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

STMicroelectronics BDX33C

Name: BDX33C
Brand: STMicroelectronics
SKU: BDX33C
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BDX33C

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

Package:: TO-220-3

Datasheet:: BDX33C.pdf

Description:: TRANS NPN DARL 100V 10A TO-220

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BDX33C from STMicroelectronics is a silicon NPN power Darlington transistor in TO-220 package, designed for high-current linear and switching applications. It features 100 V V_CEO, 10 A continuous collector current, 70 W total dissipation at T_c ≤ 25 °C, and DC current gain (h_FE) ≥ 750 at I_C = 3 A, V_CE = 3 V - used in motor control stages and audio output amplifiers.

For engineers reviewing the BDX33C datasheet, BDX33C pinout, BDX33C application, or BDX33C equivalent, key selection considerations include safe operating area (SOA) compliance at elevated case temperatures, Darlington base drive requirements (I_B ≤ 0.25 A), thermal resistance (R_thj-case = 1.78 °C/W), and complementary PNP pairing with BDX34C.

Technical Context

The BDX33C integrates two NPN transistors in monolithic Darlington configuration with built-in base-emitter resistors (R1 ≈ 10 kΩ, R2 ≈ 150 Ω), enabling simplified biasing and improved turn-on speed over single-stage power transistors. Its internal schematic supports direct TTL/CMOS-compatible drive without external base resistors.

It operates in both linear (e.g., Class AB audio output) and switching (e.g., DC motor H-bridge low-side) modes, with V_CE(sat) = 2.5 V at I_C = 3 A / I_B = 6 mA and parallel diode forward voltage V_F = 4 V at I_F = 8 A - critical for flyback energy handling in inductive loads.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	100 V - maximum sustainable collector-emitter voltage with base open; defines upper rail limit in 80–100 V power supplies.
I_C	10 A continuous - usable DC load current before thermal derating; supports 50–100 W audio amplifier outputs.
P_tot	70 W at T_c ≤ 25 °C - requires heatsink with thermal resistance ≤ 1.78 °C/W to maintain T_j ≤ 150 °C.
h_FE	≥ 750 at I_C = 3 A - enables low-base-drive-current operation (e.g., 4 mA drives 3 A load), reducing driver stage complexity.
R_thj-case	1.78 °C/W - quantifies junction-to-case thermal path; determines minimum heatsink size for given ambient and power dissipation.
V_CE(sat)	2.5 V at I_C = 3 A, I_B = 6 mA - sets conduction loss (7.5 W at 3 A), directly impacting efficiency in switching regulators.
V_F	4 V at I_F = 8 A - forward drop of integrated antiparallel diode; limits reverse recovery energy in inductive snubber circuits.

Pinout & Package

TO-220 plastic package with vertical mounting orientation, metal tab electrically connected to collector (Pin 2). Standard 3-pin layout: Pin 1 = Base, Pin 2 = Collector (tab), Pin 3 = Emitter.

Pin/Terminal	Circuit Role	Design Meaning
Pin 1	Base	Control input; accepts low-current drive (≤ 0.25 A); internal R1/R2 network simplifies biasing.
Pin 2	Collector (Tab)	Main power output node; electrically tied to metal tab - must be insulated from chassis unless common-collector topology is used.
Pin 3	Emitter	Power return path; carries full load current; referenced to system ground in low-side switch configurations.

Key Features

Feature	Design Value
Monolithic Darlington structure	Integrates driver + output transistor on one die, eliminating interconnect parasitics and improving reliability vs. discrete pairs.
Built-in base-emitter resistors	R1 ≈ 10 kΩ and R2 ≈ 150 Ω enable direct logic-level drive without external bias components.
150 °C max junction temperature	Supports operation in sealed enclosures or high-ambient industrial environments without forced air cooling.
Complementary PNP pairing	BDX34C matches BDX33C in voltage/current ratings and SOA, enabling symmetrical push-pull output stages.
TO-220 mechanical standardization	Enables drop-in replacement across legacy designs using JEDEC-standard heatsinks and mounting hardware.

Applications

Audio Power Amplifier Output Stage

DC Motor Drive (Low-Side Switch)

Use Scenario: Final output stage in 30–60 W Class AB audio amplifiers driving 4–8 Ω speakers.

IC Role / Device Role / Timing Role: NPN Darlington delivers high-current, low-distortion output with minimal base drive overhead.

Use Value: h_FE ≥ 750 ensures <5 mA base current suffices for 3 A peak speaker current, easing driver IC selection.

Use Scenario: Low-side switch controlling brushed DC motors in industrial actuators (24–48 V, up to 8 A).

IC Role / Device Role / Timing Role: Power switching element turning motor current on/off under microcontroller PWM control.

Use Value: Integrated antiparallel diode (V_F = 4 V @ 8 A) clamps inductive kickback without external flyback diode.

