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

onsemi BCW32

Name: BCW32
Brand: onsemi
SKU: BCW32
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BCW32

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

Package:: TO-236-3, SC-59, SOT-23-3

Datasheet:: BCW32.pdf

Description:: TRANS NPN 32V 0.5A SOT-23-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BCW32 from Fairchild Semiconductor is an NPN general-purpose bipolar junction transistor (BJT) designed for amplification and switching in low-power analog and digital circuits, with V_CEO = 32 V, I_C = 500 mA, h_FE = 200–450 at I_C = 2 mA, V_CE(sat) = 0.25 V at I_C = 10 mA, and f_T = 200 MHz - used in signal conditioning stages of portable audio preamps and LED driver bias networks.

For engineers reviewing the BCW32 datasheet, pinout, applications, or equivalent options, key selection considerations include its SOT-23 package footprint, DC current gain range, saturation voltage under defined drive conditions, thermal resistance (R_θJA = 357 °C/W), and noise figure (NF = 10 dB at 1 kHz).

Technical Context

The BCW32 operates as a discrete NPN BJT with fixed emitter-base and collector-base junction structures optimized for linear amplification and moderate-speed switching. Its h_FE variation across I_C (2–500 mA) and temperature (−40 to +125 °C) is characterized in typical curves, and its f_T = 200 MHz confirms suitability for RF front-end biasing up to ~35 MHz fundamental operation.

Thermal performance is defined for mounting on FR-4 PCB (40 mm × 40 mm × 1.5 mm), with P_D = 350 mW at T_A = 25 °C and derating at 2.8 mW/°C above that. Junction temperature is limited to 150 °C, and storage extends to −55 °C.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	32 V - maximum safe collector-emitter voltage before breakdown; sets upper rail limit in amplifier or switch stage.
I_C (DC)	500 mA - continuous collector current handling; supports medium-current load switching or driver stages.
h_FE	200–450 - DC current gain at I_C = 2 mA, V_CE = 5 V; determines base drive requirement for target collector current.
V_CE(sat)	0.25 V - collector-emitter saturation voltage at I_C = 10 mA, I_B = 0.5 mA; defines conduction loss in switching applications.
f_T	200 MHz - current-gain bandwidth product; indicates usable small-signal amplification up to ~35 MHz with stable gain.
NF	10 dB - noise figure at I_C = 0.2 mA, V_CE = 5 V, R_S = 2 kΩ, 1 kHz, 200 Hz BW; relevant for low-level audio or sensor signal amplification.
R_θJA	357 °C/W - junction-to-ambient thermal resistance on standard FR-4; dictates temperature rise under power dissipation.

Pinout & Package

SOT-23 plastic surface-mount package (3-pin, 1.90 mm × 1.30 mm × 0.95 mm), marked "D2", with standardized lead frame geometry and thermal pad design per Fairchild specification.

Pin/Terminal	Circuit Role	Design Meaning
1 (Base)	Current-controlled input node	Receives base drive current to modulate collector current; requires series resistor for bias stability in linear use.
2 (Emitter)	Common reference terminal	Typically grounded or connected to emitter degeneration resistor; forms return path for base and collector currents.
3 (Collector)	Output current terminal	Delivers amplified/saturated output current; connects to load or next stage; must respect V_CEO and P_D limits.

Key Features

Feature	Design Value
High DC current gain range	h_FE = 200–450 enables low-base-drive designs for battery-powered signal amplifiers.
Low V_CE(sat)	0.25 V at I_C = 10 mA reduces conduction loss and self-heating in switching mode.
Controlled noise performance	NF = 10 dB at 1 kHz supports fidelity-critical preamplifier stages without added filtering.
Standardized SOT-23 footprint	Enables drop-in replacement with other SOT-23 NPN transistors and compatibility with automated assembly.
Wide operating temperature	−55 °C to +150 °C junction range allows deployment in industrial ambient environments.

