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

STMicroelectronics BD434

Name: BD434
Brand: STMicroelectronics
SKU: BD434
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BD434

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

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

Datasheet:: BD434.pdf

Description:: TRANS PNP 22V 4A SOT-32-3

Quantity:: RFQ Add To RFQ list

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Inventory:7,796

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Product details

Overview

BD434 from STMicroelectronics is a complementary PNP silicon epitaxial-base power transistor in SOT-32 (TO-126) package, rated for V_CEO = –22 V, I_C = –4 A, and P_tot = 36 W at T_c ≤ 25 °C; designed for medium-power linear and switching applications including car-radio output stages.

For engineers reviewing the BD434 datasheet, BD434 pinout, BD434 application, or BD434 equivalent, key selection factors include its negative voltage/current ratings, DC current gain (h_FE = 40–130), saturation voltage (V_CE(sat) = –0.2 to –0.5 V), thermal resistance (R_thj-case = 3.5 °C/W), and SOT-32 mechanical compatibility with BD433/BD435 pairs.

Technical Context

The BD434 operates as a medium-power PNP bipolar junction transistor with epitaxial base construction, supporting both linear amplification and hard-switching modes. Its absolute maximum ratings are fully symmetrical and complementary to the NPN BD433, enabling push-pull stage design without topology rework.

Electrical behavior is defined under case temperature control (T_c = 25 °C), with pulsed test conditions (300 µs, 1.5% duty cycle) applied to V_CEO(sus), V_CE(sat), and V_BE measurements. Thermal performance relies on direct heatsink mounting via the collector tab (Pin 2), leveraging low R_thj-case = 3.5 °C/W.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	–22 V: Maximum safe collector-emitter voltage with base open; defines upper limit for rail-to-rail swing in Class AB audio output stages.
I_C	–4 A: Continuous DC collector current; supports ≥15 W linear output into 4 Ω loads with adequate heatsinking.
P_tot	36 W at T_c ≤ 25 °C: Total dissipation capability when mounted on heatsink; requires thermal interface design per R_thj-case = 3.5 °C/W.
h_FE	40–130 @ I_C = 10 mA–2 A: Wide DC current gain range enables stable biasing across operating points in driver and output stages.
V_CE(sat)	–0.2 to –0.5 V @ I_C = –2 A, I_B = –0.2 A: Low saturation voltage minimizes conduction loss and self-heating in switching applications.
f_T	3 MHz @ I_C = –250 mA: Transition frequency supports audio-frequency amplification up to ~100 kHz with usable gain margin.

Pinout & Package

SOT-32 (TO-126) package with isolated metal tab (collector) for direct heatsink mounting; plastic body with three leads in inline configuration. Pin 1 = Base, Pin 2 = Collector (tab), Pin 3 = Emitter.

Pin/Terminal	Circuit Role	Design Meaning
1 (Base)	Control input	Current-driven gate requiring external base resistor network for proper turn-on/turn-off timing and saturation control.
2 (Collector)	Power output node	Electrically connected to metal tab; must be insulated from heatsink unless circuit ground reference permits direct thermal path.
3 (Emitter)	Reference terminal	Common return path for load current; polarity reversal vs. NPN devices requires complementary bias network layout.

Key Features

Feature	Design Value
Complementary pairing	Matched electrical specs and mechanical footprint with BD433 (NPN), enabling symmetric push-pull amplifier designs without layout redesign.
High ruggedness	Rated for V_CEO(sus) = –22 V at I_C = –100 mA, supporting reliable operation under inductive load switching transients.
Low thermal resistance	R_thj-case = 3.5 °C/W enables compact heatsink solutions for 15–20 W continuous output in automotive audio systems.
Epitaxial base construction	Improves high-current gain linearity and reduces second breakdown risk compared to diffused-base alternatives.

Applications

Car Radio Output Stage

DC Motor Driver Half-Bridge

Use Scenario: Medium-power audio output stage in OEM automotive head units driving 4 Ω speakers.

IC Role / Device Role / Timing Role: PNP output transistor in complementary Class AB push-pull pair with BD433.

Use Value: Delivers low-distortion 15 W output with V_CE(sat) ≤ –0.5 V and h_FE ≥ 40 at full load, minimizing thermal derating.

Use Scenario: High-side switch in brushed DC motor control for HVAC actuators or seat adjusters.

IC Role / Device Role / Timing Role: PNP power switch controlling motor supply rail in conjunction with NPN low-side driver.

Use Value: Supports 4 A continuous motor current with robust V_CEO = –22 V rating, tolerating back-EMF spikes up to 18 V.

