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

STMicroelectronics BDX54B

Name: BDX54B
Brand: STMicroelectronics
SKU: BDX54B
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BDX54B

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-220-3

Datasheet:: BDX54B.pdf

Description:: TRANS PNP DARL 80V 8A TO-220

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BDX54B from STMicroelectronics is a PNP complementary power Darlington transistor in TO-220 package, featuring monolithic Darlington configuration with integrated antiparallel collector-emitter diode, V_CEO = 80 V, I_C = 8 A, h_FE ≥ 750 at I_C = 3 A, and used in linear audio output stages and industrial switching amplifiers.

For engineers reviewing the BDX54B datasheet, BDX54B pinout, BDX54B application, or BDX54B equivalent, key selection considerations include its PNP polarity, 60 W power dissipation at T_c = 25°C, integrated clamping diode, saturation voltage of 2 V at I_C = 3 A / I_B = 12 mA, and suitability for high-current linear amplification where thermal stability and gain linearity are critical.

Technical Context

The BDX54B implements a monolithic Darlington pair with built-in antiparallel emitter-collector diode for inductive load protection. Its planar base island technology ensures consistent h_FE linearity across operating current and supports stable DC biasing in Class AB audio output stages.

It operates as a high-gain, high-current PNP switch or linear amplifier with V_CEO(sus) = 80 V (pulsed), f_T optimized for audio-frequency response, and thermal design enabled by TO-220's low junction-to-case resistance (R_thJC ≈ 0.83°C/W implied by P_TOT = 60 W at T_c = 25°C).

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	80 V - Maximum safe collector-emitter voltage under open-base condition; defines rail voltage limit in linear amplifier designs.
I_C	8 A continuous - Sustained output current capability; enables ±30 V, 50 W audio amplifier output stages.
h_FE	≥750 at I_C = 3 A - High DC current gain reduces required driver stage current and simplifies bias network design.
V_CE(sat)	2 V at I_C = 3 A / I_B = 12 mA - Low saturation voltage minimizes conduction loss and heat generation in switching applications.
P_TOT	60 W at T_c = 25°C - Total power dissipation rating; requires heatsink with R_thSA ≤ 1.5°C/W for 100°C ambient operation.
V_F	1.8–2.5 V at I_F = 3–8 A - Forward voltage of integrated antiparallel diode; provides passive flyback protection for relay/inductor loads.

Pinout & Package

BDX54B is housed in a standard TO-220 package with three leads: Collector (pin 1), Base (pin 2), Emitter (pin 3), mounted on a metal tab thermally connected to the collector. The device uses planar base island fabrication and features an integrated antiparallel diode between collector and emitter.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1 (Tab)	Collector	Electrically and thermally connected to metal tab; must be isolated from heatsink unless circuit ground reference permits.
Pin 2	Base	Control input for Darlington pair; requires ~12 mA drive for full 3 A output saturation.
Pin 3	Emitter	Power return path; connects to positive rail in high-side switch or output node in PNP emitter-follower amplifier.

Key Features

Feature	Design Value
Monolithic Darlington structure	Single-die integration eliminates inter-device matching drift and improves thermal coupling between driver and output transistors.
Integrated antiparallel C–E diode	Eliminates need for external flyback diode in relay drivers and inductive load switches, reducing BOM count and PCB area.
Good h_FE linearity	Enables low-distortion Class AB audio output operation without complex feedback compensation networks.
High f_T	Supports stable gain up to mid-audio frequencies (~100 kHz typical), suitable for wideband linear amplifiers and fast-switching SMPS drivers.

Applications

Audio Power Amplifier Output Stage

Industrial Relay Driver

Use Scenario: Final output stage in discrete ±30 V, 50 W stereo amplifier delivering low-THD analog signal to 4–8 Ω speakers.

IC Role / Device Role / Timing Role: PNP Darlington output transistor providing high-current sourcing capability and precise DC bias control.

Use Value: h_FE ≥ 750 enables simple two-transistor driver stage; integrated diode prevents latch-up during speaker transient recovery.

Use Scenario: Driving 24 VDC, 2 A industrial relay coil with 100 ms switching cycles in PLC I/O modules.

IC Role / Device Role / Timing Role: High-current PNP switch controlling coil energization; integrated diode clamps inductive kickback.

Use Value: Eliminates external flyback diode; V_CE(sat) = 2 V limits power loss to <1.5 W at full load, easing thermal management.

Linear Voltage Regulator Pass Element

DC Motor H-Bridge Complementary Pair

Use Scenario: Series pass element in adjustable 0–24 V, 3 A linear regulator powering sensitive analog instrumentation.

IC Role / Device Role / Timing Role: PNP-controlled current source regulating output voltage via feedback loop; handles worst-case dropout and ripple rejection.

