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

onsemi BCP51

Name: BCP51
Brand: onsemi
SKU: BCP51
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BCP51

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-261-4, TO-261AA

Datasheet:: BCP51.pdf

Description:: TRANS PNP 45V 1.5A SOT-223-4

Quantity:: RFQ Add To RFQ list

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Inventory:3,000

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Product details

Overview

BCP51 from Fairchild Semiconductor is a PNP general-purpose amplifier transistor rated for -45 V V_CEO, -1.5 A continuous collector current, and 1.0 W power dissipation in SOT-223 package; it operates across -55°C to +150°C and is used in medium-power linear amplification and switching circuits such as audio preamplifiers and relay drivers.

For engineers reviewing the BCP51 datasheet, pinout, applications, or equivalent options, key selection criteria include its verified PNP polarity, guaranteed h_FE range of 25–250 at multiple bias points, V_CE(sat) ≤ -0.5 V at I_C = -500 mA / I_B = -50 mA, thermal resistance of 125°C/W on FR-4 PCB, and SOT-223 mechanical compatibility with standard surface-mount assembly processes.

Technical Context

The BCP51 is a silicon planar epitaxial PNP bipolar junction transistor optimized for medium-power analog amplification and saturated switching. Its DC current gain (h_FE) is specified across three operating points: 25–250 at I_C = -5 mA, 40–250 at I_C = -150 mA, and 25–250 at I_C = -500 mA - confirming stable gain behavior under varying load conditions.

It features symmetrical breakdown ratings: V_(BR)CEO = V_(BR)CBO = -45 V at specified test currents, and V_(BR)EBO = -5.0 V, supporting robust reverse-bias tolerance in emitter-follower or level-shifting configurations. Thermal performance is defined for FR-4 PCB mounting with ≥6 cm² collector pad area.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	-45 V - maximum safe collector-emitter voltage before breakdown in common-emitter configuration
I_C (continuous)	-1.5 A - maximum DC collector current sustainable without thermal runaway on specified PCB layout
P_D	1.0 W - total power dissipation limit at T_A = 25°C, derating 8.0 mW/°C above ambient
h_FE	25–250 - DC current gain range validated at I_C = -5 mA, -150 mA, and -500 mA with V_CE = -2.0 V
V_CE(sat)	≤ -0.5 V - guaranteed saturation voltage at I_C = -500 mA and I_B = -50 mA, enabling low-loss switching
R_θJA	125 °C/W - junction-to-ambient thermal resistance measured on FR-4 board with 6 cm² collector copper pad

Pinout & Package

SOT-223 package with 4-pin outline (pin 4 is tab/collector thermal pad); lead-free and RoHS-compliant per Fairchild specification.

Pin/Terminal	Circuit Role	Design Meaning
1	Base	Control terminal for forward-biased PNP operation; requires negative base current relative to emitter to turn on
2	Collector	Main current-carrying terminal; electrically and thermally connected to exposed metal tab (pin 4)
3	Emitter	Reference terminal for biasing; typically tied to higher potential in PNP circuits
4	Collector Tab	Thermal and electrical extension of collector; must be soldered to PCB copper pour for thermal management

Key Features

Feature	Design Value
Medium-power PNP architecture	Supports linear amplification up to 1.5 A and switching loads requiring controlled saturation and gain stability
Guaranteed h_FE spread across operating range	Enables predictable biasing in both small-signal and power stages without gain binning
V_CE(sat) ≤ -0.5 V @ I_C/I_B = -500/-50 mA	Reduces conduction loss and self-heating in high-duty-cycle switch applications
SOT-223 thermal pad (pin 4)	Provides direct thermal path to PCB; enables 1.0 W dissipation with minimal heatsinking on standard FR-4

