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Diodes Incorporated BST39TA
- Part No.:
- BST39TA
- Manufacturer:
- Diodes Incorporated
- Category:
- Single Bipolar Transistors
- Package:
- TO-243AA
- Datasheet:
-
BST39TA.pdf
- Description:
- TRANS NPN 350V 0.5A SOT-89-3
- Quantity:
- Payment:
- Shipping:
Inventory:13,385
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Product details
Overview
BST39TA from Diodes Incorporated is a 350V NPN high-voltage transistor in SOT89 package, designed for switching and amplification in high-voltage DC-DC converters, flyback controllers, and industrial power supplies. It delivers 500mA continuous collector current, supports 1A peak pulse current, exhibits hFE ≥40 at IC = 20mA/VCE = 10V, and features VCE(sat) ≤0.5V at IC = 50mA/IB = 4mA.
For engineers reviewing the BST39TA datasheet, BST39TA pinout, BST39TA application, or BST39TA equivalent, key selection criteria include its 350V VCEO rating, thermal resistance of 125°C/W (15mm × 15mm copper), SOT89 lead-frame thermal performance, and suitability for non-automotive industrial switching where high BVCEO and stable hFE hold-up are required.
Technical Context
The BST39TA operates as a general-purpose NPN bipolar junction transistor optimized for medium-power, high-voltage switching. Its 400V VCBO and 350V VCEO ratings enable use in circuits with elevated collector potentials, while its 70MHz fT supports moderate-frequency switching up to several hundred kHz.
Thermal design relies on the exposed collector pad in SOT89: RθJL = 22°C/W and RθJC = 16°C/W confirm direct heat conduction paths, and derating curves show usable power dissipation down to 0.5W at +100°C ambient when mounted on 15mm × 15mm 1oz copper.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| VCEO | 350V - Enables safe operation in 277VAC-derived bus rails and 300V+ DC intermediate stages. |
| IC (continuous) | 500mA - Supports load currents up to 0.5A in discrete switch-mode power stage designs. |
| hFE | ≥40 @ IC=20mA - Ensures reliable base drive margin for low-gain control circuits without excessive IB overhead. |
| VCE(sat) | ≤0.5V @ IC=50mA/IB=4mA - Limits conduction loss to <25mW at 50mA, critical for efficiency in linear or quasi-resonant topologies. |
| fT | 70MHz - Allows stable switching up to ~300kHz with adequate gain margin in self-oscillating or PWM-controlled applications. |
| RθJA | 125°C/W (15mm×15mm 1oz FR4) - Defines minimum PCB copper area needed to maintain TJ <150°C at full PD = 1W. |
Pinout & Package
Package: SOT89 - Molded plastic package with exposed collector pad for enhanced thermal dissipation; RoHS-compliant, halogen-free, weight ≈0.072g.
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| Collector (C) | Main current output terminal | Exposed metal pad - must be soldered to ≥15mm² copper pour for rated thermal performance. |
| Emitter (E) | Current return path to ground/reference | Low-inductance connection point; referenced to system common in switching node layouts. |
| Base (B) | Control input for transistor biasing | Requires current-limited drive (e.g., series resistor) to ensure IB ≤4mA for saturation at 50mA IC. |
Key Features
| Feature | Design Value |
|---|---|
| High voltage blocking | 350V VCEO rating enables direct use in 277VAC offline SMPS primary-side switching without cascading devices. |
| Stable current gain | hFE ≥40 maintained across IC = 1–100mA range - reduces base drive variability in production systems. |
| Thermally robust lead frame | Exposed collector pad with RθJL = 22°C/W - allows efficient heat transfer to PCB without heatsink in ≤1W applications. |
| ESD resilience | 4kV HBM rating - withstands handling and board-level assembly without additional protection circuitry. |
Applications
| Industrial Power Supply | LED Driver Circuit |
|---|---|
Use Scenario: Discrete switch in 30W flyback converter for factory automation sensors. IC Role / Device Role / Timing Role: Main switching transistor controlling energy transfer during primary-side duty cycle. Use Value: 350V VCEO safely handles reflected 320V spikes from transformer leakage inductance under line surge conditions. |
Use Scenario: Constant-current switch in isolated LED driver for street lighting. IC Role / Device Role / Timing Role: Linear or PWM-controlled current regulator in secondary-side feedback loop. Use Value: Stable hFE ≥40 ensures predictable current scaling across temperature, minimizing LED brightness drift. |
| AC-DC Adapter | Capacitor Discharge Circuit |
Use Scenario: High-voltage start-up circuit in 12V/2A wall adapter. IC Role / Device Role / Timing Role: Auxiliary transistor charging bulk capacitor before controller IC activation. Use Value: 400V VCBO prevents breakdown during initial AC rectified peak (≈375V) before regulation engages. |
Use Scenario: Energy dump switch in photoflash or pulse-forming network. IC Role / Device Role / Timing Role: Fast turn-off device discharging high-voltage capacitor banks. Use Value: 1A ICM rating supports single-shot discharge pulses up to 500µs without second breakdown. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar high-voltage NPN transistor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ZTX653 | VCEO = 300V, hFE = 100–300 (higher gain but lower voltage) | Not suitable for >300V bus applications; requires redesign if VCE exceeds 300V | Select only when gain consistency matters more than voltage headroom and board space permits larger SOT223 package. |
| MJD112 | VCEO = 100V, IC = 2A, TO-252 package (lower voltage, higher current) | Cannot replace BST39TA in >100V circuits; requires complete topology revision | Use only in low-voltage, high-current linear regulators or motor drivers where thermal mass outweighs voltage limits. |
Compared with ZTX653 and MJD112, BST39TA uniquely balances 350V blocking capability with SOT89 thermal efficiency and moderate gain-making it irreplaceable in compact, medium-voltage industrial switchers where both voltage margin and PCB real estate are constrained.
