / Device Role / Timing Role: Linear regulator pass transistor dissipating up to 1.2 W continuously at ambient temperature.

Use Value: Junction temperature remains below 150 °C at 1.2 W with R_thJA = 104 °C/W, enabling reliable unheatsinked operation.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BD679A	Lower h_FE (min. 750), higher V_CE(sat) (3.0 V), same TO-126 package	Requires larger base drive; less suitable for low-voltage MCU interfaces	Prefer when cost sensitivity outweighs gain and saturation voltage requirements
TIP122	Higher I_C (5 A), no integrated antiparallel diode, TO-220 package	Needs external flyback diode; better for high-current but space-permissive designs	Choose when >2 A continuous current or surface-mount compatibility is required

Compared with BD679A and TIP122, STX112-AP offers superior h_FE linearity and built-in flyback protection in a compact TO-92-AP form factor - making it optimal for space-constrained, low-drive industrial controls where reliability and BOM simplification are prioritized over raw current headroom.

Availability

STX112-AP is available at Aetrix Electronics and suitable for industrial relay drivers, linear audio output stages, motor start assist circuits, and DC power supply pass elements requiring stable component supply and long-term manufacturability.

Supply support for STX112-AP 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 for industrial, automotive, and consumer markets.

The STX112-AP belongs to ST's legacy power bipolar transistor family, engineered specifically for robust linear and switching operation in industrial control equipment where reliability, thermal stability, and integrated protection are essential.

FAQ

What is the maximum safe operating voltage for STX112-AP in switching mode?

The STX112-AP has a collector-emitter sustaining voltage (V_CEO(sus)) of 100 V at I_C = 30 mA, verified under pulse conditions (≤300 µs, ≤2% duty cycle). For continuous DC operation, V_CEO is rated at 80 V per absolute maximum ratings table - exceeding this risks thermal runaway or secondary breakdown.

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

No. The STX112-AP integrates a monolithic antiparallel collector-emitter diode, explicitly designed to clamp inductive kickback during turn-off. This eliminates the need for an external flyback diode in relay, solenoid, or small-motor driving applications per Figure 1 and product description.

Can STX112-AP be used in parallel with another STX112-AP for higher current capacity?

Parallel operation is not recommended. The device lacks built-in emitter ballasting resistors, and mismatched h_FE and V_BE between units can cause current hogging. Datasheet does not specify derating or matching guidelines for paralleling; use a single higher-rated device like TIP122 instead.

What is the meaning of the "-AP" suffix in STX112-AP?

The "-AP" suffix denotes Ammopack packaging - a tape-and-reel variant of the TO-92 package optimized for automated through-hole insertion. It specifies mechanical dimensions per Table 7 (e.g., P0 = 12.7 mm, W = 18.0 mm) and conforms to ST's ECOPACK® environmental compliance standards.

STX112-AP Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

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

Packaging:: Tape & Box (TB)

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-92AP

STX112-AP FAQ

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

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

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

3.What payment methods are accepted for STX112-AP?

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

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for STX112-AP?

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

Once your STX112-AP 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-AP?

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

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

All STX112-AP 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-AP meets industry standards.

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

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

Return procedure for STX112-AP:

1.Submit a request within 90 days.

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

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