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

onsemi BC818-40LT1

Name: BC818-40LT1
Brand: onsemi
SKU: BC818-40LT1
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BC818-40LT1

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BC818-40LT1.pdf

Description:: TRANS NPN 25V 0.5A SOT23-3

Quantity:: RFQ Add To RFQ list

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Inventory:5,301

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Product details

Overview

BC818-40LT1 from onsemi is an NPN silicon general-purpose transistor in SOT-23 package, rated for 25 V V_CEO, 500 mA I_C, and 225 mW P_D on FR-5 board; used in low-voltage switching and amplification circuits such as LED drivers and signal buffering in consumer power management.

For engineers reviewing the BC818-40LT1 datasheet, pinout, applications, or equivalent options, key selection criteria include DC current gain (h_FE = 250–600 at I_C = 100 mA), V_CE(sat) ≤ 0.7 V at I_C/I_B = 10, and thermal resistance of 556 °C/W on FR-5 board.

Technical Context

This discrete NPN transistor operates in linear and saturation regions with guaranteed h_FE ≥ 250 at I_C = 100 mA and V_CE = 1.0 V, and supports switching speeds up to 100 MHz f_T under standard bias conditions. Its V_BE(on) ≤ 1.2 V ensures reliable turn-on with modest base drive.

Designed for surface-mount assembly on FR-5 or alumina substrates, it delivers 225 mW dissipation at 25°C ambient with 1.8 mW/°C derating, and junction temperature range spans −55°C to +150°C - suitable for industrial ambient environments.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	25 V - maximum collector-emitter voltage before breakdown; defines safe operating voltage headroom in low-side switch applications
I_C	500 mA - continuous collector current rating; supports moderate-power loads like relay coils or small solenoids
h_FE	250–600 - DC current gain range at I_C = 100 mA/V_CE = 1 V; enables predictable base drive sizing for switching control
V_CE(sat)	≤ 0.7 V - saturation voltage at I_C = 500 mA/I_B = 50 mA; minimizes conduction loss and self-heating in saturated switch mode
f_T	100 MHz - transition frequency at I_C = 10 mA/V_CE = 5 V; supports audio-frequency amplification and fast digital switching
R_JA	556 °C/W - junction-to-ambient thermal resistance on FR-5 board; determines temperature rise per watt dissipated in PCB-limited thermal design

Pinout & Package

SOT-23 (TO-236) package, case 318, style 6: compact 3-pin surface-mount outline with gull-wing leads, footprint optimized for automated placement and reflow soldering on standard FR-5 PCBs.

Pin/Terminal	Circuit Role	Design Meaning
1	Base	Control input terminal; requires ~50 mA base current to saturate at 500 mA collector load
2	Emiter	Reference node for bias and current return path; connected to circuit ground or common emitter point
3	Collector	Output current terminal; handles switched load current up to 500 mA with ≤0.7 V drop in saturation

Key Features

Feature	Design Value
Pb-free packaging	RoHS-compliant SOT-23 construction with lead finish meeting JEDEC J-STD-020 reflow profile requirements
Guaranteed h_FE binning	h_FE = 250–600 range confirmed per device marking "40" - enables consistent gain-based circuit design without bin sorting
Low V_CE(sat)	≤ 0.7 V at full-rated 500 mA collector current - reduces power loss and thermal stress in high-duty-cycle switching
High f_T	100 MHz transition frequency - supports stable operation in audio preamps and clock buffer stages up to ~10 MHz

