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

onsemi BCW33LT1

Name: BCW33LT1
Brand: onsemi
SKU: BCW33LT1
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BCW33LT1

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BCW33LT1.pdf

Description:: TRANS NPN 32V 0.1A SOT23-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BCW33LT1 from onsemi is an NPN silicon general-purpose transistor in SOT-23 package, rated for 32 V_CEO, 100 mA continuous collector current, and DC current gain (h_FE) of 420–800 at I_C = 2 mA. It delivers low V_CE(sat) ≤ 0.25 V at I_C/I_B = 20, supports noise-sensitive small-signal amplification, and is widely used in portable audio preamps and LED driver switching stages.

For engineers reviewing the BCW33LT1 datasheet, pinout, applications, or equivalent options, key selection criteria include verified h_FE range at low bias, thermal resistance (R_JA = 556 °C/W on FR-5), ESD-safe handling per JESD22-A114, Pb-free SOT-23 footprint compatibility, and validated noise figure ≤10 dB at 1 kHz with 2 kΩ source resistance.

Technical Context

The BCW33LT1 is a planar epitaxial NPN transistor optimized for linear amplification and low-power switching. Its structure enables stable h_FE across −55°C to +150°C junction temperature, low C_obo ≤ 4.0 pF at 10 V, and predictable V_BE(on) = 0.55–0.70 V at I_C = 2 mA.

It operates with fixed-base drive configurations and supports Class-A amplifier topologies requiring <10 dB noise figure and sub-0.3 V saturation voltage. Thermal design must account for 225 mW dissipation derating (1.8 mW/°C) on standard FR-5 PCBs.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	32 V - Maximum safe collector-emitter voltage before breakdown under open-base conditions.
I_C (continuous)	100 mA - Continuous collector current limit defining usable linear/saturation range in bias networks.
h_FE	420–800 - DC current gain at I_C = 2 mA, V_CE = 5 V; determines base resistor sizing for stable biasing.
V_CE(sat)	≤ 0.25 V - Saturation voltage at I_C = 10 mA, I_B = 0.5 mA; defines conduction loss in switching applications.
NF	≤ 10 dB - Noise figure at V_CE = 5 V, I_C = 0.2 mA, R_S = 2 kΩ, 1 kHz; critical for low-noise preamplifier stages.
R_JA (FR-5)	556 °C/W - Junction-to-ambient thermal resistance on standard 1.0 × 0.75 inch FR-5 board; governs heatsinking requirements.
C_obo	≤ 4.0 pF - Output capacitance at V_CB = 10 V; limits high-frequency bandwidth in RF-coupled stages.

Pinout & Package

SOT-23 (TO-236AB) plastic surface-mount package, 3-pin, 1.0 mm × 1.4 mm footprint, 0.95 mm height, lead-free compliant (BCW33LT1G variant available).

Pin/Terminal	Circuit Role	Design Meaning
1	Base	Control terminal for forward-biased junction; requires current-limited drive to achieve target h_FE-based collector current.
2	Emitter	Current return path; tied to ground or low-impedance node in common-emitter configurations.
3	Collector	Output current terminal; connects to load or next stage; withstands up to 32 V when base is open.

Key Features

Feature	Design Value
Low saturation voltage	V_CE(sat) ≤ 0.25 V enables efficient switching in battery-powered LED drivers without excessive power loss.
High DC current gain	h_FE = 420–800 allows minimal base drive current, reducing loading on preceding logic or op-amp stages.
Low noise performance	NF ≤ 10 dB at 1 kHz supports use in microphone preamplifiers and sensor signal conditioning where SNR is critical.
Pb-free SOT-23 packaging	RoHS-compliant construction ensures compatibility with modern reflow profiles and environmental compliance requirements.
Wide operating temperature	Junction range −55°C to +150°C supports deployment in automotive cabin modules and industrial control enclosures.

