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onsemi BSP51
- Part No.:
- BSP51
- Manufacturer:
- onsemi
- Category:
- Single Bipolar Transistors
- Package:
- TO-261-4, TO-261AA
- Datasheet:
-
BSP51.pdf
- Description:
- TRANS NPN DARL 80V 0.5A SOT223-4
- Quantity:
- Payment:
- Shipping:
Inventory:9,304
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Product details
Overview
BSP51 from Fairchild Semiconductor is an NPN Darlington transistor optimized for high-current-switching applications up to 500 mA, featuring minimum DC current gain (hFE) of 1000 at IC = 150 mA and VCE = 10 V, VCE(sat) ≤ 1.3 V at IC = 500 mA/IB = 0.5 mA, and 80 V collector-emitter breakdown voltage - used in relay drivers, lamp drivers, and low-frequency power switching circuits.
For engineers reviewing the BSP51 datasheet, pinout, applications, or equivalent options, key selection criteria include guaranteed high hFE across operating current range, low saturation voltage under full-load drive, SOT-223 thermal performance (RθJA = 125°C/W on FR-4), and compatibility with standard 5 V logic-level base drive in discrete switching stages.
Technical Context
The BSP51 implements a monolithic NPN Darlington pair with integrated base-emitter resistor network absent - requiring external base current control. It operates as a single-stage high-gain current amplifier with two cascaded NPN junctions, enabling efficient switching at low base drive levels while maintaining safe SOA limits up to 500 mA continuous collector current.
Thermal design relies on the SOT-223 package's exposed collector tab for PCB heat spreading; derating begins above 25°C ambient at 8.0 mW/°C, with maximum junction temperature limited to +150°C. Electrical behavior is specified under pulse test conditions (≤300 μs, ≤2% duty cycle) for saturation parameters.
Key Specifications
| Parameter | Value and Actual Design Meaning |
|---|---|
| Device Type | NPN Darlington transistor - provides cascaded current gain for low-base-drive switching |
| VCES | 80 V - supports operation in 24–48 V industrial control rails without breakdown |
| IC (Continuous) | 500 mA - enables direct driving of medium-power loads like solenoids or LED arrays |
| hFE (min) | 1000 at IC = 150 mA - ensures reliable turn-on with ≤0.15 mA base current |
| VCE(sat) (max) | 1.3 V at IC = 500 mA/IB = 0.5 mA - limits conduction loss to <650 mW at full load |
| RθJA | 125°C/W on 1.6" × 1.6" FR-4 - defines thermal margin for ambient temperatures up to +70°C at full power |
Pinout & Package
SOT-223 package with molded plastic body, exposed collector thermal pad on underside, and three active terminals: Pin 1 = Base, Pin 2 = Collector (tab), Pin 3 = Emitter. Pin 4 is unused (thermal slug extension, not electrically connected).
| Pin/Terminal | Circuit Role | Design Meaning |
|---|---|---|
| 1 | Base | Input control terminal; requires current-limited drive (e.g., series resistor from 5 V MCU GPIO) |
| 2 | Collector | Main power output node; electrically tied to exposed metal tab for thermal conduction to PCB |
| 3 | Emitter | Common emitter reference; connects to system ground or load return path |
| 4 | Thermal Slug | Non-electrical mechanical interface; soldered to copper pour for thermal dissipation only |
Key Features
| Feature | Design Value |
|---|---|
| High DC Current Gain | hFE ≥ 1000 at 150 mA ensures robust switching with microcontroller-grade base drive |
| Low Saturation Voltage | VCE(sat) ≤ 1.3 V minimizes power loss and self-heating during sustained conduction |
| 80 V Breakdown Rating | Supports use in 24 V and 48 V industrial systems with margin against transients |
| SOT-223 Thermal Performance | 125°C/W RθJA enables >700 mW usable power dissipation on standard PCB layout |
Applications
| Relay Driver Stage | Lamp / LED Array Driver |
|---|---|
Use Scenario: Driving 24 V DC electromagnetic relays with coil resistance ~200 Ω in PLC I/O modules. IC Role / Device Role / Timing Role: High-gain current switch amplifying weak MCU GPIO signal to deliver ≥120 mA relay coil current. Use Value: Eliminates need for multi-stage BJT or MOSFET driver; single BSP51 achieves full relay actuation with 0.12 mA base current. | Use Scenario: Switching 12–24 V incandescent lamps or parallel white LED strings in building automation panels. IC Role / Device Role / Timing Role: Medium-current load switch handling peak currents up to 500 mA with minimal board space. Use Value: VCE(sat) ≤ 1.3 V limits lamp dimming due to voltage drop and reduces heatsink requirements. |
| Motor Start Assist Circuit | Industrial Solenoid Interface |
Use Scenario: Providing momentary high-current boost to starter windings of small DC motors in HVAC actuators. IC Role / Device Role / Timing Role: Short-duration (≤500 ms) current amplifier triggered by microcontroller PWM edge. Use Value: hFE ≥ 2000 at 500 mA allows precise timing control without base current overshoot or latch-up risk. | Use Scenario: Controlling 24 V DC solenoid valves in fluid control manifolds for factory automation. IC Role / Device Role / Timing Role: Robust on/off switch interfacing between logic-level controller and inductive load. Use Value: 90 V VCBO rating accommodates flyback spikes up to 60 V with external clamp diode. |
Equivalent & Alternatives
The following parts are listed as comparable options for similar NPN Darlington transistor applications.
