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

Nexperia USA Inc. BST39-QX

Name: BST39-QX
Brand: Nexperia USA Inc.
SKU: BST39-QX
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

Compare

Part No.:: BST39-QX

Manufacturer:: Nexperia USA Inc.

Category:: Single Bipolar Transistors

Package:: TO-243AA

Datasheet:: BST39-QX.pdf

Description:: TRANS NPN 350V 0.1A SOT-89

Quantity:: RFQ Add To RFQ list

Payment:

Shipping:

Inventory:1,000

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

Product details

Overview

BST39-QX from Nexperia is an NPN high-voltage bipolar junction transistor in SOT89 (SC-62) package, rated for 350 V V_CEO, 100 mA I_C, and 70 MHz f_T, with AEC-Q101 qualification for automotive switching applications such as ignition coil drivers and LED ballasts.

For engineers reviewing the BST39-QX datasheet, BST39-QX pinout, BST39-QX application, or BST39-QX equivalent, key selection criteria include collector-emitter breakdown voltage, DC current gain at 20 mA, thermal resistance to solder point, saturation voltage under 50 mA/4 mA drive, and SOT89 PCB mounting requirements.

Technical Context

This device operates as a medium-speed, high-voltage NPN switch with fixed emitter-base and collector-base breakdown limits (V_EBO = 5 V, V_CBO = 400 V), enabling robust operation in flyback and inductive load circuits where voltage transients exceed 300 V.

Its 70 MHz transition frequency and 40 minimum h_FE at 20 mA support stable linear amplification and fast turn-off in pulse-width modulated power stages, while its 16 K/W R_th(j-sp) ensures reliable thermal coupling to PCB copper when mounted per SOT89 footprint guidelines.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	350 V - Maximum safe collector-emitter voltage with base open; defines upper limit for inductive kick tolerance in automotive relay or solenoid drivers.
I_C	100 mA - Continuous DC collector current rating; sets maximum steady-state load capability in low-power HV switching.
h_FE	40 min @ V_CE=10 V, I_C=20 mA - Minimum DC current gain; determines required base drive for full saturation in logic-level control interfaces.
V_CE(sat)	500 mV max @ I_C=50 mA, I_B=4 mA - Saturation voltage at rated switching current; directly impacts conduction loss and thermal rise in pulsed operation.
f_T	70 MHz - Transition frequency; supports reliable switching up to ~10 MHz with adequate gain margin in amplifier or oscillator configurations.
R_th(j-sp)	16 K/W - Junction-to-solder-point thermal resistance on FR4 PCB; enables accurate junction temperature estimation using pad temperature measurement.

Pinout & Package

The BST39-QX is housed in a SOT89 (SC-62) plastic surface-mount package measuring 4.5 mm × 2.5 mm × 1.5 mm, with 1.5 mm lead pitch and integrated heat-dissipating collector tab.

Pin/Terminal	Circuit Role	Design Meaning
1 (E)	Emitter	Reference terminal for biasing; connected to ground or low-side return path in common-emitter configurations.
2 (C)	Collector	Main high-voltage output node; electrically and thermally coupled to large PCB copper area via exposed tab for power dissipation.
3 (B)	Base	Control input requiring current-limited drive; 4 mA base current ensures full saturation at 50 mA collector load.

Key Features

Feature	Design Value
AEC-Q101 qualified	Validated for automotive-grade reliability including temperature cycling, HTRB, and ESD testing-enables use in under-hood modules without additional qualification.
High V_CBO = 400 V	Provides 50 V margin above V_CEO rating, improving immunity to voltage spikes in inductive switching circuits like fuel injectors.
Low I_CBO = 20 nA max	Minimizes leakage-induced offset drift in high-impedance bias networks and improves stability in precision timing or sensing front-ends.
SOT89 thermal performance	16 K/W R_th(j-sp) allows >1 W power handling with proper PCB layout-eliminates need for external heatsinks in space-constrained designs.

Applications

Automotive Ignition Coils

LED Constant-Current Ballasts

Use Scenario: Switching 300–350 V flyback pulses in distributorless ignition systems.

IC Role / Device Role / Timing Role: High-voltage NPN switch controlling primary coil current; turns off rapidly to induce secondary spark voltage.

Use Value: 350 V V_CEO withstands back-EMF; 70 MHz f_T ensures clean turn-off edge; AEC-Q101 ensures lifetime reliability at 125 °C ambient.

Use Scenario: Regulating current through high-brightness LED strings in headlamps or DRLs.

IC Role / Device Role / Timing Role: Linear pass element in constant-current source topology, dissipating excess voltage across collector-emitter.

Use Value: 100 mA I_C matches typical LED string current; 500 mV V_CE(sat) minimizes power loss; SOT89 tab enables direct thermal coupling to metal-core PCB.

Industrial Relay Drivers

AC Mains-Sensing Circuits

Use Scenario: Driving 24 V or 48 V DC coils in programmable logic controller (PLC) output modules.

IC Role / Device Role / Timing Role: Low-side switch interfacing microcontroller GPIO to inductive relay load.

Use Value: 40 h_FE ensures sufficient gain for 3.3 V logic drive; 350 V rating prevents failure during coil de-energization transients.

Use Scenario: Zero-crossing detection and voltage monitoring in smart AC adapters or energy meters.