Applications

LED Driver Circuit	Microcontroller GPIO Expander
Use Scenario: Driving 20–30 mA indicator LEDs from 3.3 V or 5 V microcontroller outputs. IC Role / Device Role / Timing Role: NPN switch providing current amplification and isolation between MCU pin and LED load. Use Value: V_CE(sat) ≤ 0.7 V ensures >2.3 V forward voltage remains across LED at 20 mA, enabling full brightness with minimal voltage overhead.	Use Scenario: Extending digital output capability of resource-constrained MCUs via discrete transistor arrays. IC Role / Device Role / Timing Role: Low-cost discrete buffer for driving higher-current peripherals (e.g., optocouplers, small relays). Use Value: h_FE ≥ 250 allows 1 mA GPIO drive to switch 250 mA loads - simplifies firmware logic and eliminates need for dedicated driver ICs.
DC-DC Converter Feedback	Industrial Sensor Interface
Use Scenario: Level-shifting and current amplification in optocoupler-based feedback paths of isolated buck converters. IC Role / Device Role / Timing Role: Signal-level NPN amplifier translating error amplifier output into optocoupler LED drive current. Use Value: 100 MHz f_T ensures adequate bandwidth for <100 kHz loop compensation without phase lag degradation.	Use Scenario: Conditioning analog sensor outputs (e.g., thermistor bridges) before ADC input in factory automation modules. IC Role / Device Role / Timing Role: Emitter-follower buffer isolating sensitive sensor nodes from noisy digital sections. Use Value: Low V_BE(on) ≤ 1.2 V and stable h_FE enable accurate unity-gain buffering with <1% linearity error over −40°C to +85°C.

LED Driver Circuit

Microcontroller GPIO Expander

Use Scenario: Driving 20–30 mA indicator LEDs from 3.3 V or 5 V microcontroller outputs.

IC Role / Device Role / Timing Role: NPN switch providing current amplification and isolation between MCU pin and LED load.

Use Value: V_CE(sat) ≤ 0.7 V ensures >2.3 V forward voltage remains across LED at 20 mA, enabling full brightness with minimal voltage overhead.

Use Scenario: Extending digital output capability of resource-constrained MCUs via discrete transistor arrays.

IC Role / Device Role / Timing Role: Low-cost discrete buffer for driving higher-current peripherals (e.g., optocouplers, small relays).

Use Value: h_FE ≥ 250 allows 1 mA GPIO drive to switch 250 mA loads - simplifies firmware logic and eliminates need for dedicated driver ICs.

DC-DC Converter Feedback

Industrial Sensor Interface

Use Scenario: Level-shifting and current amplification in optocoupler-based feedback paths of isolated buck converters.

IC Role / Device Role / Timing Role: Signal-level NPN amplifier translating error amplifier output into optocoupler LED drive current.

Use Value: 100 MHz f_T ensures adequate bandwidth for <100 kHz loop compensation without phase lag degradation.

Use Scenario: Conditioning analog sensor outputs (e.g., thermistor bridges) before ADC input in factory automation modules.

IC Role / Device Role / Timing Role: Emitter-follower buffer isolating sensitive sensor nodes from noisy digital sections.

Use Value: Low V_BE(on) ≤ 1.2 V and stable h_FE enable accurate unity-gain buffering with <1% linearity error over −40°C to +85°C.

Equivalent & Alternatives

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

Alternative Part	Technical Difference	Application Difference	Selection Advice
BC847B,215	Lower I_C rating (100 mA vs. 500 mA); h_FE = 200–450; same SOT-23 package	Not suitable for >100 mA loads; better for low-current signal switching only	Select BC847B,215 when load current ≤ 100 mA and tighter h_FE tolerance is required
MMBT3904LT1G	Same I_C (200 mA typical, 500 mA absolute max); h_FE = 100–300; V_CEO = 40 V	Higher voltage rating but lower guaranteed h_FE; less margin for gain-critical bias networks	Choose MMBT3904LT1G where 40 V V_CEO is mandatory and gain variability is acceptable

Compared with BC818-40LT1, BC847B,215 offers tighter h_FE control but insufficient current capacity for medium-power loads, while MMBT3904LT1G provides higher voltage headroom at the cost of reduced minimum gain - making BC818-40LT1 optimal for 25 V, 500 mA switching with robust gain stability.

