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

onsemi BC817-40LT3

Name: BC817-40LT3
Brand: onsemi
SKU: BC817-40LT3
Price: 2.40 USD
Availability: InStock
Rating: 5 (2 reviews)

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Part No.:: BC817-40LT3

Manufacturer:: onsemi

Category:: Single Bipolar Transistors

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

Datasheet:: BC817-40LT3.pdf

Description:: TRANS NPN 45V 0.5A SOT23-3

Quantity:: RFQ Add To RFQ list

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Product details

Overview

BC817-40LT3 from onsemi is an NPN silicon general-purpose transistor in SOT-23 package, rated for 45 V V_CEO, 500 mA I_C, and DC current gain (h_FE) of 250–600 at I_C = 100 mA / V_CE = 1 V. It delivers low V_CE(sat) ≤ 0.7 V at I_C = 500 mA / I_B = 50 mA and supports switching and linear amplification in compact power management and signal interface circuits.

For engineers reviewing the BC817-40LT3 datasheet, pinout, applications, or equivalent options, key selection criteria include verified h_FE binning (40-series), thermal resistance (R_JA = 556 °C/W on FR-5), safe operating area up to 500 mA, Pb-free SOT-23 packaging, and compatibility with automated surface-mount assembly at 10,000-unit tape-and-reel volume.

Technical Context

The BC817-40LT3 is a discrete NPN bipolar junction transistor optimized for medium-current switching and analog amplification. Its h_FE range (250–600) ensures consistent gain control across production lots, while f_T = 100 MHz enables stable operation in audio-frequency and low-speed digital signal paths.

It operates within −55°C to +150°C junction temperature range and features V_CEO = 45 V, V_CBO = 50 V, and V_EBO = 5.0 V - supporting robust voltage margin in 24 V industrial control and 3.3/5 V logic-level interfacing applications without external protection circuitry.

Key Specifications

Parameter	Value and Actual Design Meaning
V_CEO	45 V - supports reliable operation in 24 V rail systems with ≥2× voltage headroom
I_C (continuous)	500 mA - drives small relays, LEDs, or logic-level MOSFET gates directly
h_FE @ 100 mA / 1 V	250–600 - ensures predictable base drive sizing for saturation in switching designs
V_CE(sat) @ 500 mA / 50 mA	≤ 0.7 V - minimizes conduction loss and self-heating in high-duty-cycle switching
f_T	100 MHz - sufficient for audio amplification and sub-10 MHz digital signal buffering
R_JA (FR-5 board)	556 °C/W - requires minimal copper area for thermal management at ≤300 mW dissipation
P_D (FR-5, 25°C)	225 mW - defines maximum continuous power before derating begins

Pinout & Package

SOT-23 (Case 318, Style 6) - 3-pin surface-mount plastic package measuring 2.90 mm × 1.30 mm × 1.00 mm (L × W × H), optimized for high-density PCB layouts and reflow-compatible assembly.

Pin/Terminal	Circuit Role	Design Meaning
1 (Base)	Current-controlled input terminal	Accepts 50 mA typical base drive to saturate collector current up to 500 mA
2 (Emitter)	Common reference node	Connected to ground or low-side return path; carries full load current
3 (Collector)	Output current terminal	Switches or sources current to load; rated for 45 V reverse bias when off

Key Features

Feature	Design Value
Pb-free SOT-23 package	Complies with RoHS Directive 2011/65/EU and JEDEC J-STD-020 moisture sensitivity level 1 (MSL1)
High h_FE bin (40-series)	Guaranteed minimum h_FE = 250 at I_C = 100 mA, enabling reduced base drive power and smaller bias resistors
Low V_CE(sat)	≤ 0.7 V at I_C/I_B = 10 ensures efficient switching with <100 mW conduction loss at 500 mA
Wide T_J range	−55°C to +150°C operation supports deployment in automotive under-hood and industrial motor-control environments
Proven reliability	Qualified per AEC-Q101 for stress-tested performance in automotive-grade applications