Applications

Audio Preamp Stage	DC Motor Direction Control
Use Scenario: Low-noise, medium-gain voltage amplification in battery-powered portable audio front-ends. IC Role / Device Role / Timing Role: PNP transistor configured in common-emitter topology to provide inverted signal gain with stable h_FE across supply variations. Use Value: Delivers consistent -45 V breakdown margin and ≤ -0.5 V V_CE(sat) to minimize distortion and thermal drift in Class-A biased stages.	Use Scenario: H-bridge half-bridge leg driving brushed DC motors in industrial actuators. IC Role / Device Role / Timing Role: High-current PNP switch controlling motor current direction via complementary NPN/PNP pair. Use Value: Supports -1.5 A continuous collector current and 125°C/W thermal resistance, enabling reliable operation without forced air cooling.
Relay Driver Circuit	Voltage Level Shifter
Use Scenario: Driving 12 V/500 mA electromagnetic relays from 3.3 V or 5 V microcontroller GPIOs. IC Role / Device Role / Timing Role: Saturated PNP switch interfacing logic-level control signals to higher-voltage, higher-current loads. Use Value: Achieves deep saturation (V_CE(sat) ≤ -0.5 V) with modest base drive, reducing power loss and ensuring clean relay coil de-energization.	Use Scenario: Translating logic signals between -5 V reference domains and 0 V–3.3 V digital systems. IC Role / Device Role / Timing Role: Emitter-follower configured PNP device providing bidirectional level translation with minimal propagation delay. Use Value: Leverages -5.0 V V_(BR)EBO and symmetric -45 V breakdown ratings to safely handle reverse-biased transitions during domain crossing.

Audio Preamp Stage

DC Motor Direction Control

Use Scenario: Low-noise, medium-gain voltage amplification in battery-powered portable audio front-ends.

IC Role / Device Role / Timing Role: PNP transistor configured in common-emitter topology to provide inverted signal gain with stable h_FE across supply variations.

Use Value: Delivers consistent -45 V breakdown margin and ≤ -0.5 V V_CE(sat) to minimize distortion and thermal drift in Class-A biased stages.

Use Scenario: H-bridge half-bridge leg driving brushed DC motors in industrial actuators.

IC Role / Device Role / Timing Role: High-current PNP switch controlling motor current direction via complementary NPN/PNP pair.

Use Value: Supports -1.5 A continuous collector current and 125°C/W thermal resistance, enabling reliable operation without forced air cooling.

Relay Driver Circuit

Voltage Level Shifter

Use Scenario: Driving 12 V/500 mA electromagnetic relays from 3.3 V or 5 V microcontroller GPIOs.

IC Role / Device Role / Timing Role: Saturated PNP switch interfacing logic-level control signals to higher-voltage, higher-current loads.

Use Value: Achieves deep saturation (V_CE(sat) ≤ -0.5 V) with modest base drive, reducing power loss and ensuring clean relay coil de-energization.

Use Scenario: Translating logic signals between -5 V reference domains and 0 V–3.3 V digital systems.

IC Role / Device Role / Timing Role: Emitter-follower configured PNP device providing bidirectional level translation with minimal propagation delay.

Use Value: Leverages -5.0 V V_(BR)EBO and symmetric -45 V breakdown ratings to safely handle reverse-biased transitions during domain crossing.

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP medium-power amplifier and switching applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BCP52	V_CEO = -60 V (vs. -45 V), otherwise identical pinout, gain, and thermal specs	Preferred where higher off-state voltage margin is required, e.g., 24 V industrial bus interfaces	Select BCP52 when system transients exceed 45 V but same thermal and gain behavior is needed
MJD2955	TO-220 package, higher I_C = -12 A, R_θJA = 3°C/W (with heatsink), not SOT-223 compatible	Used in high-current linear regulators or motor drivers needing >1.5 A and active heatsinking	Choose MJD2955 only when board space allows TO-220 and thermal design includes heatsink

Compared with BCP52 and MJD2955, the BCP51 offers optimal balance of voltage rating, current capability, and SOT-223 surface-mount integration for space-constrained medium-power designs - neither over-specified nor thermally compromised.

