Description

Bipolar Transistors BC817 45V 0.3W 0.5A NPN SOT-23 – Compact NPN Transistor for General-Purpose Switching

The BC817 Bipolar Transistor is a widely used NPN silicon transistor designed for general-purpose switching and low-power amplification applications. With a 45V collector-emitter voltage rating, 0.5A collector current, and 0.3W power dissipation, the BC817 delivers reliable electrical performance in a compact SOT-23 surface-mount package.

Thanks to its small size, low cost, and dependable characteristics, the BC817 transistor is commonly found in consumer electronics, embedded systems, industrial control circuits, automotive electronics, and signal switching applications. It is especially suitable for modern PCB designs where space efficiency and automated assembly are important.

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NPN Bipolar Junction Transistor Design

The BC817 is an NPN bipolar junction transistor (BJT). In an NPN transistor, a small base current controls a much larger collector-emitter current, allowing efficient switching and amplification of electrical signals. This makes the BC817 ideal for interfacing low-power logic circuits with higher-current loads.

NPN transistors are widely preferred due to:

• Simple biasing methods

• Fast switching performance

• Broad compatibility with digital and analog circuits

Learn more about how bipolar junction transistors work:
https://www.allaboutcircuits.com/textbook/semiconductors/chpt-4/bipolar-junction-transistors/

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45V Collector-Emitter Voltage Rating

With a maximum collector-emitter voltage (VCE) of 45 volts, the BC817 can safely operate in low- to medium-voltage circuits. This voltage rating provides sufficient margin for applications involving 12V, 24V, and similar power rails, protecting the transistor from breakdown due to voltage spikes or transients.

This makes the BC817 suitable for:

• Logic-level switching

• Low-voltage power control

• Signal amplification circuits

Understanding transistor voltage ratings:
https://www.electronics-notes.com/articles/electronic_components/transistors/transistor-voltage-ratings.php

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0.5A Collector Current Capability

The BC817 supports a maximum collector current of 0.5A, allowing it to drive small motors, relays, LEDs, and other moderate loads. Despite its compact SOT-23 package, the transistor provides adequate current handling for many switching applications.

This current capability makes it ideal for:

• Relay drivers

• LED switching circuits

• Small solenoids and actuators

• Interface circuits between microcontrollers and loads

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0.3W Power Dissipation

With a total power dissipation rating of 0.3 watts, the BC817 is designed for low-power applications where efficient operation and minimal heat generation are required. Proper PCB layout and thermal management help ensure safe operation within this power limit.

For higher reliability, designers typically operate the transistor below its maximum dissipation rating, extending service life and improving stability.

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SOT-23 Surface-Mount Package

The SOT-23 package is one of the most popular surface-mount transistor packages used in modern electronics. It offers several advantages:

• Extremely compact footprint

• Compatibility with automated pick-and-place assembly

• Ideal for high-density PCB layouts

• Reduced parasitic inductance

The BC817’s SOT-23 form factor makes it a perfect choice for compact devices such as IoT modules, portable electronics, and embedded systems.

More about SOT-23 packaging:
https://www.electronics-notes.com/articles/electronic_components/packages/sot23.php

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Reliable Switching and Amplification Performance

The BC817 transistor is optimized for fast and reliable switching, making it suitable for digital logic control and signal processing. It also provides stable gain characteristics, allowing it to function effectively in small-signal amplification applications.

Its predictable behavior and consistent specifications across manufacturers make it a trusted choice for mass-production electronics.

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Wide Range of Applications

The BC817 NPN transistor is commonly used in:

• Microcontroller interface circuits

• Logic-level switching

• LED drivers

• Relay and load control circuits

• Signal amplification

• Consumer electronics

• Industrial automation systems

• Automotive electronic modules

• Battery-powered devices

Its versatility and compact size make it suitable for both new designs and replacement applications.

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Key Specifications Overview

• Transistor type: NPN Bipolar Junction Transistor

• Model: BC817

• Collector-Emitter Voltage (VCE): 45V

• Collector Current (IC): 0.5A

• Power Dissipation (PD): 0.3W

• Package type: SOT-23

• Mounting type: Surface-mount (SMD)

• Application: Switching and amplification

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Why Choose the BC817 NPN Transistor?

The BC817 45V 0.3W 0.5A NPN transistor offers an excellent combination of compact size, reliable electrical performance, and cost-effectiveness. Its SOT-23 package makes it ideal for modern surface-mount designs, while its electrical ratings support a wide range of low-power switching and amplification tasks.

Whether used in consumer electronics, industrial systems, or embedded designs, the BC817 remains a dependable and widely adopted solution.