Applications

Industrial Sensor Interface	LED Driver Circuit
Use Scenario: Amplifying low-level signals from RTD or thermistor bridges in programmable logic controllers. IC Role / Device Role / Timing Role: Linear amplifier configured in common-emitter topology with emitter degeneration for stable DC gain. Use Value: High h_FE (250–600) reduces required base bias current, minimizing error from leakage in precision analog front-ends.	Use Scenario: Driving 20–50 mA indicator LEDs in HMI panels and status displays. IC Role / Device Role / Timing Role: Low-side switch with fixed base resistor network controlling LED on/off state. Use Value: V_CE(sat) ≤ 0.7 V limits power loss to <35 mW per LED, eliminating need for heatsinking in space-constrained enclosures.
Relay Driver Stage	Logic-Level Translation
Use Scenario: Activating 12 V/24 V electromagnetic relays in building automation controllers. IC Role / Device Role / Timing Role: Saturated switch interfacing microcontroller GPIO to relay coil with flyback diode protection. Use Value: 500 mA I_C rating handles typical 40–100 mA relay coils with >5× safety margin and fast turn-off due to low C_obo = 10 pF.	Use Scenario: Level-shifting 3.3 V MCU outputs to 5 V or 12 V peripheral inputs in mixed-voltage systems. IC Role / Device Role / Timing Role: Active pull-up stage converting open-drain or weak-drive logic signals to robust voltage rails. Use Value: V_CBO = 50 V and V_CEO = 45 V allow safe operation across 5 V, 12 V, and 24 V domains without clamping components.

Industrial Sensor Interface

LED Driver Circuit

Use Scenario: Amplifying low-level signals from RTD or thermistor bridges in programmable logic controllers.

IC Role / Device Role / Timing Role: Linear amplifier configured in common-emitter topology with emitter degeneration for stable DC gain.

Use Value: High h_FE (250–600) reduces required base bias current, minimizing error from leakage in precision analog front-ends.

Use Scenario: Driving 20–50 mA indicator LEDs in HMI panels and status displays.

IC Role / Device Role / Timing Role: Low-side switch with fixed base resistor network controlling LED on/off state.

Use Value: V_CE(sat) ≤ 0.7 V limits power loss to <35 mW per LED, eliminating need for heatsinking in space-constrained enclosures.

Relay Driver Stage

Logic-Level Translation

Use Scenario: Activating 12 V/24 V electromagnetic relays in building automation controllers.

IC Role / Device Role / Timing Role: Saturated switch interfacing microcontroller GPIO to relay coil with flyback diode protection.

Use Value: 500 mA I_C rating handles typical 40–100 mA relay coils with >5× safety margin and fast turn-off due to low C_obo = 10 pF.

Use Scenario: Level-shifting 3.3 V MCU outputs to 5 V or 12 V peripheral inputs in mixed-voltage systems.

IC Role / Device Role / Timing Role: Active pull-up stage converting open-drain or weak-drive logic signals to robust voltage rails.

Use Value: V_CBO = 50 V and V_CEO = 45 V allow safe operation across 5 V, 12 V, and 24 V domains without clamping components.

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
BC817-40LT1G	Pb-free SOT-23, identical electrical specs, but supplied in 3,000-unit tape-and-reel vs. 10,000-unit for BC817-40LT3G	Same functional use; preferred for low-volume prototyping or small-batch production	Select BC817-40LT1G when reel size must match legacy feeder setup or inventory turnover is slower
MMBT4401LT1G	Higher V_CEO = 40 V (vs. 45 V), h_FE = 100–300 (lower gain bin), same SOT-23 footprint and pinout	Marginally lower voltage headroom and gain consistency; suitable where cost is prioritized over gain stability	Choose MMBT4401LT1G only if design tolerates reduced h_FE spread and operates below 40 V supply rails

Compared with BC817-40LT3, BC817-40LT1G offers identical performance in a smaller reel format, while MMBT4401LT1G trades gain consistency and voltage margin for broader distributor availability - making BC817-40LT3 optimal for high-reliability, medium-volume industrial designs requiring guaranteed h_FE ≥250.

Availability

BC817-40LT3 is available at Aetrix Electronics and suitable for industrial sensor interfaces, LED driver circuits, relay driver stages, and logic-level translation requiring stable component supply and long-term manufacturability.

Supply support for BC817-40LT3 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 delivering energy-efficient, intelligent power and sensing solutions for automotive, industrial, cloud, medical, and IoT applications.

