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

STMicroelectronics BD235

Name: BD235
Brand: STMicroelectronics
SKU: BD235
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BD235

Manufacturer:: STMicroelectronics

Category:: Single Bipolar Transistors

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

Datasheet:: BD235.pdf

Description:: TRANS NPN 60V 2A SOT-32-3

Quantity:: RFQ Add To RFQ list

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Inventory:3,196

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Product details

Overview

BD235 from STMicroelectronics is a low-voltage NPN power transistor in SOT-32 (TO-126) package, designed for linear and switching power amplification with V_CEO = 60 V, I_C = 2 A, P_TOT = 25 W at T_case = 25°C, and V_CE(sat) ≤ 0.6 V at I_C = 1 A / I_B = 0.1 A - used in audio output stages and DC-DC converter switches.

For engineers reviewing the BD235 datasheet, BD235 pinout, BD235 application, or BD235 equivalent, key selection criteria include saturation voltage performance under 1 A load, safe operating area at elevated case temperature, h_FE stability across 150 mA–1 A collector current, and compatibility with TO-126 heatsink mounting in industrial power modules.

Technical Context

The BD235 employs Planar technology with "Base Island" layout to achieve high DC current gain (h_FE ≥ 40 at I_C = 150 mA, V_CE = 2 V) while maintaining low V_CE(sat) (≤ 0.6 V). Its V_CER = 60 V rating supports operation with base-emitter resistor bias networks up to 1 kΩ.

Designed for linear-mode operation, it features a maximum junction temperature of 150°C and thermal derating above 25°C case temperature - enabling use in Class AB audio amplifiers and regulated power supply pass elements where thermal stability and low distortion are critical.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	60 V - Maximum collector-emitter voltage with open base; defines safe linear operating ceiling in amplifier and regulator topologies.
I_C	2 A continuous - Rated collector current at T_case = 25°C; sets baseline conduction capability for medium-power switching.
P_TOT	25 W at T_case = 25°C - Total power dissipation limit; requires heatsinking for sustained >5 W operation.
V_CE(sat)	≤ 0.6 V at I_C = 1 A, I_B = 0.1 A - Low saturation loss enables efficient switching in relay drivers and PWM output stages.
h_FE	≥ 40 at I_C = 150 mA, V_CE = 2 V - High DC gain reduces required base drive current in discrete amplifier designs.
V_CB0	60 V - Collector-base breakdown voltage with emitter open; constrains maximum reverse-biased collector swing in inductive load switching.

Pinout & Package

SOT-32 (TO-126) package: three-terminal through-hole plastic power package with integral metal tab for heatsink attachment; pin 1 = emitter, pin 2 = base, pin 3 = collector (tab-connected).

Pin/Terminal	Circuit Role	Design Meaning
1 (Emitter)	Current exit path	Low-impedance terminal tied to ground or negative rail in common-emitter configurations; electrically isolated from metal tab.
2 (Base)	Control input	Receives forward bias current to modulate collector current; requires current-limiting resistor in fixed-bias applications.
3 (Collector)	Current entry path	Connected internally to metal tab; must be electrically insulated from heatsink unless circuit design permits common-collector grounding.

Key Features

Feature	Design Value
Low V_CE(sat)	≤ 0.6 V at 1 A ensures <1.2 W conduction loss in switching mode, reducing thermal burden in compact enclosures.
High h_FE	≥ 40 at 150 mA enables single-stage amplification without Darlington pairing in low-noise preamp outputs.
Planar "Base Island" structure	Improves gain uniformity and reduces leakage (I_CBO ≤ 0.1 mA at 25°C), supporting stable bias in temperature-varying environments.
TO-126 mechanical form	Standardized footprint allows direct replacement in legacy audio amplifier PCBs and industrial control boards using through-hole assembly.

Applications

Audio Power Amplifier

DC-DC Converter Switch

Use Scenario: Final output stage in 10–20 W Class AB audio amplifiers driving 4–8 Ω speakers.

IC Role / Device Role / Timing Role: NPN power switch amplifying line-level signal into speaker current; operates in linear region with symmetrical push-pull pairing.

Use Value: Low V_CE(sat) minimizes crossover distortion and heat generation during mid-level output, improving thermal reliability over extended play.

Use Scenario: Main switching transistor in non-isolated buck converters delivering 5–12 V at up to 1.5 A.

IC Role / Device Role / Timing Role: Medium-speed power switch turning on/off inductor current; driven by PWM controller with ~100 ns–1 µs rise/fall times.

Use Value: High h_FE reduces gate-driver complexity and base drive power, enabling simple transistor-based control in cost-sensitive SMPS designs.

Linear Voltage Regulator

Relay Driver Circuit

Use Scenario: Pass element in adjustable 3–15 V, 1.5 A linear regulators with external feedback network.