Applications

Portable Audio Preamp	LED Driver Switch
Use Scenario: Amplifying weak signals from electret microphones in Bluetooth headsets and voice recorders. IC Role / Device Role / Timing Role: NPN small-signal amplifier in common-emitter configuration with emitter degeneration for linearity. Use Value: Low 10 dB noise figure and stable h_FE ensure clean gain without introducing audible hiss or distortion at 0.2–2 mA bias points.	Use Scenario: Driving indicator LEDs and status lights in handheld medical devices and IoT sensors. IC Role / Device Role / Timing Role: Low-side switch controlled by MCU GPIO, turning on/off LED strings with 10–30 mA load current. Use Value: V_CE(sat) ≤ 0.25 V minimizes voltage drop and self-heating, preserving battery life and enabling direct 3.3 V MCU interface without level-shifting.
Signal Level Shifter	Current Mirror Reference
Use Scenario: Translating logic levels between 1.8 V and 3.3 V domains in mixed-voltage sensor interfaces. IC Role / Device Role / Timing Role: Active pull-up/pull-down element in open-collector translator circuits with resistive biasing. Use Value: Tight V_BE(on) = 0.55–0.70 V ensures predictable turn-on threshold and fast edge response for sub-10 ns rise/fall times.	Use Scenario: Building matched current sources in analog front-ends for precision ADC biasing and sensor excitation. IC Role / Device Role / Timing Role: One leg of a discrete two-transistor current mirror, leveraging matched h_FE and thermal tracking in same-package layout. Use Value: High h_FE uniformity and low C_obo reduce output impedance error and improve mirror accuracy over temperature.

Portable Audio Preamp

LED Driver Switch

Use Scenario: Amplifying weak signals from electret microphones in Bluetooth headsets and voice recorders.

IC Role / Device Role / Timing Role: NPN small-signal amplifier in common-emitter configuration with emitter degeneration for linearity.

Use Value: Low 10 dB noise figure and stable h_FE ensure clean gain without introducing audible hiss or distortion at 0.2–2 mA bias points.

Use Scenario: Driving indicator LEDs and status lights in handheld medical devices and IoT sensors.

IC Role / Device Role / Timing Role: Low-side switch controlled by MCU GPIO, turning on/off LED strings with 10–30 mA load current.

Use Value: V_CE(sat) ≤ 0.25 V minimizes voltage drop and self-heating, preserving battery life and enabling direct 3.3 V MCU interface without level-shifting.

Signal Level Shifter

Current Mirror Reference

Use Scenario: Translating logic levels between 1.8 V and 3.3 V domains in mixed-voltage sensor interfaces.

IC Role / Device Role / Timing Role: Active pull-up/pull-down element in open-collector translator circuits with resistive biasing.

Use Value: Tight V_BE(on) = 0.55–0.70 V ensures predictable turn-on threshold and fast edge response for sub-10 ns rise/fall times.

Use Scenario: Building matched current sources in analog front-ends for precision ADC biasing and sensor excitation.

IC Role / Device Role / Timing Role: One leg of a discrete two-transistor current mirror, leveraging matched h_FE and thermal tracking in same-package layout.

Use Value: High h_FE uniformity and low C_obo reduce output impedance error and improve mirror accuracy over temperature.

Equivalent & Alternatives

The following parts are listed as comparable options for similar NPN small-signal transistor applications.

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC847BT	h_FE = 200–450 (lower mid-range gain); V_CEO = 45 V; C_obo = 4.5 pF	Higher voltage margin but reduced gain consistency at low I_C; slightly higher noise figure (~12 dB)	Select when system requires >32 V headroom and can tolerate tighter h_FE tolerance in bias networks.
MMBT3904LT1G	h_FE = 100–300 (narrower range); V_CEO = 40 V; NF = 5 dB (superior noise)	Better noise performance but lower gain necessitates larger base resistors and higher drive current	Prefer for ultra-low-noise preamps where gain stability is secondary to SNR optimization.

Compared with BC847BT and MMBT3904LT1G, the BCW33LT1 offers the highest h_FE range (420–800) among SOT-23 NPN transistors at 32 V rating, balancing low-noise operation (≤10 dB) with robust saturation behavior (V_CE(sat) ≤ 0.25 V), making it optimal for gain-critical, battery-constrained linear stages.