| Alternative Part | Technical Difference | Application Difference | Selection Advice |
|---|---|---|---|
| ON Semiconductor NSS12500UW3T1G | Higher VCE(sat) (1.5 V min), lower hFE (500 min), SOT-323 package (lower power capability) | Not suitable for ≥400 mA loads; limited thermal margin on standard PCB | Select only for space-constrained, low-duty-cycle signal switching where 100 mA max load applies |
| Diodes Incorporated DXT511100Q-13 | Same SOT-223 footprint, higher VCES (100 V), identical hFE spec (1000 min), but VBE(sat) = 2.1 V (vs. 1.9 V) | Compatible drop-in replacement for higher-voltage rails; slightly higher base drive requirement | Preferred when system transient immunity >80 V is required and base drive headroom ≥2.1 V is available |
Compared with NSS12500UW3T1G, BSP51 delivers 5× higher current capability and superior thermal management; versus DXT511100Q-13, it offers lower base-emitter saturation voltage for tighter logic-level compatibility - making BSP51 optimal for 24–48 V industrial switching where both gain and efficiency matter.
Availability
BSP51 is available at Aetrix Electronics and suitable for relay drivers, lamp/LED array interfaces, motor start assist circuits, and industrial solenoid control requiring stable component supply and long-term industrial lifecycle support.
Supply support for BSP51 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
Fairchild Semiconductor was a U.S.-based analog and power semiconductor manufacturer, acquired by ON Semiconductor in 2016; known for high-reliability discrete devices and power management ICs.
The BSP51 belongs to Fairchild's legacy bipolar transistor family designed specifically for cost-sensitive, medium-current industrial switching - emphasizing manufacturability, thermal robustness, and compatibility with legacy 5 V logic systems.
FAQ
What is the maximum continuous collector current rating for the BSP51?
The BSP51 is rated for 500 mA continuous collector current (IC) at Ta = 25°C. Derating is required above 25°C ambient per the 8.0 mW/°C specification. At 70°C ambient, usable IC drops to approximately 360 mA to maintain TJ ≤ 150°C. This rating assumes proper PCB copper area for thermal conduction via the SOT-223 collector tab.
Does the BSP51 have an integrated base resistor?
No, the BSP51 does not include an integrated base resistor. It is a bare Darlington transistor requiring external base current limiting - typically a series resistor between the driving GPIO and Pin 1 (Base). This allows flexible biasing for varying load currents and ensures stable operation across temperature.
Can the BSP51 be used as a direct replacement for the MMBT51 in SOT-23 packages?
No, the BSP51 is not a direct replacement for MMBT51. The BSP51 uses SOT-223 packaging with different pinout (1=Base, 2=Collector, 3=Emitter), higher current capability (500 mA vs. 100 mA), and significantly higher hFE (1000+ vs. ~100). PCB layout, thermal design, and drive circuitry must be re-evaluated - it is not pin-compatible or functionally interchangeable without redesign.
What is the typical VBE(sat) of the BSP51 under full-load conditions?
The BSP51 exhibits a maximum VBE(sat) of 1.9 V at IC = 500 mA and IB = 0.5 mA. Typical values measured at room temperature fall near 1.7 V. This defines the minimum base drive voltage required - e.g., a 3.3 V MCU GPIO may require series resistance adjustment to ensure ≥0.5 mA base current while staying within safe VBE stress limits.
Is the BSP51 suitable for automotive applications?
The BSP51 is not AEC-Q101 qualified and lacks automotive-grade screening or extended temperature validation beyond −55°C to +150°C. While its absolute ratings meet some automotive subsystem requirements, Fairchild did not release automotive-specific qualification data for BSP51. For automotive use, consult AEC-Q101-qualified alternatives such as the NSV511100T1G or contact Aetrix for validated automotive-grade equivalents.
BSP51 Specifications
- Product attributes
- Attribute value
- Manufacturer:
- onsemi
- Series:
- -
- Package/Case:
- TO-261-4, TO-261AA
- Packaging:
- Tape & Reel (TR)
- Product Status:
- Obsolete
- Transistor Type:
- NPN - Darlington
- Current - Collector (Ic) (Max):
- 500 mA
- Voltage - Collector Emitter Breakdown (Max):
- 80 V
- Vce Saturation (Max) @ Ib, Ic:
- 1.3V @ 500µA, 500mA
- Current - Collector Cutoff (Max):
- 10µA
- DC Current Gain (hFE) (Min) @ Ic, Vce:
- 1000 @ 150mA, 10V
- Power - Max:
- 1 W
- Frequency - Transition:
- -
- Operating Temperature:
- -55°C ~ 150°C (TJ)
- Grade:
- -
- Qualification:
- -
- Mounting Type:
- Surface Mount
- Supplier Device Package:
- SOT-223-4
BSP51 FAQ
1.How can I place an order for BSP51 through Aetrix?
Please submit a Request for Quotation (RFQ) for BSP51 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 BSP51 reliable?
The price and inventory of BSP51 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BSP51 is usually 5 days.
3.What payment methods are accepted for BSP51?
We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BSP51 transactions.
Note: Certain payment methods may incur a processing fee.
4.How is shipping managed for BSP51?
BSP51 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.
Once your BSP51 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 BSP51?
For technical support, including BSP51 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BSP51 requirements.
6.How does Aetrix verify that BSP51 is sourced from the original manufacturer or authorized distributors?
All BSP51 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 BSP51 meets industry standards.
7.What is the process for return or replacement of BSP51?
All BSP51 units undergo pre-shipment inspection (PSI). If there is an issue with BSP51, 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 BSP51 part is unused and in its original packaging.
Return procedure for BSP51:
1.Submit a request within 90 days.
2.Obtain a Return Material Authorization (RMA) from Aetrix.
BSP51 Tags
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