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

onsemi BD435

Name: BD435
Brand: onsemi
SKU: BD435
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BD435

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-225AA, TO-126-3

Datasheet:: BD435.pdf

Description:: TRANS NPN 32V 4A TO-126

Quantity:: RFQ Add To RFQ list

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Inventory:4,172

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Product details

Overview

BD435 from STMicroelectronics is a silicon epitaxial-base NPN power transistor in JEDEC SOT-32 (TO-126) package, rated for 32 V V_CEO, 4 A I_C, and 36 W P_tot at T_c ≤ 25 °C, designed for medium-power linear amplification and switching in automotive audio output stages and industrial power control circuits.

For engineers reviewing the BD435 datasheet, BD435 pinout, BD435 application, or BD435 equivalent, key selection criteria include its 32 V collector-emitter sustaining voltage, 0.5 V V_CE(sat) at 2 A/0.2 A drive, DC current gain of 40–130 across operating conditions, thermal resistance of 3.5 °C/W junction-to-case, and compatibility with complementary PNP BD436 in push-pull configurations.

Technical Context

The BD435 operates as a medium-power bipolar junction transistor with epitaxial base construction, supporting both linear-mode amplification (e.g., Class AB audio output) and hard-switching applications up to 32 V and 4 A continuous collector current. Its V_CEO(sus) = 32 V and V_CE(sat) = 0.5 V at I_C = 2 A / I_B = 0.2 A define its safe operating area under pulsed and DC conditions.

Thermal design relies on direct case mounting to heatsinks, enabled by low R_thj-case = 3.5 °C/W; ambient operation is limited by R_thj-amb = 100 °C/W. The device features matched h_FE pairs (h_FE1/h_FE2 ≤ 1.4) and f_T = 3 MHz, supporting audio-frequency switching and analog signal amplification without high-frequency compensation.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	32 V - Maximum collector-emitter voltage with base open; defines safe linear/saturation boundary in switching designs
I_C	4 A - Continuous collector current rating; sets maximum load-handling capability in power stages
P_tot	36 W - Total power dissipation at case temperature ≤ 25 °C; requires heatsink for sustained operation
V_CE(sat)	0.5 V @ 2 A / 0.2 A - Low saturation voltage reduces conduction loss in switching applications
h_FE	40–130 - DC current gain range across I_C = 10 mA to 2 A; enables stable biasing in linear and switching modes
R_thj-case	3.5 °C/W - Junction-to-case thermal resistance; determines minimum heatsink requirement for thermal management
f_T	3 MHz - Transition frequency; supports audio-band amplification and PWM switching up to ~300 kHz

Pinout & Package

BD435 uses the JEDEC-standard SOT-32 (equivalent to TO-126) plastic package with metal tab for heatsinking. Pin 1 is Base, Pin 2 is Collector (connected to tab), Pin 3 is Emitter.

Pin/Terminal	Circuit Role	Design Meaning
1 (Base)	Control input	Receives base current to drive transistor into active/saturation; requires current-limiting resistor in most driver circuits
2 (Collector)	Power output node	Connected internally to metal tab; must be electrically isolated from heatsink unless circuit ground reference permits
3 (Emitter)	Current return path	Serves as common emitter node in grounded-emitter configuration; often tied to system ground or low-side switch reference

Key Features

Feature	Design Value
Complementary pairing	Matched with BD436 (PNP) for push-pull amplifier stages; h_FE ratio ≤ 1.4 ensures balanced conduction
High ruggedness	V_CEO(sus) = 32 V with I_C = 100 mA pulse; sustains transient overvoltage in automotive 12 V systems
Low saturation loss	V_CE(sat) = 0.5 V at 2 A enables <1 W conduction loss per device in Class AB output stages
Thermal robustness	Junction temperature rated to 150 °C; R_thj-case = 3.5 °C/W allows compact heatsink integration in space-constrained enclosures
Audio-grade linearity	h_FE variation ≤ ±20% across I_C = 10 mA–2 A ensures consistent gain in linear amplifiers without dynamic compensation

Applications

Automotive Audio Output Stage

Industrial DC Motor Driver

Use Scenario: Medium-power speaker driver in car radio head units requiring reliable 12 V supply operation and thermal resilience.

IC Role / Device Role / Timing Role: NPN power switch in complementary Class AB output stage, delivering up to 15 W RMS into 4 Ω loads.

Use Value: 32 V V_CEO accommodates battery transients; 0.5 V V_CE(sat) minimizes heat generation during peak output.

Use Scenario: H-bridge low-side switch controlling brushed DC motors in factory automation equipment.

IC Role / Device Role / Timing Role: High-current NPN switch enabling bidirectional motor control when paired with BD436 in totem-pole configuration.

Use Value: 4 A I_C rating supports motors drawing up to 3 A continuous; 3.5 °C/W R_thj-case enables forced-air–cooled PCB mounting.

