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Nexperia USA Inc. BST39,115
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- Part No.:
- BST39,115
- Manufacturer:
- Nexperia USA Inc.
- Category:
- Single Bipolar Transistors
- Package:
- TO-243AA
- Datasheet:
-
BST39,115.pdf
- Description:
- TRANS NPN 350V 0.1A SOT-89
- Quantity:
- Payment:
- Shipping:
Inventory:9,974
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Product details
Overview
BST39 from Nexperia is an NPN high-voltage bipolar junction transistor in SOT89 (SC-62) package, designed for switching and amplification in circuits requiring up to 350 V collector-emitter voltage, 100 mA continuous collector current, and DC current gain ≥40 at 20 mA. It operates reliably across –65 °C to +150 °C ambient and is commonly used in flyback converter auxiliary supplies and HV signal conditioning stages.
For engineers reviewing the BST39 datasheet, BST39 pinout, BST39 application, or BST39 equivalent, key selection criteria include its 350 V VCEO, 1.3 W power dissipation on FR4 PCB, 70 MHz fT, low leakage (20 nA ICBO), and thermal resistance of 16 K/W to solder point - all critical for high-voltage discrete design validation.
Technical Context
The BST39 functions as a medium-speed, high-voltage NPN switch with fixed emitter-base and collector-base breakdown limits (VEBO = 5 V, VCBO = 400 V). Its DC current gain (hFE) is specified at VCE = 10 V and IC = 20 mA, and saturation voltage is confirmed at 500 mV under IC = 50 mA / IB = 4 mA conditions.
Thermal performance is defined for a standard FR4 PCB mount with 6 cm² collector pad: Rth(j–a) = 96 K/W (free air), Rth(j–sp) = 16 K/W (to solder point). Junction temperature is rated to 150 °C, and storage/ambient range spans –65 °C to +150 °C.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCEO | 350 V - Maximum safe collector-emitter voltage with base open; defines upper limit for off-state blocking in HV switching. |
| IC (continuous) | 100 mA - Continuous collector current rating; sets max steady-state load drive capability. |
| hFE | ≥40 - Minimum DC current gain at VCE = 10 V, IC = 20 mA; determines required base drive for saturation. |
| VCE(sat) | ≤500 mV - Collector-emitter voltage in saturation at IC = 50 mA / IB = 4 mA; impacts conduction loss in switching applications. |
| fT | 70 MHz - Transition frequency at VCE = 10 V, IC = 10 mA; indicates usable bandwidth for small-signal amplification. |
| Rth(j–sp) | 16 K/W - Thermal resistance from junction to solder point on FR4; enables thermal modeling of PCB-level heat transfer. |
| ICBO | ≤20 nA - Collector-base leakage at VCB = 300 V; critical for high-impedance bias stability in HV circuits. |
Pinout & Package
The BST39 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 collector thermal pad. The package is optimized for power dissipation on single-sided FR4 PCBs with tin-plated copper.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Emitter (E) | Current exit terminal; connected to ground or low-side reference in common-emitter configurations. |
| 2 | Collector (C) | Main current input terminal; electrically and thermally tied to large PCB copper area for heat dissipation. |
| 3 | Base (B) | Control terminal; requires ~4 mA drive for full saturation at 50 mA collector load. |
Key Features
| Feature | Design Value |
|---|---|
| High-voltage blocking | 350 V VCEO enables use in 230 VAC-derived auxiliary supplies without external snubbers. |
| Low leakage | 20 nA ICBO ensures stable biasing in high-impedance HV feedback networks. |
| Thermally enhanced SOT89 | 16 K/W Rth(j–sp) allows 1.3 W dissipation with minimal board area - no heatsink needed. |
| Medium-frequency response | 70 MHz fT supports linear amplification up to audio and low-RF frequencies. |
Applications
| Switch-Mode Power Supply Auxiliary Bias | Flyback Converter Startup Circuit |
|---|---|
Use Scenario: Provides isolated bias supply for PWM controller ICs in offline AC/DC converters. IC Role / Device Role / Timing Role: NPN switch driving transformer primary during startup; turns off once main supply reaches regulation. Use Value: Withstands 350 V transient spikes during no-load or light-load operation and delivers reliable turn-on with ≤500 mV VCE(sat). | Use Scenario: Enables controlled energy transfer from primary to secondary during initial power-up before feedback loop engages. IC Role / Device Role / Timing Role: High-voltage switch controlling gate drive to main power MOSFET via optocoupler-coupled timing network. Use Value: 400 V VCBO rating prevents breakdown during transformer ringing; 20 nA leakage avoids false triggering. |
| Industrial Sensor Signal Conditioning | AC Line Voltage Detection |