Use Value: 8 A I_C rating provides 2× safety margin; good h_FE linearity ensures stable loop gain across load range.

Use Scenario: Upper PNP switch in 24 V, 5 A brushed DC motor H-bridge for factory automation actuators.

IC Role / Device Role / Timing Role: High-side current source in complementary Darlington pair with BDX53B (NPN) for bidirectional motor control.

Use Value: Matched V_CEO/I_C ratings and TO-220 footprint enable symmetrical layout; integrated diode suppresses shoot-through transients.

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP power Darlington switching and linear amplification applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJD47	TO-252 (DPAK), V_CEO = 80 V, I_C = 4 A, no integrated diode	Suitable only for surface-mount designs with lower current demand; requires external flyback diode	Select when space-constrained PCB layout favors SMT and peak current ≤4 A
BDX54C	V_CEO = 100 V, otherwise identical pinout, package, and electrical behavior	Used where higher breakdown margin is needed against supply rail transients or in 48 V industrial systems	Select when system overvoltage risk exceeds 80 V; drop-in replacement with same thermal and drive requirements

Compared with MJD47 and BDX54C, the BDX54B offers unique value in through-hole, high-current (8 A), diode-integrated PNP Darlington operation - enabling robust, low-component-count designs in audio and industrial linear switching where reliability and thermal headroom are prioritized over miniaturization.

Availability

BDX54B is available at Aetrix Electronics and suitable for audio power amplifiers, industrial relay drivers, linear voltage regulators, and DC motor H-bridge circuits requiring stable component supply and long-term manufacturability.

Supply support for BDX54B 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

STMicroelectronics is a global semiconductor leader headquartered in Geneva, designing and manufacturing microcontrollers, power transistors, analog ICs, and MEMS sensors for industrial, automotive, and consumer markets.

The BDX54B belongs to ST's legacy power bipolar transistor family, engineered specifically for high-fidelity audio output stages and rugged industrial switching applications where monolithic integration, thermal robustness, and predictable gain behavior are essential.

FAQ

Is BDX54B RoHS-compliant and lead-free?

Yes, BDX54B is manufactured in ST's ECOPACK® package with lead-free second-level interconnect, compliant with RoHS Directive 2011/65/EU. The inner box label and package marking indicate the JEDEC JESD97-compliant eco-category, and soldering profiles follow ST's specified reflow guidelines for Pb-free assembly.

Can BDX54B be used in parallel configurations?

Yes, but only with emitter resistors (typically 0.1–0.22 Ω) to ensure current sharing. The monolithic Darlington structure provides better thermal tracking than discrete pairs, yet inherent parameter spread (h_FE, V_BE) still requires individual emitter degeneration for reliable parallel operation above 10 A total current.

What is the maximum safe operating area (SOA) limitation at 25°C case temperature?

At T_c = 25°C, BDX54B's SOA is bounded by I_C = 8 A (DC), V_CE = 80 V (second breakdown limit), and P_TOT = 60 W. For pulse operation (duty cycle ≤1.5%, t_p ≤ 300 µs), V_CEO(sus) = 80 V applies, but sustained operation above 40 V × 1.5 A violates SOA due to secondary breakdown risk.

Does the integrated diode support reverse recovery in high-frequency switching?

No - the integrated antiparallel diode is a slow, high-current junction diode (t_rr not specified; VF tested at DC), intended solely for clamping inductive turn-off transients below 10 kHz. It is unsuitable for high-frequency synchronous rectification or snubberless flyback converters operating >20 kHz.

BDX54B Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-220-3

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: PNP - Darlington

Current - Collector (Ic) (Max):: 8 A

Voltage - Collector Emitter Breakdown (Max):: 80 V

Vce Saturation (Max) @ Ib, Ic:: 2V @ 12mA, 3A

Current - Collector Cutoff (Max):: 500µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 750 @ 3A, 3V

Power - Max:: 60 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220

BDX54B FAQ

1.How can I place an order for BDX54B through Aetrix?

Please submit a Request for Quotation (RFQ) for BDX54B 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 BDX54B reliable?

The price and inventory of BDX54B are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BDX54B is usually 5 days.

3.What payment methods are accepted for BDX54B?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BDX54B transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BDX54B?

BDX54B orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BDX54B 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 BDX54B?

For technical support, including BDX54B datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BDX54B requirements.

6.How does Aetrix verify that BDX54B is sourced from the original manufacturer or authorized distributors?

All BDX54B 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 BDX54B meets industry standards.

7.What is the process for return or replacement of BDX54B?

All BDX54B units undergo pre-shipment inspection (PSI). If there is an issue with BDX54B, 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 BDX54B part is unused and in its original packaging.

Return procedure for BDX54B:

1.Submit a request within 90 days.

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

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