Availability

BCW33LT1 is available at Aetrix Electronics and suitable for portable audio preamps, LED driver switches, signal level shifters, and current mirror references requiring stable component supply and RoHS-compliant SOT-23 packaging.

Supply support for BCW33LT1 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

onsemi (formerly ON Semiconductor) is a global semiconductor supplier specializing in energy-efficient power, analog, sensing, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BCW33LT1 belongs to onsemi's general-purpose bipolar transistor product line, designed for cost-sensitive, space-constrained linear amplification and low-power switching in portable and embedded systems.

FAQ

What is the maximum collector-emitter voltage rating for BCW33LT1?

The BCW33LT1 has a maximum collector-emitter voltage (V_CEO) rating of 32 Vdc, specified under test conditions of I_C = 2.0 mA and I_B = 0. This rating applies to open-base configurations and defines the absolute upper limit before avalanche breakdown occurs. Exceeding this voltage risks permanent device degradation, especially at elevated temperatures.

Does BCW33LT1 support Pb-free soldering processes?

Yes, the BCW33LT1 is manufactured in a Pb-free SOT-23 package and complies with RoHS Directive 2011/65/EU. Its termination finish is matte tin, qualified for standard lead-free reflow profiles (peak temperature ≤ 260°C, 20–40 sec dwell). The BCW33LT1G variant explicitly denotes Pb-free compliance in its part number and datasheet markings.

What is the typical noise figure of BCW33LT1 and under what conditions is it measured?

The BCW33LT1 exhibits a noise figure (NF) of ≤10 dB, measured at V_CE = 5.0 Vdc, I_C = 0.2 mAdc, source resistance R_S = 2.0 kΩ, frequency f = 1.0 kHz, and bandwidth BW = 200 Hz. This value reflects input-referred noise performance in low-frequency small-signal amplification, validated per JEDEC JESD24-A methodology.

Can BCW33LT1 be used in switching applications, and what is its V_CE(sat) performance?

Yes, BCW33LT1 is suitable for low-speed switching applications such as LED control and logic interfacing. Its V_CE(sat) is guaranteed ≤0.25 Vdc at I_C = 10 mAdc and I_B = 0.5 mAdc, ensuring minimal conduction loss and thermal rise. For reliable saturation, maintain I_B/I_C ≥ 0.05 (e.g., 0.5 mA base drive for 10 mA collector load).

What is the thermal resistance of BCW33LT1 on a standard FR-5 PCB?

The BCW33LT1 has a junction-to-ambient thermal resistance (R_JA) of 556 °C/W when mounted on a 1.0 × 0.75 inch FR-5 board at T_A = 25°C. Power dissipation must be derated by 1.8 mW/°C above 25°C ambient, limiting maximum continuous power to 225 mW at room temperature. Thermal performance improves significantly on alumina substrates (R_JA = 417 °C/W).

BCW33LT1 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):: 100 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:: 420 @ 2mA, 5V

Power - Max:: 300 mW

Frequency - Transition:: -

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

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

Supplier Device Package:: SOT-23-3 (TO-236)

BCW33LT1 FAQ

1.How can I place an order for BCW33LT1 through Aetrix?

Please submit a Request for Quotation (RFQ) for BCW33LT1 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 BCW33LT1 reliable?

The price and inventory of BCW33LT1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BCW33LT1 is usually 5 days.

3.What payment methods are accepted for BCW33LT1?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BCW33LT1 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BCW33LT1?

BCW33LT1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BCW33LT1 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 BCW33LT1?

For technical support, including BCW33LT1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BCW33LT1 requirements.

6.How does Aetrix verify that BCW33LT1 is sourced from the original manufacturer or authorized distributors?

All BCW33LT1 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 BCW33LT1 meets industry standards.

7.What is the process for return or replacement of BCW33LT1?

All BCW33LT1 units undergo pre-shipment inspection (PSI). If there is an issue with BCW33LT1, 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 BCW33LT1 part is unused and in its original packaging.

Return procedure for BCW33LT1:

1.Submit a request within 90 days.

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

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