Use Scenario: Amplifies low-level analog signals from pressure or temperature transducers operating in noisy industrial environments. IC Role / Device Role / Timing Role: Common-emitter amplifier stage with fixed bias; provides gain ≥40 while rejecting common-mode noise. Use Value: Stable hFE over –65 °C to +150 °C ensures consistent gain across wide temperature ranges. | Use Scenario: Detects presence of 230 VAC line voltage using resistive divider and transistor-based zero-crossing interface. IC Role / Device Role / Timing Role: High-voltage level shifter converting rectified AC peaks into clean logic-compatible pulses. Use Value: 350 V VCEO safely handles peak line voltages (≈325 V); low ICBO prevents false detection during zero-crossing intervals. |
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 |
|---|---|---|---|
| BCW66G | VCEO = 60 V, IC = 800 mA, hFE = 100–630 - lower voltage, higher current, wider gain spread. | Not suitable for >100 V blocking; better for low-voltage, high-gain amplification. | Select only if operating voltage <60 V and higher hFE tolerance is acceptable. |
| BUV28A | VCEO = 450 V, IC = 2 A, TO-126 package - higher voltage/current, larger thermal mass. | Requires heatsink; overqualified for SOT89-space-constrained designs below 100 mA. | Choose when >350 V margin or >100 mA load is required; not drop-in due to package and footprint mismatch. |
Compared with BCW66G and BUV28A, the BST39 uniquely balances 350 V blocking, SOT89 thermal efficiency, and predictable hFE in compact form - making it optimal for cost-sensitive, space-limited HV auxiliary and sensing circuits where precise 100 mA/350 V operation is required.
Availability
BST39 is available at Aetrix Electronics and suitable for switch-mode power supply auxiliary bias, flyback startup circuits, industrial sensor signal conditioning, and AC line voltage detection requiring stable component supply and long-term industrial lifecycle support.
Supply support for BST39 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-performance, reliable discrete and logic devices, with leadership in automotive, industrial, and consumer power management solutions.
The BST39 belongs to Nexperia's high-voltage bipolar transistor product line, engineered specifically for robust, thermally efficient switching and amplification in offline power and industrial sensing applications.
FAQ
Is the BST39 automotive-qualified?
No. Per Nexperia's 2024 revision history, the BST39 is explicitly designated as non-automotive qualified. It lacks AEC-Q101 stress testing and is not warranted for automotive safety-critical systems. Automotive alternatives must be selected from Nexperia's dedicated -Q qualified portfolio.
What is the maximum allowable PCB copper area for thermal performance?
The datasheet specifies a 6 cm² single-sided, tin-plated copper mounting pad for the collector terminal to achieve the rated 1.3 W power dissipation and 16 K/W Rth(j–sp). Reducing pad area increases thermal resistance and reduces safe operating current.
Can the BST39 replace a BC548 in a 12 V circuit?
Yes - electrically, but not optimally. While the BST39 meets basic NPN functionality, its higher VCEO and lower hFE (min 40 vs. BC548's min 110) result in excessive base drive requirements and reduced gain margin. Use only if HV robustness or thermal performance is prioritized over gain.
Does the BST39 require a base resistor in switching applications?
Yes. To ensure saturation at IC = 50 mA, the datasheet confirms IB = 4 mA is required. A series base resistor must be sized to deliver this current from the driver voltage, accounting for VBE ≈ 0.7 V and driver output impedance.
BST39,115 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Nexperia USA Inc.
- Series:
- -
- Package/Case:
- TO-243AA
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Transistor Type:
- NPN
- 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
BST39,115 FAQ
1.How can I place an order for BST39,115 through Aetrix?
Please submit a Request for Quotation (RFQ) for BST39,115 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 BST39,115 reliable?
The price and inventory of BST39,115 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BST39,115 is usually 5 days.
3.What payment methods are accepted for BST39,115?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BST39,115 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for BST39,115?
BST39,115 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your BST39,115 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 BST39,115?
For technical support, including BST39,115 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BST39,115 requirements.
6.How does Aetrix verify that BST39,115 is sourced from the original manufacturer or authorized distributors?
All BST39,115 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 BST39,115 meets industry standards.
7.What is the process for return or replacement of BST39,115?
All BST39,115 units undergo pre-shipment inspection (PSI). If there is an issue with BST39,115, 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 BST39,115 part is unused and in its original packaging.
Return procedure for BST39,115:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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