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

onsemi BDX34B

Name: BDX34B
Brand: onsemi
SKU: BDX34B
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BDX34B

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-220-3

Datasheet:: BDX34B.pdf

Description:: TRANS PNP DARL 80V 10A TO-220

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Product details

Overview

BDX34B from onsemi is a PNP silicon Darlington power transistor in TO-220 package, rated for 80 V_CEO(sus), 10 A continuous collector current, and 70 W dissipation at T_C = 25°C, used in low-speed switching and linear regulator applications requiring high DC current gain (h_FE = 750 min at I_C = 3.0 A).

For engineers reviewing the BDX34B datasheet, pinout, applications, or equivalent options, this page delivers verified electrical parameters, thermal derating behavior, safe operating area limits, base-emitter shunt resistor integration, and direct alternatives for industrial power control designs.

Technical Context

The BDX34B employs monolithic Darlington construction with built-in base-emitter shunt resistors to reduce external component count and improve turn-off reliability. Its V_CE(sat) ≤ 2.5 V at I_C = 3.0 A and I_B = 6.0 mA enables efficient low-speed switching in relay drivers and motor controls.

Thermal design is constrained by R_JC = 1.78 °C/W and power derating to zero at T_C = 165°C, while second-breakdown-limited SOA curves define maximum I_C–V_CE combinations for single-pulse and DC operation below rated V_CEO.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO(sus)	80 Vdc minimum - sustains 80 V across C–E at 100 mA with zero base drive, defining absolute blocking capability in switching circuits
I_C Continuous	10 Adc - supports sustained load currents up to 10 A with heatsink at T_C ≤ 25°C
P_D @ T_C = 25°C	70 W - maximum steady-state power dissipation before thermal derating begins
h_FE	750 minimum at I_C = 3.0 A, V_CE = 3.0 V - enables low-base-drive switching with ~4 mA required to saturate 3 A load
V_CE(sat)	2.5 Vdc maximum at I_C = 3.0 A, I_B = 6.0 mA - sets conduction loss floor of 7.5 W per 3 A load
R_JC	1.78 °C/W - defines junction-to-case thermal resistance; requires ≥1.78 °C/W heatsink thermal path for full 70 W operation

Pinout & Package

BDX34B uses TO-220 package (Case 221A, Style 1), with metal tab electrically connected to collector. Mounting surface must be isolated unless collector is at system ground potential.

Pin/Terminal	Circuit Role	Design Meaning
1 (Base)	Control input	Accepts base current to enable Darlington pair; internal shunt resistor aids turn-off
2 (Collector)	High-side power node	Connected to metal tab; must be electrically isolated from heatsink unless referenced to system ground
3 (Emitter)	Current return path	Serves as common emitter for PNP operation; voltage drop determines load-side reference point

Key Features

Feature	Design Value
Monolithic Darlington with integrated base-emitter shunt resistor	Eliminates need for external turn-off resistor; reduces PCB footprint and improves switching consistency
High h_FE (750 min)	Enables direct drive from microcontroller GPIO or logic-level signals without intermediate buffer stage
80 V_CEO(sus) rating	Supports 24 V and 48 V industrial bus systems with margin against transients and inductive kickback
TO-220 mechanical robustness	Rated for >10,000 thermal cycles; compatible with standard clip-on heatsinks and automated through-hole assembly

Applications

Relay Driver Circuit	DC Motor Speed Control
Use Scenario: Driving 12–48 V electromagnetic relays with coil currents up to 8 A in PLC output modules. IC Role / Device Role / Timing Role: PNP Darlington switch providing high-current sinking path to ground when base is pulled low. Use Value: 750× current gain allows TTL/CMOS-compatible base drive; 2.5 V_CE(sat) limits relay coil voltage drop to <10% at full load.	Use Scenario: Linear speed regulation of brushed DC motors in HVAC actuators and industrial valves. IC Role / Device Role / Timing Role: Series pass element in emitter-follower configuration, dissipating variable power based on duty cycle. Use Value: 70 W thermal rating supports continuous 5 A motor current at 10 V drop; SOA curves validate safe operation under stall conditions.
Linear Voltage Regulator	High-Current LED Dimming
Use Scenario: Adjustable 3–30 V, 0–5 A bench power supply using LM317-based feedback loop. IC Role / Device Role / Timing Role: Pass transistor delivering regulated output; base driven by error amplifier to maintain setpoint. Use Value: Low V_BE(on) (≤2.5 V) minimizes dropout; built-in shunt resistor prevents latch-up during transient overloads.	Use Scenario: Constant-current dimming of high-brightness LED strings (e.g., 24 V, 3 A) in signage and architectural lighting. IC Role / Device Role / Timing Role: Current-sinking switch controlled by PWM signal applied to base via optocoupler or DAC. Use Value: 10 A continuous rating accommodates 3 A LED load with 2.3× safety margin; 80 V rating covers surge protection requirements.

Relay Driver Circuit

DC Motor Speed Control

Use Scenario: Driving 12–48 V electromagnetic relays with coil currents up to 8 A in PLC output modules.

IC Role / Device Role / Timing Role: PNP Darlington switch providing high-current sinking path to ground when base is pulled low.

Use Value: 750× current gain allows TTL/CMOS-compatible base drive; 2.5 V_CE(sat) limits relay coil voltage drop to <10% at full load.

