BC108 Pinout, Equivalent, Application, Datasheet

The BC108 is a popular low-noise NPN transistor widely used in audio amplification, signal processing, and switching applications. In this article, we explain its working, detailed BC108 pinout, key features, full datasheet specifications, applications, equivalents, and FAQs. This guide is ideal for students, DIY hobbyists, and electronics engineers working with low-power analog circuits.

Introduction

The BC108 is a high-gain, general-purpose NPN bipolar transistor designed mainly for low-noise amplification and general switching tasks. It is part of the BC107–BC109 transistor family and is well known for its stable operation, wide gain range, and excellent high-frequency response. The metal TO-18 package offers high reliability, making the BC108 suitable for precision analog and audio circuits.

Pin Configuration / Pinout of BC108 Transistor

Understanding the BC108 Pinout Configuration

The BC108 uses a TO-18 metal can package with three terminals: emitter, base, and collector.

Note: DATASHEET DOWNLOAD button is provided end of this article.

BC108 Key Features

• General-purpose NPN transistor
• Excellent for low-noise amplification
• High gain with stable performance
• Suitable for high-frequency applications
• Reliable metal can packaging
• Fast switching characteristics
• Widely used in audio and analog circuits

BC108 Specifications/Characteristics

• Transistor type: NPN bipolar junction transistor
• Collector-emitter voltage (Vceo): 20V
• Collector-base voltage (Vcbo): 30V
• Emitter-base voltage (Vebo): 5V
• Continuous collector current (Ic): 100mA
• Peak collector current (Icm): 200mA
• Total power dissipation (Ptot): 300mW
• Junction temperature (Tj max): 175°C
• Storage temperature (Tstg): –65°C to +150°C
• DC current gain (hFE): 110 to 800
• Transition frequency (fT): 100MHz
• Package type: TO-18 metal can

Key Applications of BC108 Transistor

• Low-noise audio preamplifiers
• General-purpose switching circuits
• Signal conditioning stages
• Oscillators and waveform generators
• Sensor and detector circuits
• Hobby electronics projects
• Analog amplifier circuits

BC108 Equivalent / Alternatives

(Verify pin compatibility before using substitutions)

Common replacements include:

• BC107
• BC109
• BC547 (plastic alternative)
• 2N3904
• 2N2222
• BC237 / BC238 series

More Circuit Layouts

Working Principle of BC108

The BC108 functions as a current-controlled NPN transistor, where a small base current regulates a larger collector current. When used in active mode, it amplifies weak signals in audio and sensor circuits. In saturation mode, it acts as a switch, allowing current flow fully, while in cutoff mode it blocks current. Its high-frequency response and low noise make it ideal for audio preamps, oscillators, and analog signal chains.

Frequently Asked Questions (FAQ)

Q1: What is the difference between BC108 and BC109?
BC109 offers even lower noise, typically used in premium audio applications.

Q2: Can BC108 be replaced with BC547?
Yes, BC547 works as a commonly used plastic substitute.

Q3: Is BC108 good for audio preamplification?
Yes, it is well suited for low-noise audio stages.

Q4: What package does BC108 use?
It comes in a TO-18 metal can package.

Q5: Can BC108 be used for switching?
Yes, it works well as a general-purpose low-power switch.

Conclusion

The BC108 is a versatile, reliable NPN transistor widely used for low-noise amplification, signal conditioning, and switching applications. With strong performance, broad gain range, and a robust metal package, it remains a favorite choice for analog designers and hobbyists. Understanding the BC108 pinout, specifications, and working behavior ensures its correct use in electronic circuit designs.

Datasheet of BC108 Transistor

Click the following Button below to download the datasheet of BC108 :

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