The BC817 series belongs to onsemi's general-purpose bipolar transistor portfolio, designed specifically for cost-sensitive, high-volume switching and amplification tasks in space-constrained PCBs where reliability and consistent parametric binning are essential.

FAQ

What is the maximum continuous collector current for BC817-40LT3?

The BC817-40LT3 supports a maximum continuous collector current (I_C) of 500 mA at T_A = 25°C on FR-5 board. Derating applies above 25°C at 1.8 mW/°C. This rating allows direct driving of relays, LEDs, and logic-level MOSFETs without external current amplification. Always verify actual power dissipation using V_CE(sat) and I_C in the target operating condition before finalizing the BC817-40LT3 in your design.

Does BC817-40LT3 have a Pb-free package?

Yes, BC817-40LT3 is manufactured in a Pb-free SOT-23 package compliant with RoHS Directive 2011/65/EU. The "G" suffix in alternate part numbers (e.g., BC817-40LT3G) explicitly denotes Pb-free construction, and the device meets JEDEC J-STD-020 MSL1 requirements for moisture sensitivity. This makes BC817-40LT3 suitable for lead-free reflow soldering processes used in modern electronics manufacturing.

What is the DC current gain (h_FE) range for BC817-40LT3?

The BC817-40LT3 has a guaranteed h_FE range of 250–600 at I_C = 100 mA and V_CE = 1 V, and 40–250 at I_C = 500 mA and V_CE = 1 V. This "40-series" binning provides higher and tighter gain distribution than BC817-16 or -25 variants, enabling more predictable base resistor selection and improved stability in linear and switching applications using BC817-40LT3.

Can BC817-40LT3 replace BC817-25LT3 in an existing design?

BC817-40LT3 can replace BC817-25LT3 in most cases due to identical pinout, package, and voltage/current ratings - but its higher h_FE (250–600 vs. 160–400) may reduce required base drive current by ~30%. Verify that increased gain does not cause unintended saturation delay or instability in feedback loops. No PCB changes are needed, but re-validate base resistor values and switching timing when substituting BC817-40LT3 for BC817-25LT3.

What is the thermal resistance (R_JA) of BC817-40LT3 on standard FR-5 PCB?

The BC817-40LT3 exhibits a junction-to-ambient thermal resistance (R_JA) of 556 °C/W when mounted on a standard FR-5 board (1.0 × 0.75 × 0.062 in) at T_A = 25°C. This value assumes no additional copper pour or thermal vias. For designs dissipating >150 mW, adding 100 mm² of 1 oz copper connected to the emitter pad via ≥2 thermal vias reduces R_JA significantly - a critical consideration when operating BC817-40LT3 near its 225 mW P_D limit.

BC817-40LT3 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):: 45 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:: 300 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)

BC817-40LT3 FAQ

1.How can I place an order for BC817-40LT3 through Aetrix?

Please submit a Request for Quotation (RFQ) for BC817-40LT3 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 BC817-40LT3 reliable?

The price and inventory of BC817-40LT3 are updated periodically and may fluctuate due to market conditions. Stock and pricing data are typically refreshed every 24 hours. Quotation validity for BC817-40LT3 is usually 5 days.

3.What payment methods are accepted for BC817-40LT3?

We accept Wire Transfer, PayPal, Credit Card, Western Union, MoneyGram, and Escrow for BC817-40LT3 transactions.

Note: Certain payment methods may incur a processing fee.

4.How is shipping managed for BC817-40LT3?

BC817-40LT3 orders can be shipped via leading logistics carriers, including DHL, UPS, FedEx, TNT, or Registered Mail.

Once your BC817-40LT3 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 BC817-40LT3?

For technical support, including BC817-40LT3 datasheets, pinout diagrams, or application guidance, please contact our engineering support team. They can provide detailed documentation and assistance for your BC817-40LT3 requirements.

6.How does Aetrix verify that BC817-40LT3 is sourced from the original manufacturer or authorized distributors?

All BC817-40LT3 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 BC817-40LT3 meets industry standards.

7.What is the process for return or replacement of BC817-40LT3?

All BC817-40LT3 units undergo pre-shipment inspection (PSI). If there is an issue with BC817-40LT3, 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 BC817-40LT3 part is unused and in its original packaging.

Return procedure for BC817-40LT3:

1.Submit a request within 90 days.

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

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