Use Scenario: Linear speed regulation of brushed DC motors in HVAC actuators and industrial valves.

IC Role / Device Role / Timing Role: Series pass element in emitter-follower configuration, dissipating variable power based on duty cycle.

Use Value: 70 W thermal rating supports continuous 5 A motor current at 10 V drop; SOA curves validate safe operation under stall conditions.

Linear Voltage Regulator

High-Current LED Dimming

Use Scenario: Adjustable 3–30 V, 0–5 A bench power supply using LM317-based feedback loop.

IC Role / Device Role / Timing Role: Pass transistor delivering regulated output; base driven by error amplifier to maintain setpoint.

Use Value: Low V_BE(on) (≤2.5 V) minimizes dropout; built-in shunt resistor prevents latch-up during transient overloads.

Use Scenario: Constant-current dimming of high-brightness LED strings (e.g., 24 V, 3 A) in signage and architectural lighting.

IC Role / Device Role / Timing Role: Current-sinking switch controlled by PWM signal applied to base via optocoupler or DAC.

Use Value: 10 A continuous rating accommodates 3 A LED load with 2.3× safety margin; 80 V rating covers surge protection requirements.

Equivalent & Alternatives

The following parts are listed as comparable options for similar PNP Darlington power transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJD44H11T4G	Higher V_CEO = 100 V, lower h_FE = 1000 min, SOT-223 package (1.5 W P_D)	Not suitable for >1.5 W continuous dissipation; limited to low-power switching	Select only for space-constrained, low-current (<0.5 A) replacements where thermal budget permits
BDX34C	Same TO-220 package and Darlington architecture, but rated V_CEO(sus) = 100 V (vs. 80 V for BDX34B)	Direct upgrade path for designs requiring higher voltage margin without layout change	Choose BDX34C when operating bus voltage exceeds 60 V or transient immunity >20 V is required

Compared with MJD44H11T4G, BDX34B provides 46× higher power handling and 5× higher current capability; compared with BDX34C, it trades 20 V blocking margin for cost and availability advantages in 24–48 V systems.

Availability

BDX34B is available at Aetrix Electronics and suitable for relay driver circuits, linear voltage regulators, and DC motor control applications requiring stable component supply and long-term industrial lifecycle support.

Supply support for BDX34B 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier focused on energy-efficient power, analog, sensor, and connectivity solutions for automotive, industrial, cloud, and IoT markets.

The BDX34B belongs to onsemi's legacy silicon power transistor family designed specifically for ruggedized, low-speed switching and linear power control in industrial automation, power supplies, and electromechanical interfaces.

FAQ

What is the maximum continuous collector current rating for BDX34B?

The BDX34B is rated for 10 A continuous collector current (I_C) at case temperature T_C = 25°C. This rating decreases linearly above 25°C at 0.56 W/°C derating, reaching zero at approximately T_C = 165°C. Actual usable current depends on heatsink performance and ambient conditions.

Does BDX34B have an integrated base-emitter shunt resistor?

Yes, the BDX34B features monolithic construction with a built-in base-emitter shunt resistor. This resistor improves turn-off speed and prevents unintended conduction due to leakage currents, eliminating the need for an external pull-down resistor in most switching applications.

What is the collector-emitter sustaining voltage (V_CEO(sus)) specification for BDX34B?

The BDX34B has a minimum collector-emitter sustaining voltage V_CEO(sus) of 80 Vdc at I_C = 100 mAdc and I_B = 0. This parameter defines the maximum voltage the device can block in open-base switching configurations and is validated per JEDEC test conditions.

Can BDX34B be used as a direct replacement for BDX34C?

No, BDX34B is not a direct replacement for BDX34C due to its lower 80 V V_CEO(sus) rating versus BDX34C's 100 V rating. While both share identical pinout and package, substituting BDX34B in a BDX34C-design may compromise voltage margin in 72 V or higher transient environments.

What package type does BDX34B use and how is the collector terminal connected?

BDX34B uses the TO-220 package (Case 221A, Style 1), where pin 2 and the metal mounting tab are internally connected to the collector. This requires electrical isolation of the heatsink unless the collector node is tied to system ground, as confirmed in the official onsemi mechanical drawings.

BDX34B Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-220-3

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: PNP - Darlington

Current - Collector (Ic) (Max):: 10 A

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

Vce Saturation (Max) @ Ib, Ic:: 2.5V @ 6mA, 3A

Current - Collector Cutoff (Max):: 500µA

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

Power - Max:: 70 W

Frequency - Transition:: -

Operating Temperature:: -65°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220

BDX34B FAQ

1.How can I place an order for BDX34B through Aetrix?

Please submit a Request for Quotation (RFQ) for BDX34B 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 BDX34B reliable?

The price and inventory of BDX34B are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BDX34B is usually 5 days.

3.What payment methods are accepted for BDX34B?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BDX34B transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BDX34B?

BDX34B orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BDX34B 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 BDX34B?

For technical support, including BDX34B datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BDX34B requirements.

6.How does Aetrix verify that BDX34B is sourced from the original manufacturer or authorized distributors?

All BDX34B 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 BDX34B meets industry standards.

7.What is the process for return or replacement of BDX34B?

All BDX34B units undergo pre-shipment inspection (PSI). If there is an issue with BDX34B, 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 BDX34B part is unused and in its original packaging.

Return procedure for BDX34B:

1.Submit a request within 90 days.

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

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