Availability
BST39TA is available at Aetrix Electronics and suitable for industrial power supplies, LED drivers, and AC-DC adapters requiring stable component supply, long-term manufacturability, and RoHS-compliant sourcing.
Supply support for BST39TA 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
Diodes Incorporated is a global manufacturer of discrete semiconductors and analog ICs, headquartered in Plano, Texas, with design, manufacturing, and sales operations across Asia, Europe, and North America.
The BST39TA belongs to Diodes' high-voltage bipolar transistor product line, engineered specifically for cost-sensitive, thermally constrained industrial power conversion where reliability at elevated voltages is mandatory.
FAQ
Is BST39TA qualified for automotive applications?
No. BST39TA is not AEC-Q101 qualified and lacks PPAP documentation or IATF 16949-certified production traceability. Diodes explicitly states that automotive-grade variants require direct contact with their sales team for change-controlled versions-this part is intended for industrial and commercial use only.
What is the maximum allowable PCB copper area for thermal optimization?
The datasheet defines three thermal test conditions: 15mm × 15mm (RθJA = 125°C/W), 25mm × 25mm (83°C/W), and 50mm × 50mm (60°C/W). No upper limit is specified, but increasing copper beyond 50mm × 50mm yields diminishing returns; practical layout uses 25–30mm² for 1W operation at +70°C ambient.
Can BST39TA be used in linear regulator configurations?
Yes, but with strict thermal limits. At IC = 500mA and VCE = 10V, PD = 5W exceeds its 1W rating. Safe linear operation requires VCE × IC ≤ 1W - e.g., 2V × 500mA or 5V × 200mA - and mandatory use of ≥25mm × 25mm copper to sustain junction temperature below 150°C.
Does BST39TA have built-in ESD protection diodes?
No. The BST39TA has no integrated ESD protection structures. Its 4kV HBM rating reflects inherent junction robustness under standardized test conditions-not functional on-chip clamping. External TVS or RC snubbers remain necessary for system-level ESD immunity in end equipment.
BST39TA Specifications
- Product attributes
- Attribute value
- Manufacturer:
- Diodes Incorporated
- Series:
- -
- Package/Case:
- TO-243AA
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Active
- Transistor Type:
- NPN
- Current - Collector (Ic) (Max):
- 500 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 W
- Frequency - Transition:
- 70MHz
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-89-3
BST39TA FAQ
1.How can I place an order for BST39TA through Aetrix?
Please submit a Request for Quotation (RFQ) for BST39TA 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 BST39TA reliable?
The price and inventory of BST39TA are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BST39TA is usually 5 days.
3.What payment methods are accepted for BST39TA?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BST39TA transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for BST39TA?
BST39TA orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your BST39TA 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 BST39TA?
For technical support, including BST39TA datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BST39TA requirements.
6.How does Aetrix verify that BST39TA is sourced from the original manufacturer or authorized distributors?
All BST39TA 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 BST39TA meets industry standards.
7.What is the process for return or replacement of BST39TA?
All BST39TA units undergo pre-shipment inspection (PSI). If there is an issue with BST39TA, 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 BST39TA part is unused and in its original packaging.
Return procedure for BST39TA:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
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