Linear Voltage Regulator Pass Element

Switch-Mode Power Supply Switch

Use Scenario: Series pass transistor in adjustable 0–30 V, 2 A bench power supply with foldback current limiting.

IC Role / Device Role / Timing Role: Linear regulator pass element dissipating up to 30 W under worst-case dropout conditions.

Use Value: 36 W P_tot and 150 °C T_j(max) allow safe operation with moderate heatsinking; low V_CE(sat) improves regulation efficiency.

Use Scenario: Primary-side switching transistor in 50–100 kHz flyback converter for industrial auxiliary power supplies.

IC Role / Device Role / Timing Role: Hard-switched NPN power transistor driven by discrete gate driver, handling repetitive 32 V, 2 A pulses.

Use Value: 3 MHz f_T ensures adequate gain margin at switching frequencies; V_CEO(sus) = 32 V provides margin against reflected voltage spikes.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BD437	Higher V_CEO = 45 V, same package and pinout; h_FE min 30 at I_C = 2 A	Supports higher bus voltages (e.g., 24 V industrial systems); slightly lower gain at high current	Select when >32 V rail stability or transient margin is required; otherwise BD435 offers better cost/performance balance at 12 V
TIP31C	Same V_CEO = 100 V (TO-220), higher I_C = 3 A, but larger footprint and R_thj-case = 5 °C/W	Requires larger PCB area and heavier heatsinking; not drop-in compatible due to package and pinout mismatch	Choose only if TO-220 mechanical fit is mandated or higher voltage headroom (>45 V) is needed; SOT-32 footprint advantage favors BD435 in space-limited designs

Compared with BD437 and TIP31C, BD435 delivers optimal thermal performance (3.5 °C/W) and gain consistency in 12 V automotive and industrial linear applications, while avoiding unnecessary voltage overhead or board-space penalty.

Availability

BD435 is available at Aetrix Electronics and suitable for automotive audio output stages, industrial DC motor drivers, linear voltage regulator pass elements, and switch-mode power supply switches requiring stable component supply and long-term manufacturability.

Supply support for BD435 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 components.

The BD435 belongs to ST's legacy silicon power transistor family, engineered specifically for cost-sensitive, thermally demanding linear and switching applications in automotive and industrial environments where reliability under sustained thermal stress is critical.

FAQ

Is BD435 RoHS compliant?

Yes, BD435 is RoHS compliant per STMicroelectronics' product change notification PCN 09-0012, effective June 2009. All BD43x series devices manufactured after that date meet EU Directive 2011/65/EU requirements, including lead-free terminations and halogen-free molding compounds.

Can BD435 be used in parallel configurations?

Yes, BD435 supports parallel operation with current-sharing resistors (0.1–0.22 Ω emitter degeneration) due to its positive temperature coefficient of V_CE(sat). Matching h_FE within ±15% and identical thermal mounting are required to ensure balanced current distribution across multiple devices.

What is the maximum safe operating area (SOA) limit at 100 °C case temperature?

At T_c = 100 °C, BD435's SOA is limited to 1.8 A at 32 V (DC), 2.5 A at 15 V, or 4 A at 5 V, based on derated P_tot = 18 W and thermal runaway constraints. Pulse operation (≤10 ms, 1.5% duty) extends limits to 7 A peak at 32 V.

Does BD435 require a base-emitter resistor for stability?

Yes, a 10–100 kΩ base-emitter resistor (R_BE) is recommended to prevent leakage-induced turn-on during high-temperature operation or when driving inductive loads. This resistor ensures reliable cutoff by shunting ICBO (≤100 µA) and maintaining V_BE < 0.5 V under off-state conditions.

BD435 Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-225AA, TO-126-3

Packaging:: Bulk

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 4 A

Voltage - Collector Emitter Breakdown (Max):: 32 V

Vce Saturation (Max) @ Ib, Ic:: 500mV @ 200mA, 2A

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

DC Current Gain (hFE) (Min) @ Ic, Vce:: 85 @ 500mA, 1V

Power - Max:: 36 W

Frequency - Transition:: 3MHz

Operating Temperature:: -55°C ~ 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: TO-126

BD435 FAQ

1.How can I place an order for BD435 through Aetrix?

Please submit a Request for Quotation (RFQ) for BD435 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 BD435 reliable?

The price and inventory of BD435 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BD435 is usually 5 days.

3.What payment methods are accepted for BD435?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BD435 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BD435?

BD435 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BD435 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 BD435?

For technical support, including BD435 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BD435 requirements.

6.How does Aetrix verify that BD435 is sourced from the original manufacturer or authorized distributors?

All BD435 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 BD435 meets industry standards.

7.What is the process for return or replacement of BD435?

All BD435 units undergo pre-shipment inspection (PSI). If there is an issue with BD435, 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 BD435 part is unused and in its original packaging.

Return procedure for BD435:

1.Submit a request within 90 days.

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

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