Applications

Audio Signal Amplification	LED Driver Bias Control
Use Scenario: Low-voltage, low-noise preamplifier stage in portable headphone amplifiers or microphone interfaces. IC Role / Device Role / Timing Role: NPN BJT configured in common-emitter topology to provide voltage and current gain with minimal added noise. Use Value: NF = 10 dB and h_FE ≥ 200 ensure clean signal amplification without requiring multi-stage compensation.	Use Scenario: Constant-current bias network for high-brightness LED strings in automotive interior lighting. IC Role / Device Role / Timing Role: Linear current regulator using emitter-degeneration resistor, driven by microcontroller GPIO. Use Value: V_CEO = 32 V accommodates 24 V system rails with margin; I_C = 500 mA supports multi-LED loads.
Switching Power Supply Feedback	Industrial Sensor Interface
Use Scenario: Optocoupler-driven feedback transistor in isolated 5–12 V DC-DC converters. IC Role / Device Role / Timing Role: Fast-switching NPN switch translating opto-output into PWM controller enable/disable signal. Use Value: f_T = 200 MHz and t_r/t_f < 300 ns support reliable operation at 100–500 kHz switching frequencies.	Use Scenario: Signal conditioning front-end for resistive temperature detectors (RTDs) in PLC analog input modules. IC Role / Device Role / Timing Role: Current-source driver for 2-wire RTD excitation, with gain-stable h_FE over temperature. Use Value: h_FE maintained across −40 to +125 °C ensures consistent excitation current accuracy without recalibration.

Audio Signal Amplification

LED Driver Bias Control

Use Scenario: Low-voltage, low-noise preamplifier stage in portable headphone amplifiers or microphone interfaces.

IC Role / Device Role / Timing Role: NPN BJT configured in common-emitter topology to provide voltage and current gain with minimal added noise.

Use Value: NF = 10 dB and h_FE ≥ 200 ensure clean signal amplification without requiring multi-stage compensation.

Use Scenario: Constant-current bias network for high-brightness LED strings in automotive interior lighting.

IC Role / Device Role / Timing Role: Linear current regulator using emitter-degeneration resistor, driven by microcontroller GPIO.

Use Value: V_CEO = 32 V accommodates 24 V system rails with margin; I_C = 500 mA supports multi-LED loads.

Switching Power Supply Feedback

Industrial Sensor Interface

Use Scenario: Optocoupler-driven feedback transistor in isolated 5–12 V DC-DC converters.

IC Role / Device Role / Timing Role: Fast-switching NPN switch translating opto-output into PWM controller enable/disable signal.

Use Value: f_T = 200 MHz and t_r/t_f < 300 ns support reliable operation at 100–500 kHz switching frequencies.

Use Scenario: Signal conditioning front-end for resistive temperature detectors (RTDs) in PLC analog input modules.

IC Role / Device Role / Timing Role: Current-source driver for 2-wire RTD excitation, with gain-stable h_FE over temperature.

Use Value: h_FE maintained across −40 to +125 °C ensures consistent excitation current accuracy without recalibration.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN general-purpose amplifier applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC846B	h_FE = 200–450 (same range), but V_CEO = 65 V and P_D = 310 mW; slightly lower thermal resistance (R_θJA = 300 °C/W).	Higher voltage rating suits 48 V industrial bus interfaces; lower P_D limits sustained 500 mA operation.	Select BC846B when higher V_CEO margin is required and peak I_C remains ≤ 300 mA.
MMBT3904	h_FE = 100–300 (narrower range), V_CEO = 40 V, P_D = 310 mW, f_T = 300 MHz; identical SOT-23 package and pinout.	Higher f_T benefits RF biasing; lower h_FE may require increased base drive in linear amplifiers.	Select MMBT3904 where bandwidth > 100 MHz is critical and gain tolerance ≥ 100 is acceptable.

Compared with BCW32, BC846B offers higher voltage headroom but reduced power handling, while MMBT3904 delivers greater bandwidth at the cost of lower minimum h_FE; all three share SOT-23 packaging but differ in gain consistency, thermal limits, and frequency response trade-offs.

Availability

BCW32 is available at Aetrix Electronics and suitable for audio signal amplification, LED driver bias control, and switching power supply feedback requiring stable component supply and long-term industrial availability.

