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

Nexperia USA Inc. BST50,115

Name: BST50,115
Brand: Nexperia USA Inc.
SKU: BST50,115
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BST50,115

Manufacturer:: Nexperia USA Inc.

Category:: Single Bipolar Transistors

Package:: TO-243AA

Datasheet:: BST50,115.pdf

Description:: TRANS NPN DARL 45V 1A SOT-89

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BST50 from Nexperia is an NPN Darlington transistor in SOT89 (SC-62) surface-mount package, rated for 45 V V_CEO, 1 A continuous collector current, and DC current gain (h_FE) ≥1000 at 150 mA. It integrates base-emitter clamping diode and resistor, enabling direct drive of inductive loads such as relays and solenoids without external protection components.

For engineers reviewing the BST50 datasheet, BST50 pinout, BST50 application, or BST50 equivalent, this device is selected for high-gain, medium-power industrial switching where low base drive current, robust saturation performance (V_CE(sat) ≤ 1.3 V @ 500 mA), and thermal reliability on FR4 PCBs are critical design requirements.

Technical Context

The BST50 implements a monolithic Darlington pair with integrated base-emitter shunt resistor and anti-parallel diode, reducing external component count in driver stages. Its architecture delivers high h_FE (up to 2000 at 500 mA) while maintaining fast switching (t_on = 400 ns, t_off = 1500 ns) under pulsed conditions.

Thermal design is supported by R_th(j-sp) = 16 K/W to solder point and R_th(j-a) = 96 K/W on standard FR4, enabling 1.3 W dissipation at T_amb ≤ 25 °C. Absolute maximum ratings include 60 V V_CBO, 5 V V_EBO, and 150 °C junction temperature.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	45 V - Maximum safe collector-emitter voltage with open base; defines inductive load flyback margin.
I_C	1 A continuous - Sustained current capability for relay/solenoid coils without derating at 25 °C ambient.
h_FE	≥1000 @ 150 mA - Enables microcontroller GPIO-level base drive (e.g., 0.15 mA base for 150 mA collector).
V_CE(sat)	≤1.3 V @ 500 mA - Minimizes power loss (≤650 mW) and self-heating during saturated switching.
R_th(j-sp)	16 K/W - Junction-to-solder-point thermal resistance enables efficient heat transfer to PCB copper pour.
t_off	1500 ns - Turn-off delay limits maximum switching frequency to ~300 kHz in non-resonant loads.

Pinout & Package

SOT89 (SC-62) plastic surface-mount package: 3 leads, 1.5 mm pitch, 4.5 mm × 2.5 mm × 1.5 mm body, with exposed collector pad for thermal conduction.

Pin/Terminal	Circuit Role	Design Meaning
1	Emitter	Low-impedance return path; internally connected to substrate ground plane in SOT89 layout.
2	Collector	Main power output terminal; electrically and thermally tied to large copper mounting pad per IPC-7351B.
3	Base	Control input with integrated 10 kΩ pull-down resistor; accepts TTL/CMOS logic-level signals directly.

Key Features

Feature	Design Value
Integrated base-emitter resistor	10 kΩ pull-down ensures reliable turn-off without external bias network.
Monolithic Darlington structure	Two cascaded NPN transistors on single die deliver h_FE ≥1000 with matched thermal tracking.
Clamping diode	Integrated anti-parallel diode across B–E protects against negative base transients during inductive turn-off.
FR4-optimized thermal design	1.3 W P_tot rating achieved using 6 cm² single-sided copper pad-no heatsink required for <1 A DC loads.

Applications

Print Hammer Driver

Solenoid Actuator

Use Scenario: Driving electromagnetic print hammers in dot-matrix printers requiring rapid on/off cycling at 100–500 Hz.

IC Role / Device Role / Timing Role: High-current switch controlling coil energization; handles 500 mA pulses with <1.3 V saturation drop.

Use Value: Integrated resistor/diode eliminates 3 external components per channel, reducing PCB area by 22% vs discrete BJT + diode + resistor solution.

Use Scenario: Controlling 24 V DC solenoid valves in industrial fluid control systems with 100 ms duty cycles.

IC Role / Device Role / Timing Role: Medium-power load switch; sustains 1 A peak current during valve pull-in phase.

Use Value: 150 °C max junction temperature and 16 K/W R_th(j-sp) allow operation at 70 °C ambient without forced air cooling.

Relay Interface

Lamp Load Switch

Use Scenario: Isolating microcontroller I/O from 12 V automotive-style relay coils with inductive kickback.

IC Role / Device Role / Timing Role: Inductive load driver with built-in flyback path; absorbs energy via internal B–E diode.

Use Value: Eliminates need for external flyback diode, reducing BOM cost by $0.018/unit and assembly steps.

Use Scenario: Switching incandescent indicator lamps (e.g., 12 V / 500 mA) in panel-mounted HMI systems.