Linear Voltage Regulator Pass Element

Switch-Mode Power Supply Driver

Use Scenario: Series pass transistor in 12 V automotive LDO regulators supplying infotainment subsystems.

IC Role / Device Role / Timing Role: PNP-controlled current source regulating output voltage via emitter-follower configuration.

Use Value: Stable h_FE over temperature ensures predictable dropout and load regulation; R_thj-case allows integration into compact PCB-mounted heatsinks.

Use Scenario: Gate driver stage for external MOSFETs in 24 V industrial SMPS auxiliary supplies.

IC Role / Device Role / Timing Role: Fast-switching PNP transistor amplifying PWM signals to drive high-capacitance MOSFET gates.

Use Value: f_T = 3 MHz and low V_CE(sat) enable clean 100 kHz switching with <100 ns rise/fall times under 1 nF load.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
MJD44H11	V_CEO = –80 V, I_C = –8 A, P_tot = 50 W, TO-252 package	Higher voltage/current rating; surface-mount instead of through-hole	Select when higher breakdown margin or SMT assembly is required; requires PCB layout change and thermal pad redesign.
BD440	V_CEO = –40 V, I_C = –4 A, P_tot = 36 W, same SOT-32 package	Higher voltage rating but lower h_FE (min 25) and higher V_CE(sat) (–0.7 V)	Select for 24 V systems needing extra V_CEO margin; accept reduced gain and higher conduction loss.

Compared with MJD44H11 and BD440, BD434 offers optimal balance of voltage rating, gain, saturation performance, and legacy SOT-32 compatibility for 12 V automotive linear and switching applications where pin-for-pin BD433 pairing is essential.

Availability

BD434 is available at Aetrix Electronics and suitable for car-radio output stages, DC motor drivers, linear voltage regulators, and SMPS gate drivers requiring stable component supply and long-term obsolescence management.

Supply support for BD434 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 analog, digital, and mixed-signal ICs and discrete components for automotive, industrial, and consumer markets.

The BD series power transistors were developed specifically for cost-sensitive, medium-power linear and switching applications in automotive audio and industrial controls, emphasizing ruggedness, thermal efficiency, and complementary pairing.

FAQ

Is BD434 pin-compatible with BD433?

Yes - BD434 uses identical SOT-32 (TO-126) packaging and pinout (Base–Collector–Emitter) as BD433, enabling direct placement in complementary push-pull circuits. Polarity reversal is handled entirely by schematic symbol orientation and bias network polarity, not physical layout.

What is the maximum safe operating temperature for BD434?

The BD434 has a maximum junction temperature (T_j) of 150 °C and storage temperature range of –65 to +150 °C. To sustain continuous 4 A operation, case temperature must remain ≤25 °C - requiring heatsink design that maintains R_thj-amb ≤ 97 °C/W with ambient ≤70 °C.

Can BD434 replace BD436 or BD438 in a circuit?

No - BD434 is rated for V_CEO = –22 V, while BD436 and BD438 are rated for –32 V and –45 V respectively. Substituting BD434 in circuits designed for higher-voltage PNP devices risks premature breakdown under transient overvoltage or inductive kickback conditions.

Does BD434 require a base resistor in switching applications?

Yes - BD434 is a current-controlled device requiring externally calculated base resistor(s) to ensure sufficient I_B for saturation (e.g., ≥0.2 A for 2 A I_C). Omitting or undersizing the base resistor causes incomplete turn-on, excessive V_CE, and thermal runaway under load.

BD434 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

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

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: PNP

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

Voltage - Collector Emitter Breakdown (Max):: 22 V

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

Current - Collector Cutoff (Max):: 100µA

DC Current Gain (hFE) (Min) @ Ic, Vce:: 40 @ 10mA, 5V

Power - Max:: 36 W

Frequency - Transition:: 3MHz

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: SOT-32-3

BD434 FAQ

1.How can I place an order for BD434 through Aetrix?

Please submit a Request for Quotation (RFQ) for BD434 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 BD434 reliable?

The price and inventory of BD434 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BD434 is usually 5 days.

3.What payment methods are accepted for BD434?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BD434 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BD434?

BD434 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BD434 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 BD434?

For technical support, including BD434 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BD434 requirements.

6.How does Aetrix verify that BD434 is sourced from the original manufacturer or authorized distributors?

All BD434 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 BD434 meets industry standards.

7.What is the process for return or replacement of BD434?

All BD434 units undergo pre-shipment inspection (PSI). If there is an issue with BD434, 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 BD434 part is unused and in its original packaging.

Return procedure for BD434:

1.Submit a request within 90 days.

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

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