IC Role / Device Role / Timing Role: High-impedance voltage divider buffer stage isolating mains-referenced signals from low-voltage MCU inputs.

Use Value: 20 nA I_CBO prevents false triggering; 5 V V_EBO permits safe biasing from optocoupler outputs; SOT89 footprint simplifies creepage/clearance layout.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN high-voltage switching applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BCV61B,215	Lower V_CEO (160 V), higher h_FE (100–630), same SOT89 package	Not suitable for >200 V applications; better for general-purpose amplification at lower voltages	Select only if operating voltage stays below 160 V and higher gain is prioritized over HV robustness.
BUV27,127	Higher V_CEO (1000 V), TO-126 package, 500 mA I_C	Requires through-hole mounting and larger board area; suited for higher-power industrial SMPS	Choose when >350 V standoff or >100 mA continuous current is required, accepting larger footprint and assembly cost.

Compared with BCV61B and BUV27, the BST39-QX uniquely balances 350 V capability, AEC-Q101 compliance, and SOT89 thermal efficiency-making it optimal for space-constrained automotive and industrial HV switching where reliability and board area are critical.

Availability

BST39-QX is available at Aetrix Electronics and suitable for automotive ignition systems, LED lighting ballasts, industrial relay drivers, and AC mains-sensing circuits requiring stable component supply and long-term lifecycle assurance.

Supply support for BST39-QX 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, with leadership in automotive-qualified components and advanced packaging technologies.

The BST39-QX belongs to Nexperia's high-voltage bipolar transistor product line, engineered specifically for automotive and industrial switching applications demanding robust transient immunity, precise gain control, and thermally efficient SMT integration.

FAQ

What is the maximum allowable junction temperature for BST39-QX?

The BST39-QX has a maximum junction temperature (T_j) of 150 °C, as defined in its Absolute Maximum Ratings. This limit applies under all operating conditions, including transient loads. Thermal design must ensure T_j remains ≤150 °C using the specified R_th(j-a) = 96 K/W (free air) or R_th(j-sp) = 16 K/W (PCB-mounted) values.

Is BST39-QX pin-compatible with other SOT89 NPN transistors?

Yes, BST39-QX follows standard SOT89 pinout (1=E, 2=C, 3=B) and mechanical dimensions, making it physically compatible with other SOT89-packaged NPN transistors. However, electrical parameters-including V_CEO, h_FE, and f_T-differ significantly, so functional substitution requires validation against circuit requirements.

Does BST39-QX support PWM switching at frequencies above 1 MHz?

No-BST39-QX has a 70 MHz transition frequency (f_T), indicating usable gain drops sharply above ~10 MHz. For reliable PWM switching above 1 MHz, gate charge and switching speed become limiting; this device is optimized for <500 kHz operation in saturated switching or linear amplification roles.

How does the AEC-Q101 qualification impact BST39-QX usage in non-automotive designs?

AEC-Q101 qualification confirms enhanced reliability under temperature cycling, humidity, and mechanical stress-benefiting any mission-critical or long-lifecycle application. While not required outside automotive, it provides measurable margin in industrial controls, medical power supplies, and outdoor equipment where field failure risk must be minimized.

BST39-QX Specifications

Product attributes: Attribute value

Manufacturer:: Nexperia USA Inc.

Series:: -

Package/Case:: TO-243AA

Packaging:: Tape & Reel (TR)

Product Status:: Active

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 100 mA

Voltage - Collector Emitter Breakdown (Max):: 350 V

Vce Saturation (Max) @ Ib, Ic:: 500mV @ 4mA, 50mA

Current - Collector Cutoff (Max):: 20nA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 40 @ 20mA, 10V

Power - Max:: 1.3 W

Frequency - Transition:: 70MHz

Operating Temperature:: 150°C (TJ)

Grade:: Automotive

Qualification:: AEC-Q101

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-89

BST39-QX FAQ

1.How can I place an order for BST39-QX through Aetrix?

Please submit a Request for Quotation (RFQ) for BST39-QX 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 BST39-QX reliable?

The price and inventory of BST39-QX are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BST39-QX is usually 5 days.

3.What payment methods are accepted for BST39-QX?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BST39-QX transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BST39-QX?

BST39-QX orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BST39-QX 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 BST39-QX?

For technical support, including BST39-QX datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BST39-QX requirements.

6.How does Aetrix verify that BST39-QX is sourced from the original manufacturer or authorized distributors?

All BST39-QX 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 BST39-QX meets industry standards.

7.What is the process for return or replacement of BST39-QX?

All BST39-QX units undergo pre-shipment inspection (PSI). If there is an issue with BST39-QX, 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 BST39-QX part is unused and in its original packaging.

Return procedure for BST39-QX:

1.Submit a request within 90 days.

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

Tech Hub

2026-09-03 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…

2026-09-01 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…

2026-08-18 Operational Amplifier (Op Amp): Basics, Configurations, Feedback and Applications

Operational amplifier guide covering op amp basics, feedback, ideal vs real op amps, common configurations, buffer circuits, offset, bias current, gain-bandwidth, slew rate, rail-to-rail limits and sel…

2026-08-14 Jumper Cables: How to Use, Connect and Choose Them Safely

Jumper cables guide covering safe connection order, red and black clamp placement, final ground connection, cable gauge, length, clamp quality, copper vs CCA cables, jump starter comparison and battery…