Availability

BC818-40LT1 is available at Aetrix Electronics and suitable for LED driver circuits, microcontroller GPIO expansion, DC-DC converter feedback paths, and industrial sensor interfaces requiring stable component supply and RoHS-compliant SOT-23 transistors.

Supply support for BC818-40LT1 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 manufacturer specializing in energy-efficient power, analog, sensing, and connectivity solutions for automotive, industrial, cloud, and consumer markets.

The BC818-40LT1 belongs to onsemi's general-purpose bipolar transistor product line, engineered for cost-sensitive, high-volume applications demanding reliable DC switching and linear amplification in compact SOT-23 packages.

FAQ

What is the maximum continuous collector current for BC818-40LT1?

The BC818-40LT1 is rated for 500 mA continuous collector current (I_C) at T_A = 25°C on FR-5 board. This rating assumes proper PCB thermal relief and derates linearly by 1.8 mW/°C above 25°C ambient. Exceeding this current risks thermal runaway or permanent degradation of the BC818-40LT1 junction.

Does BC818-40LT1 have Pb-free packaging?

Yes, BC818-40LT1 is offered in a Pb-free SOT-23 package compliant with RoHS Directive 2011/65/EU. The "G" suffix variant (BC818-40LT1G) explicitly denotes Pb-free construction, but the standard BC818-40LT1 also meets Pb-free requirements per onsemi's manufacturing specifications.

What is the guaranteed DC current gain (h_FE) range for BC818-40LT1?

The BC818-40LT1 is binned to guarantee h_FE ≥ 250 and ≤ 600 when tested at I_C = 100 mA and V_CE = 1.0 V. This range is marked by the "40" suffix and applies across the full operating temperature range, ensuring predictable base drive requirements for the BC818-40LT1 in production designs.

Can BC818-40LT1 be used in linear amplifier configurations?

Yes, BC818-40LT1 supports linear operation with f_T = 100 MHz and low output capacitance (C_obo = 10 pF), making it suitable for low-noise audio preamplifiers and sensor signal conditioning. However, its V_CE(sat) and thermal limits require careful biasing to avoid distortion or thermal drift in sustained linear mode for the BC818-40LT1.

What is the thermal resistance (R_JA) of BC818-40LT1 on FR-5 board?

The BC818-40LT1 has a junction-to-ambient thermal resistance (R_JA) of 556 °C/W when mounted on a standard FR-5 PCB (1.0 × 0.75 × 0.062 in). This value is critical for calculating junction temperature rise - for example, 100 mW dissipation causes ~55.6°C rise above ambient, directly impacting long-term reliability of the BC818-40LT1.

BC818-40LT1 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):: 25 V

Vce Saturation (Max) @ Ib, Ic:: 700mV @ 50mA, 500mA

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

DC Current Gain (hFE) (Min) @ Ic, Vce:: 250 @ 100mA, 1V

Power - Max:: 225 mW

Frequency - Transition:: 100MHz

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

Grade:: -

Qualification:: -

Mounting Type:: Surface Mount

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

BC818-40LT1 FAQ

1.How can I place an order for BC818-40LT1 through Aetrix?

Please submit a Request for Quotation (RFQ) for BC818-40LT1 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 BC818-40LT1 reliable?

The price and inventory of BC818-40LT1 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC818-40LT1 is usually 5 days.

3.What payment methods are accepted for BC818-40LT1?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC818-40LT1 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC818-40LT1?

BC818-40LT1 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC818-40LT1 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 BC818-40LT1?

For technical support, including BC818-40LT1 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC818-40LT1 requirements.

6.How does Aetrix verify that BC818-40LT1 is sourced from the original manufacturer or authorized distributors?

All BC818-40LT1 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 BC818-40LT1 meets industry standards.

7.What is the process for return or replacement of BC818-40LT1?

All BC818-40LT1 units undergo pre-shipment inspection (PSI). If there is an issue with BC818-40LT1, 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 BC818-40LT1 part is unused and in its original packaging.

Return procedure for BC818-40LT1:

1.Submit a request within 90 days.

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

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