Availability

BCP51 is available at Aetrix Electronics and suitable for audio preamplifiers, relay driver circuits, and DC motor direction control requiring stable component supply, long-term manufacturability, and consistent parametric performance across production lots.

Supply support for BCP51 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 designer and manufacturer of analog and discrete semiconductors, acquired by ON Semiconductor in 2016; known for high-reliability power and signal products.

The BCP51 belongs to Fairchild's general-purpose bipolar transistor family designed specifically for cost-sensitive, medium-power linear amplification and switching applications in consumer, industrial, and automotive auxiliary systems.

FAQ

What is the maximum collector-emitter voltage rating for the BCP51?

The BCP51 has a maximum collector-emitter voltage rating (V_CEO) of -45 V, verified under test condition I_C = -10 mA and I_B = 0 at T_A = 25°C. This rating applies to common-emitter configuration and reflects the device's ability to block reverse voltage without breakdown. Exceeding -45 V risks permanent degradation of the BCP51 junction integrity.

Does the BCP51 support surface-mount reflow assembly?

Yes, the BCP51 uses the SOT-223 package with standardized footprint and lead finish compatible with industry-standard lead-free reflow profiles. Its pin 4 thermal tab requires adequate solder paste volume and stencil aperture design to ensure void-free attachment to the PCB copper pour, which is essential for achieving the specified 125°C/W R_θJA.

What is the guaranteed DC current gain range for the BCP51 at I_C = -500 mA?

At I_C = -500 mA, V_CE = -2.0 V, and T_A = 25°C, the BCP51 guarantees an h_FE range of 25 to 250. This wide but bounded gain window ensures predictable bias point stability across production units and supports both linear amplification and saturated switching without requiring gain binning or external feedback compensation.

Can the BCP51 be used in parallel configurations for higher current handling?

No - the BCP51 is not characterized or recommended for paralleling due to inherent h_FE and V_BE(on) mismatches across units, which cause current imbalance and thermal runaway. For higher current needs, use a single higher-rated device like the MJD2955 or implement active current-sharing circuitry; the BCP51 should be deployed as a discrete switching or amplification element.

Is the BCP51 suitable for automotive applications?

The BCP51 meets AEC-Q101 stress test requirements per Fairchild's qualification report and operates across -55°C to +150°C junction temperature range, making it suitable for under-hood and cabin-located automotive auxiliary functions - including body control module relay drivers and HVAC blower motor controls - provided board-level thermal design adheres to the specified FR-4 mounting conditions.

BCP51 Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-261-4, TO-261AA

Packaging:: Bulk

Product Status:: Active

Transistor Type:: PNP

Current - Collector (Ic) (Max):: 1.5 A

Voltage - Collector Emitter Breakdown (Max):: 45 V

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

Current - Collector Cutoff (Max):: 100nA (ICBO)

DC Current Gain (hFE) (Min) @ Ic, Vce:: 40 @ 150mA, 2V

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

BCP51 FAQ

1.How can I place an order for BCP51 through Aetrix?

Please submit a Request for Quotation (RFQ) for BCP51 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 BCP51 reliable?

The price and inventory of BCP51 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BCP51 is usually 5 days.

3.What payment methods are accepted for BCP51?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BCP51 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BCP51?

BCP51 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BCP51 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 BCP51?

For technical support, including BCP51 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BCP51 requirements.

6.How does Aetrix verify that BCP51 is sourced from the original manufacturer or authorized distributors?

All BCP51 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 BCP51 meets industry standards.

7.What is the process for return or replacement of BCP51?

All BCP51 units undergo pre-shipment inspection (PSI). If there is an issue with BCP51, 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 BCP51 part is unused and in its original packaging.

Return procedure for BCP51:

1.Submit a request within 90 days.

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

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