Supply support for BCW32 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

Fairchild Semiconductor was a U.S.-based semiconductor manufacturer specializing in power management, analog, and discrete devices before its acquisition by ON Semiconductor in 2016.

The BCW32 belongs to Fairchild's legacy general-purpose BJT family, engineered for cost-sensitive, medium-frequency amplification and switching in consumer, industrial, and automotive auxiliary systems.

FAQ

What is the maximum continuous collector current for BCW32?

The BCW32 supports a maximum DC collector current (I_C) of 500 mA at T_A = 25 °C, as specified in its Absolute Maximum Ratings table. Operation at this current requires adherence to thermal derating (2.8 mW/°C above 25 °C) and verification of junction temperature stay below 150 °C. The BCW32 datasheet confirms this rating applies under standard FR-4 PCB mounting conditions.

Does BCW32 have a documented pinout for SOT-23 package?

Yes, the BCW32 uses standard SOT-23 pin configuration: Pin 1 = Base, Pin 2 = Emitter, Pin 3 = Collector - confirmed in the device marking diagram and package outline drawing in the Fairchild BCW32 datasheet Rev. A. The top-mark "D2" aligns with this orientation, and no alternate pinouts are documented for this part number.

What is the typical noise figure of BCW32 and under what conditions?

The BCW32 has a typical noise figure (NF) of 10 dB, measured at I_C = 0.2 mA, V_CE = 5.0 V, source resistance R_S = 2.0 kΩ, frequency f = 1.0 kHz, and bandwidth BW = 200 Hz. This value is specified in the Electrical Characteristics table and reflects its suitability for low-noise preamplifier applications where signal integrity is critical.

Can BCW32 be used in switching applications, and what supports that capability?

Yes, BCW32 is qualified for switching use, supported by V_CE(sat) = 0.25 V at I_C = 10 mA / I_B = 0.5 mA, rise/fall times < 300 ns (per Figure 7), and f_T = 200 MHz. These parameters confirm fast turn-on/turn-off behavior and low conduction loss - enabling reliable operation in PWM-driven LED drivers and DC-DC converter feedback paths.

What is the thermal resistance junction-to-ambient for BCW32?

The BCW32 has a thermal resistance R_θJA of 357 °C/W when mounted on a standard FR-4 PCB (40 mm × 40 mm × 1.5 mm). This value is measured under specified board layout conditions and directly impacts allowable power dissipation - for example, at T_A = 70 °C, maximum safe P_D drops to approximately 150 mW to maintain T_J ≤ 150 °C.

BCW32 Specifications

Product attributes: Attribute value

Manufacturer:: onsemi

Series:: -

Package/Case:: TO-236-3, SC-59, SOT-23-3

Packaging:: Tape & Reel (TR)

Product Status:: Obsolete

Transistor Type:: NPN

Current - Collector (Ic) (Max):: 500 mA

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

Vce Saturation (Max) @ Ib, Ic:: 250mV @ 500µA, 10mA

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

DC Current Gain (hFE) (Min) @ Ic, Vce:: 200 @ 2mA, 5V

Power - Max:: 350 mW

Frequency - Transition:: 200MHz

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

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-3

BCW32 FAQ

1.How can I place an order for BCW32 through Aetrix?

Please submit a Request for Quotation (RFQ) for BCW32 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 BCW32 reliable?

The price and inventory of BCW32 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BCW32 is usually 5 days.

3.What payment methods are accepted for BCW32?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BCW32 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BCW32?

BCW32 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BCW32 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 BCW32?

For technical support, including BCW32 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BCW32 requirements.

6.How does Aetrix verify that BCW32 is sourced from the original manufacturer or authorized distributors?

All BCW32 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 BCW32 meets industry standards.

7.What is the process for return or replacement of BCW32?

All BCW32 units undergo pre-shipment inspection (PSI). If there is an issue with BCW32, 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 BCW32 part is unused and in its original packaging.

Return procedure for BCW32:

1.Submit a request within 90 days.

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

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