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BC107 Transistor: Which Project You Need It For and How to Use It?

Key Features of the BC107 Transistor

The BC107 transistor offers several advantages that make it a popular choice among electronics enthusiasts and professionals. Here are some of its key features:

  1. High Current Gain: The BC107 has a high current gain, typically ranging from 100 to 450. This means that a small current applied to the base can control a much larger current flowing through the collector and emitter.

  2. Low Noise: The transistor exhibits low noise characteristics, making it suitable for audio amplification and other applications where signal integrity is crucial.

  3. Wide Operating Voltage Range: The BC107 can operate with a collector-emitter voltage (VCE) of up to 45V and a collector current (IC) of up to 100mA.

  4. Compact TO-18 Package: The transistor comes in a compact TO-18 metal can package, which provides good heat dissipation and mechanical stability.

BC107 Transistor Pinout

To effectively use the BC107 transistor in your projects, it is essential to understand its pinout. The transistor has three pins: the collector (C), base (B), and emitter (E). The following table shows the pinout of the BC107 transistor:

Pin Symbol Description
1 E Emitter
2 B Base
3 C Collector

It is important to identify the correct pin configuration when connecting the BC107 transistor to your circuit. The emitter is typically connected to the ground or the lower potential, while the collector is connected to the positive supply or the load. The base is used to control the current flow between the collector and emitter.

Typical Applications of the BC107 Transistor

The BC107 transistor finds applications in various electronic circuits. Some of the common uses include:

  1. Audio Amplification: The low noise and high gain characteristics of the BC107 make it suitable for audio amplification circuits, such as preamplifiers and small signal amplifiers.

  2. Switching Circuits: The BC107 can be used as a switch to control the flow of current in circuits. It can be employed in relay drivers, LED drivers, and power control applications.

  3. Signal Processing: The transistor can be used in signal processing circuits, such as filters, oscillators, and modulators.

  4. Temperature Sensing: The BC107 can be configured as a temperature sensor by exploiting its temperature-dependent characteristics.

  5. Voltage Regulation: The transistor can be used in voltage regulator circuits to maintain a stable output voltage.

How to Use the BC107 Transistor?

Now that we have covered the basics of the BC107 transistor let’s dive into how to use it in your projects. We will provide a step-by-step guide and an example circuit to help you get started.

Step 1: Determine the Application

Before using the BC107 transistor, determine the specific application for which you intend to use it. This will help you select the appropriate circuit configuration and component values.

Step 2: Design the Circuit

Based on your application, design the circuit schematic that incorporates the BC107 transistor. Consider factors such as the desired gain, input and output impedance, and power supply requirements.

Step 3: Select Appropriate Component Values

Choose suitable component values for resistors, capacitors, and other elements in your circuit. The values will depend on the desired operating characteristics and the specifications of the BC107 transistor.

Step 4: Assemble the Circuit

Assemble the circuit on a breadboard or PCB, following the schematic diagram. Pay attention to the pinout of the BC107 transistor and ensure proper connections.

Step 5: Test and Troubleshoot

Power up the circuit and test its functionality. Use appropriate test equipment, such as multimeters and oscilloscopes, to measure voltages, currents, and waveforms. If the circuit does not behave as expected, troubleshoot by checking connections, component values, and transistor orientation.

Example Circuit: Simple Audio Amplifier

To demonstrate the use of the BC107 transistor, let’s build a simple audio amplifier circuit. This circuit can be used to amplify weak audio signals from sources like microphones or audio input modules.

Circuit Diagram

[Insert the circuit diagram of the simple audio amplifier using the BC107 transistor]

Components Required

  • BC107 Transistor
  • Resistors: 1kΩ, 10kΩ, 100kΩ
  • Capacitors: 10μF, 100μF
  • Audio input source (e.g., microphone or audio input module)
  • Speaker or headphones
  • 9V battery

Step-by-Step Instructions

  1. Connect the emitter of the BC107 transistor to the ground.
  2. Connect a 1kΩ resistor between the emitter and ground to set the emitter current.
  3. Connect the audio input source to the base of the transistor through a 10μF capacitor. This capacitor blocks any DC component from the input signal.
  4. Connect a 100kΩ resistor between the base and ground to provide a path for the base current.
  5. Connect the collector of the transistor to the positive terminal of the 9V battery through a 10kΩ resistor. This resistor limits the collector current.
  6. Connect the speaker or headphones between the collector and the ground through a 100μF capacitor. This capacitor couples the amplified audio signal to the output while blocking the DC component.
  7. Power up the circuit by connecting the battery, and test the audio amplification by providing an input signal.

Frequently Asked Questions (FAQ)

  1. What is the maximum collector-emitter voltage (VCE) and collector current (IC) for the BC107 transistor?
    The BC107 transistor has a maximum VCE of 45V and a maximum IC of 100mA. It is important to operate the transistor within these limits to avoid damage.

  2. Can I replace the BC107 transistor with another transistor in my circuit?
    While it is possible to substitute the BC107 with another transistor, it is important to ensure that the replacement transistor has similar specifications, such as pinout, voltage and current ratings, and gain characteristics. Always refer to the datasheets of both transistors to verify compatibility.

  3. How do I identify the pinout of the BC107 transistor?
    The BC107 transistor has a standard TO-18 metal can package. The pinout is as follows: Pin 1 is the emitter (E), Pin 2 is the base (B), and Pin 3 is the collector (C). The transistor usually has a small tab or a dot near Pin 1 for easy identification.

  4. What is the purpose of the resistor connected to the emitter in the example audio amplifier circuit?
    The resistor connected to the emitter, known as the emitter resistor, helps to stabilize the transistor’s operating point and sets the emitter current. It also provides negative feedback, which reduces distortion and improves the linearity of the amplifier.

  5. Can I use the BC107 transistor for high-power applications?
    The BC107 transistor is primarily designed for low-power applications. Its maximum collector current rating is 100mA, which limits its use in high-power circuits. For applications requiring higher power handling, you may need to consider transistors with higher current ratings or use multiple transistors in parallel.


The BC107 transistor is a versatile and widely used component in electronic circuits. Its high current gain, low noise, and wide operating voltage range make it suitable for various applications, including audio amplification, switching, and signal processing.

By understanding the key features, pinout, and typical applications of the BC107 transistor, you can effectively incorporate it into your projects. The step-by-step guide and example circuit provided in this article should give you a solid foundation to start experimenting with the BC107 transistor.

Remember to always refer to the transistor’s datasheet for detailed specifications and operating conditions. Additionally, practice proper handling and soldering techniques to ensure the longevity and reliability of your circuits.

With the knowledge gained from this article, you are now equipped to explore the possibilities of the BC107 transistor and create exciting electronic projects. Happy tinkering!