Linear Voltage Regulator Pass Element

High-Voltage Relay Driver

Use Scenario: Series pass transistor in adjustable 0–100 V, 3 A linear bench power supplies.

IC Role / Device Role / Timing Role: Dissipative regulation element handling up to 70 W at T_c = 25 °C with proper heatsinking.

Use Value: R_thj-case = 1.78 °C/W allows stable operation at 100 V × 3 A = 300 W input–output differential when heatsinked to ≤ 1.0 °C/W.

Use Scenario: Driving 100 V, 500 mA coil relays in programmable logic controllers (PLCs).

IC Role / Device Role / Timing Role: High-voltage interface between low-power logic and inductive relay load.

Use Value: V_CEO = 100 V exceeds typical relay coil breakdown margins (≥ 150 % of rated voltage), ensuring long-term reliability.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJD127	TO-252 (DPAK), lower P_tot = 30 W, V_CEO = 100 V, h_FE = 1000 min	Suitable only for surface-mount PCBs with limited thermal mass; not interchangeable in through-hole TO-220 footprints.	Select when board space is constrained and power dissipation stays below 25 W with adequate copper pour.
TIP142	TO-220, same package, V_CEO = 100 V, I_C = 10 A, but h_FE = 1000 min and R_thj-case = 1.9 °C/W	Higher gain reduces base drive burden; slightly worse thermal performance requires marginally larger heatsink.	Prefer for new designs needing higher h_FE stability across temperature, accepting minor thermal trade-off.

Compared with MJD127 and TIP142, the BDX33C offers the best balance of proven through-hole robustness, SOA margin at high V_CE, and integrated bias resistors - making it preferred for repair, legacy upgrades, and thermally demanding linear applications.

Availability

BDX33C is available at Aetrix Electronics and suitable for audio amplifier output stages, DC motor drive circuits, linear regulator pass elements, and high-voltage relay drivers requiring stable component supply across extended production lifecycles.

Supply support for BDX33C 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, Switzerland, specializing in power management, analog, microcontrollers, and automotive-grade devices.

The BDX33C belongs to ST's legacy power bipolar transistor family, engineered specifically for industrial linear and switching power stages where ruggedness, SOA integrity, and thermal reliability outweigh digital integration needs.

FAQ

Is the BDX33C pin-compatible with the BDX33B?

Yes - both share identical TO-220 pinout (Base–Collector–Emitter) and mechanical dimensions. The BDX33C differs only in higher voltage ratings (V_CEO = 100 V vs. 80 V) and higher leakage limits (ICEO up to 10 mA at 100 °C), making it a direct upgrade in most designs without layout changes.

Can the BDX33C be used without an external heatsink?

No - even at 1 A collector current, power dissipation exceeds 2.5 W, raising junction temperature beyond safe limits without thermal management. At rated 10 A, 70 W dissipation requires a heatsink with thermal resistance ≤ 1.78 °C/W to hold T_j ≤ 150 °C at 25 °C ambient.

What is the role of the internal 10 kΩ and 150 Ω resistors?

These resistors form a built-in base bias network: the 10 kΩ resistor pulls the base toward emitter to ensure turn-off, while the 150 Ω resistor limits base current during turn-on. Together, they allow direct connection to TTL/CMOS logic outputs without external components, reducing bill-of-materials count and PCB area.

How does the BDX33C compare to modern MOSFET alternatives in switching applications?

The BDX33C has higher V_CE(sat) (2.5 V) than low-R_DS(on) MOSFETs, resulting in greater conduction loss at high current. However, it avoids gate drive complexity, dv/dt-induced false triggering, and body diode reverse recovery issues - making it more robust in noisy industrial environments with inductive loads and no gate driver circuitry.

BDX33C Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

Package/Case:: TO-220-3

Packaging:: Tube

Product Status:: Active

Transistor Type:: NPN - Darlington

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

Voltage - Collector Emitter Breakdown (Max):: 100 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:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-220

BDX33C FAQ

1.How can I place an order for BDX33C through Aetrix?

Please submit a Request for Quotation (RFQ) for BDX33C 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 BDX33C reliable?

The price and inventory of BDX33C are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BDX33C is usually 5 days.

3.What payment methods are accepted for BDX33C?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BDX33C transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BDX33C?

BDX33C orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BDX33C 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 BDX33C?

For technical support, including BDX33C datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BDX33C requirements.

6.How does Aetrix verify that BDX33C is sourced from the original manufacturer or authorized distributors?

All BDX33C 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 BDX33C meets industry standards.

7.What is the process for return or replacement of BDX33C?

All BDX33C units undergo pre-shipment inspection (PSI). If there is an issue with BDX33C, 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 BDX33C part is unused and in its original packaging.

Return procedure for BDX33C:

1.Submit a request within 90 days.

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

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