BC 818K-40 Infineon Transistor BJT NPN (SOT23 (3-Pin)) In Stock
Infineon BC 818K-40 NPN bipolar transistor rated at 500 mA collector current and 25 V collector-emitter voltage in a compact 3-pin SOT-23 package. The high-gain K group provides an hFE range of 250 to 600 for signal amplification and reliable low-side switching. Surface-mount SOT-23 footprint with 300 mW power dissipation suits portable consumer and industrial PCB designs.
- Manufacturer
- Infineon
- Package
- SOT23 (3-Pin)
- Pin Count
- 3
- Lifecycle
- ACTIVE
- Datasheet
- N/A
- Category
- Transistor BJT NPN
- RoHS
- Compliant
- Lead Time
- 3–7 business days
- Shipping
- DHL Express · Worldwide
What are the key features of BC 818K-40?
- 500 mA collector current and 25 V VCEO rating enables reliable low-side switching of LED strings, relays, and small inductive loads in 5 V to 12 V circuits
- High K-group gain (hFE 250 to 600) delivers superior current amplification for pre-amplifier stages, sensor signal conditioning, and Darlington driver configurations
- Compact 3-pin SOT-23 package with 300 mW power dissipation provides a minimal PCB footprint ideal for battery-powered IoT nodes and portable instrumentation
What is BC 818K-40 used for?
The Infineon BC 818K-40 NPN transistor excels as a low-side switch and signal amplifier in LED driver circuits, relay coil drivers, and small-motor control stages operating from 3.3 V to 25 V supply rails. Its high hFE of 250 to 600 and 500 mA collector current rating make it effective for driving inductive loads and amplifying weak sensor signals in industrial control and consumer electronics. The SOT-23 package simplifies integration into battery-powered IoT nodes, wearables, and compact instrumentation where board space is at a premium.
Compliance & Regulatory
| RoHS Status | Compliant |
| Lead-Free | Yes (Pb-Free) |
What are equivalent replacements for BC 818K-40?
No known alternates. Submit an RFQ and our team can suggest alternatives.
Frequently Asked Questions
What are the collector current, voltage, gain, and power dissipation ratings of the Infineon BC 818K-40?
The BC 818K-40 is rated for a maximum collector current of 500 mA and a collector-emitter voltage (VCEO) of 25 V. Its K-group classification provides a high hFE gain range of 250 to 600, and the SOT-23 package supports up to 300 mW power dissipation, making it a versatile NPN transistor for both switching and linear amplifier applications in low-voltage circuits.
How can the BC 818K-40 drive an LED string or relay coil from a 3.3 V microcontroller logic output?
With an hFE of 250 to 600, the BC 818K-40 typically needs only 1 mA of base current to switch 100 mA through an LED string or energize a small relay coil, allowing a 3.3 V logic output with a base resistor in the 1 kohm to 10 kohm range to fully saturate the transistor. The 25 V VCEO rating gives adequate headroom when switching 5 V or 12 V load circuits, and the SOT-23 package keeps the PCB area to a minimum.
When is the BC 818K-40 high-gain variant preferred over a standard BC818-16 for a sensor pre-amplifier design?
The BC 818K-40 K-group is preferred when a design demands high transistor gain (hFE 250 to 600) versus the BC818-16's lower gain range of 100 to 250, reducing the base drive current required for amplifying low-level signals from sensors or microphones. Operating up to 500 mA and 25 V, the K group ensures lower distortion and better signal fidelity in linear pre-amplifier stages, Darlington configurations, and current-mirror circuits within a compact SOT-23 package.
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