IC Role / Device Role / Timing Role: Series-pass transistor regulating output voltage via base-emitter voltage control; dissipates excess input-output differential.

Use Value: 25 W P_TOT rating supports 5 V dropout at 1.5 A with moderate heatsinking, avoiding thermal shutdown in constant-load applications.

Use Scenario: Driving 12 V/500 mA electromagnetic relays in PLC I/O modules and HVAC controllers.

IC Role / Device Role / Timing Role: Saturated switch providing full coil current; base biased via microcontroller GPIO with series resistor.

Use Value: V_CE(sat) ≤ 0.6 V limits relay coil voltage drop to <0.6 V, ensuring reliable pull-in even with 11.4 V minimum supply.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BD237	V_CEO = 80 V, V_CER = 100 V, same package and pinout	Higher voltage headroom for 24 V industrial supplies and flyback snubbers	Select when operating V_CC > 60 V or requiring enhanced avalanche margin in inductive switching.
TIP31C	V_CEO = 100 V, I_C = 3 A, TO-220 package, h_FE min = 10	Larger package, lower gain, higher saturation voltage (V_CE(sat) ≤ 1.2 V)	Choose only if TO-220 mechanical fit is mandatory and lower gain/higher loss are acceptable.

Compared with BD237, the BD235 trades voltage headroom for tighter V_CE(sat) and higher h_FE; versus TIP31C, it delivers superior gain and lower conduction loss in TO-126 space-constrained layouts, but lacks its 100 V rating.

Availability

BD235 is available at Aetrix Electronics and suitable for audio power amplifiers, DC-DC converter switches, and linear voltage regulators requiring stable component supply with consistent parametric performance across production lots.

Supply support for BD235 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 power devices for industrial, automotive, and consumer markets.

The BD235 belongs to ST's legacy bipolar power transistor family, engineered specifically for cost-effective, thermally robust linear and switching power applications in non-automotive industrial equipment.

FAQ

Is BD235 RoHS-compliant and lead-free?

Yes, BD235 is manufactured in ECOPACK®-compliant versions per STMicroelectronics' environmental program. The device meets RoHS Directive 2011/65/EU requirements, with lead-free terminations and halogen-free molding compound - verified in ST's official product change notices and packaging data sheets.

What is the maximum safe operating case temperature for continuous BD235 operation?

The BD235 is rated for continuous operation up to T_case = 25°C at full 25 W dissipation. Above this, power must be linearly derated: 0.2 W/°C reduction beyond 25°C, reaching zero dissipation at 150°C - matching its 150°C maximum junction temperature rating.

Can BD235 replace BD237 in existing designs?

BD235 can replace BD237 only if the application's maximum V_CE does not exceed 60 V. Since BD237 supports 80 V V_CEO, substituting BD235 in 72 V nominal systems risks breakdown. Verify peak collector voltage under all load and transient conditions before substitution.

Does BD235 require a heatsink in 1 A switching applications?

Yes - even at 1 A with 0.6 V V_CE(sat), conduction loss is 0.6 W, and switching losses add further thermal load. Without heatsinking, junction temperature rises rapidly above ambient. A minimum 5 cm² aluminum heatsink is recommended for sustained 1 A pulsed or continuous operation.

BD235 Specifications

Product attributes: Attribute value

Manufacturer:: STMicroelectronics

Series:: -

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

Packaging:: Tube

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 2 A

Voltage - Collector Emitter Breakdown (Max):: 60 V

Vce Saturation (Max) @ Ib, Ic:: 600mV @ 100mA, 1A

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

DC Current Gain (hFE) (Min) @ Ic, Vce:: 25 @ 1A, 2V

Power - Max:: 25 W

Frequency - Transition:: -

Operating Temperature:: 150°C (TJ)

Grade:: -

Qualification:: -

Mounting Type:: Through Hole

Supplier Device Package:: SOT-32-3

BD235 FAQ

1.How can I place an order for BD235 through Aetrix?

Please submit a Request for Quotation (RFQ) for BD235 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 BD235 reliable?

The price and inventory of BD235 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BD235 is usually 5 days.

3.What payment methods are accepted for BD235?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BD235 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BD235?

BD235 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BD235 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 BD235?

For technical support, including BD235 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BD235 requirements.

6.How does Aetrix verify that BD235 is sourced from the original manufacturer or authorized distributors?

All BD235 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 BD235 meets industry standards.

7.What is the process for return or replacement of BD235?

All BD235 units undergo pre-shipment inspection (PSI). If there is an issue with BD235, 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 BD235 part is unused and in its original packaging.

Return procedure for BD235:

1.Submit a request within 90 days.

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

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