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

Nexperia USA Inc. BST51,115

Name: BST51,115
Brand: Nexperia USA Inc.
SKU: BST51,115
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BST51,115

Manufacturer:: Nexperia USA Inc.

Category:: Single Bipolar Transistors

Package:: TO-243AA

Datasheet:: BST51,115.pdf

Description:: TRANS NPN DARL 60V 1A SOT-89

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BST51,115 from Nexperia is an AEC-Q101-qualified NPN Darlington transistor in SOT89 (SC-62) package, designed for industrial switching with 60 V V_CEO, 1 A continuous I_C, and minimum h_FE of 1000 at 150 mA. It integrates base-emitter clamping diode and resistor, enabling direct drive of solenoids, relays, and print hammers without external bias components.

For engineers reviewing the BST51,115 datasheet, BST51,115 pinout, BST51,115 application, or BST51,115 equivalent, key selection criteria include its Darlington gain structure, thermal resistance (R_th(j-sp) = 16 K/W), saturation voltage (V_CE(sat) ≤ 1.3 V @ 500 mA), and automotive-grade reliability under pulsed industrial loads.

Technical Context

The BST51,115 implements a monolithic NPN Darlington pair with integrated base-emitter clamp diode and series base resistor, reducing external component count in high-gain switching circuits. Its architecture delivers h_FE ≥ 2000 at 500 mA and supports fast switching with t_on ≤ 400 ns and t_off ≤ 1500 ns under defined test conditions.

Qualified to AEC-Q101, it operates across −65 °C to +150 °C ambient and junction temperature, with absolute maximum ratings including V_CBO = 80 V, V_EBO = 5 V, and P_tot = 1.3 W on FR4 PCB. Thermal design relies on low R_th(j-sp) = 16 K/W to solder point for efficient heat transfer in compact SMT layouts.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	60 V - Maximum collector-emitter voltage before breakdown; enables use in 48 V industrial bus and relay coil driving.
I_C (continuous)	1 A - Continuous collector current rating; supports sustained solenoid actuation without derating at T_amb ≤ 25 °C.
h_FE	1000–2000 - DC current gain range at 150–500 mA; ensures robust base drive margin and low control current requirements.
V_CE(sat)	≤1.3 V @ 500 mA/0.5 mA - Low saturation voltage minimizes power loss and self-heating during on-state operation.
R_th(j-sp)	16 K/W - Junction-to-solder-point thermal resistance; enables effective heat sinking through collector pad on standard FR4 PCB.
f_T	200 MHz - Transition frequency confirms usable bandwidth for pulse-width modulated (PWM) switching up to ~10–20 MHz.
t_off	≤1500 ns - Turn-off time under specified test conditions; defines maximum safe switching frequency in inductive load applications.

Pinout & Package

The BST51,115 is housed in a SOT89 (SC-62) surface-mount plastic package measuring 4.5 mm × 2.5 mm × 1.5 mm, with 1.5 mm lead pitch and exposed collector pad for thermal conduction.

Pin/Terminal	Circuit Role	Design Meaning
1 (E)	Emitter	Low-side return path; internally connected to emitter of second transistor in Darlington pair; requires low-impedance ground connection.
2 (C)	Collector	High-current output node; electrically and thermally tied to large copper pad on PCB for power dissipation and EMI reduction.
3 (B)	Base	Control input with integrated series resistor; accepts TTL/CMOS logic-level drive without external current-limiting resistor.

Key Features

Feature	Design Value
Integrated base resistor + clamp diode	Eliminates need for external bias network; reduces BOM count and layout area in relay/solenoid driver stages.
AEC-Q101 qualification	Validated for automotive-grade reliability including temperature cycling, HTRB, and ESD; suitable for harsh industrial environments.
SOT89 thermal performance	R_th(j-sp) = 16 K/W enables >800 mW power handling on standard FR4 without heatsink, supporting compact board designs.
Darlington h_FE ≥ 1000	Allows microcontroller GPIOs to directly switch 500 mA loads with <1 mA base drive, simplifying interface circuitry.

Applications

Print Hammer Driver

Solenoid Actuator

Use Scenario: Driving electromagnetic print hammers in dot-matrix printers requiring rapid on/off pulses with high peak current.

IC Role / Device Role / Timing Role: High-gain Darlington switch providing >500 mA pulsed collector current with sub-microsecond turn-on to meet dot timing resolution.

Use Value: Integrated base resistor enables direct MCU GPIO control; low V_CE(sat) reduces coil heating and extends hammer life.

Use Scenario: Controlling pneumatic/hydraulic solenoid valves in factory automation systems operating from 24 V DC rails.

IC Role / Device Role / Timing Role: Main power switch interfacing PLC outputs to inductive solenoid loads, absorbing flyback energy via internal clamp diode.