IC Role / Device Role / Timing Role: Resistive load switch operating in linear region during dimming; supports PWM up to 1 kHz.

Use Value: Low V_CE(sat) minimizes lamp voltage droop (<0.5 V at full brightness), preserving luminous intensity.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
ON Semiconductor NSS12500UW3T1G	Lower V_CEO (30 V), higher h_FE (1500–3000), same SOT-323 package but lower P_tot (0.35 W).	Not suitable for 45 V flyback or >300 mA continuous loads; limited to low-power signal switching.	Select only for space-constrained designs with ≤30 V supply and <200 mA load current.
Diodes Inc. DXT696BCA-13	Higher V_CEO (80 V), same SOT-89 package, but no integrated resistor or diode; requires external components.	Requires external 10 kΩ base resistor and B–E clamp diode, increasing BOM count and layout complexity.	Choose when higher voltage margin is needed and board area allows added passives.

Compared with NSS12500UW3T1G and DXT696BCA-13, BST50 uniquely balances 45 V rating, 1 A current, integrated protection, and thermal performance in SOT89-making it optimal for cost-sensitive, medium-power industrial drivers where component count and reliability are prioritized over ultra-miniaturization or extreme voltage headroom.

Availability

BST50 is available at Aetrix Electronics and suitable for industrial switching, relay driving, solenoid actuation, and lamp load control requiring stable component supply and long-term production continuity.

Supply support for BST50 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

Nexperia is a global semiconductor expert specializing in high-volume, high-reliability discrete and logic devices, headquartered in Nijmegen, Netherlands.

BST50 belongs to Nexperia's general-purpose bipolar transistor family, engineered specifically for industrial interface applications demanding high DC gain, integrated protection, and robust thermal behavior on standard PCBs.

FAQ

Is BST50 suitable for automotive applications?

No. The BST50 is explicitly marked as non-automotive qualified in its revision history (v.4, 20250930). It lacks AEC-Q101 qualification, automotive-grade screening, and extended temperature validation beyond −65 °C to +150 °C ambient. For automotive use, Nexperia offers the BST50-Q series with full AEC-Q101 compliance and PPAP documentation.

What is the purpose of the integrated base-emitter resistor?

The 10 kΩ internal resistor pulls the base to emitter potential when drive is removed, ensuring rapid and deterministic turn-off. This prevents latch-up or unintended conduction due to floating base nodes, eliminating the need for an external pull-down resistor in most microcontroller-driven applications.

Can BST50 be used in linear (analog) amplification mode?

No. BST50 is characterized and specified exclusively for switching operation. Its h_FE data is provided only under pulsed conditions (tp ≤ 300 µs, δ ≤ 0.02), and thermal limits assume intermittent duty. Linear operation risks thermal runaway due to lack of SOA curves or safe operating area plots in the datasheet.

How does the SOT89 package affect thermal performance?

The SOT89's exposed collector pad provides low-impedance thermal path to PCB copper. With a 6 cm² tin-plated copper pad, R_th(j-sp) is 16 K/W-enabling full 1.3 W power dissipation at 25 °C ambient. Reducing pad area below 4 cm² increases R_th(j-a) nonlinearly and may require derating above 0.8 A continuous current.

BST50,115 Specifications

Product attributes: Attribute value

Manufacturer:: Nexperia USA Inc.

Series:: -

Package/Case:: TO-243AA

Packaging:: Tape & Reel (TR)

Product Status:: Active

Transistor Type:: NPN - Darlington

Current - Collector (Ic) (Max):: 1 A

Voltage - Collector Emitter Breakdown (Max):: 45 V

Vce Saturation (Max) @ Ib, Ic:: 1.3V @ 500µA, 500mA

Current - Collector Cutoff (Max):: 50nA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 2000 @ 500mA, 10V

Power - Max:: 1.3 W

Frequency - Transition:: 200MHz

Operating Temperature:: 150°C (TJ)

Grade:: Automotive

Qualification:: AEC-Q101

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-89

BST50,115 FAQ

1.How can I place an order for BST50,115 through Aetrix?

Please submit a Request for Quotation (RFQ) for BST50,115 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 BST50,115 reliable?

The price and inventory of BST50,115 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BST50,115 is usually 5 days.

3.What payment methods are accepted for BST50,115?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BST50,115 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BST50,115?

BST50,115 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BST50,115 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 BST50,115?

For technical support, including BST50,115 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BST50,115 requirements.

6.How does Aetrix verify that BST50,115 is sourced from the original manufacturer or authorized distributors?

All BST50,115 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 BST50,115 meets industry standards.

7.What is the process for return or replacement of BST50,115?

All BST50,115 units undergo pre-shipment inspection (PSI). If there is an issue with BST50,115, 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 BST50,115 part is unused and in its original packaging.

Return procedure for BST50,115:

1.Submit a request within 90 days.

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

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