Use Value: AEC-Q101 qualification ensures long-term reliability under vibration and thermal cycling; R_th(j-sp) = 16 K/W maintains safe junction temperature during duty-cycled operation.

Relay Coil Driver

Lamp Load Switch

Use Scenario: Replacing mechanical relay contacts in programmable logic controllers for isolated control of AC/DC loads.

IC Role / Device Role / Timing Role: Solid-state replacement for electromechanical relays, delivering 1 A continuous current to relay coils with zero contact bounce.

Use Value: High h_FE allows single-stage drive from low-power controllers; integrated diode suppresses inductive kickback without external snubber.

Use Scenario: Switching incandescent or halogen indicator lamps in automotive dashboards and industrial HMIs.

IC Role / Device Role / Timing Role: Low-loss power switch managing inrush current and steady-state load, compatible with PWM dimming signals.

Use Value: V_CEO = 60 V accommodates 48 V vehicle systems; 1.3 V V_CE(sat) limits power dissipation to <650 mW at 500 mA, avoiding thermal shutdown.

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	SOT-323 package; lower I_C = 500 mA; no integrated base resistor; h_FE = 1000–3000.	Smaller footprint but higher thermal resistance (R_th(j-a) ≈ 270 K/W); requires external base resistor and flyback diode.	Select when board space is critical and thermal load is light; not drop-in due to missing integrated components.
Nexperia BST61,115	PNP complement; identical SOT89 package; symmetric V_CEO/I_C ratings but opposite polarity.	Used in high-side switching configurations where load connects to ground; shares same thermal and reliability specs.	Choose for complementary high-side drivers in H-bridge or dual-switch topologies; pinout is mirrored (E/C/B → E/C/B).

Compared with NSS12500UW3T1G, BST51,115 offers integrated protection and lower thermal resistance for higher power density; versus BST61,115, it provides NPN topology for low-side switching with identical qualification and package compatibility.

Availability

BST51,115 is available at Aetrix Electronics and suitable for industrial switching, automotive body electronics, and factory automation requiring stable component supply with AEC-Q101 assurance and SMT manufacturability.

Supply support for BST51,115 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 focused on high-volume, high-reliability discrete and logic devices, headquartered in Nijmegen, Netherlands, with manufacturing in Asia and Europe.

The BST51,115 belongs to Nexperia's AEC-Q101-qualified bipolar transistor portfolio, engineered specifically for robust industrial and automotive switching applications demanding high gain, integrated protection, and thermal efficiency in compact SMT packages.

FAQ

What is the maximum allowable base current for BST51,115?

The absolute maximum base current is 100 mA per the datasheet Limiting Values table. However, typical operation uses ≤0.5 mA base drive to achieve 500 mA collector current due to its Darlington h_FE ≥ 2000. Exceeding 100 mA risks permanent damage to the internal base resistor and transistor junctions.

Can BST51,115 replace a standard NPN transistor like BC817 in relay driver circuits?

Yes, but only if the BC817 circuit lacks external base resistors and flyback diodes. BST51,115 integrates both, so replacing BC817 requires removing those components. Its higher h_FE and V_CEO improve noise immunity and voltage margin, but its slower t_off (1500 ns vs. ~200 ns for BC817) may limit high-frequency PWM use.

Does BST51,115 require a heatsink in 1 A continuous operation?

No external heatsink is required at 1 A if mounted on an FR4 PCB with a 6 cm² collector pad, as its R_th(j-a) = 96 K/W yields ~92 °C junction rise above ambient at 25 °C. At 150 °C max T_j, this allows ~1.3 W dissipation-matching its P_tot rating-so thermal design must ensure adequate copper area and airflow.

Is the marking code 'AS2' unique to BST51,115?

Yes, 'AS2' is the official top-side marking for BST51,115 per Nexperia's ordering information table. It distinguishes this variant from other BST5x series parts (e.g., BST52 uses 'AS3') and confirms full AEC-Q101 qualification and SOT89 packaging-critical for traceability in automotive and industrial audits.

BST51,115 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):: 60 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

BST51,115 FAQ

1.How can I place an order for BST51,115 through Aetrix?

Please submit a Request for Quotation (RFQ) for BST51,115 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 BST51,115 reliable?

The price and inventory of BST51,115 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BST51,115 is usually 5 days.

3.What payment methods are accepted for BST51,115?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BST51,115 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BST51,115?

BST51,115 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BST51,115 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 BST51,115?

For technical support, including BST51,115 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BST51,115 requirements.

6.How does Aetrix verify that BST51,115 is sourced from the original manufacturer or authorized distributors?

All BST51,115 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 BST51,115 meets industry standards.

7.What is the process for return or replacement of BST51,115?

All BST51,115 units undergo pre-shipment inspection (PSI). If there is an issue with BST51,115, 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 BST51,115 part is unused and in its original packaging.

Return procedure for BST51,115:

1.Submit a request within 90 days.

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

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