A Complete Guide to The BC639 BJT Transistor
27 October 2023
Ⅰ. Overview of BC639 transistor
Ⅱ. BC639 transistor symbol, footprint and pin configuration
Ⅲ. Technical parameters of BC639 transistor
Ⅳ. Characteristics of BC639 transistor
Ⅴ. Working principle of BC639 transistor
Ⅵ. Maximum ratings of BC639 transistor
Ⅶ. What are the applications of BC639 transistor?
Ⅷ. BC639 transistor usage guide
The BC639 is a versatile NPN transistor that comes in a TO-92 package, offering a collector-emitter voltage rating of 100V and a continuous collector current of 1A. Therefore, the transistor is suitable for medium- and high-voltage switching equipment such as small DC-DC converters and preamplifiers of power amplifiers or mid-stage amplifiers. In addition, it has a maximum DC gain of 160 and a maximum collector power consumption of 625mW, which not only makes it suitable for audio amplifier stages, but also capable of directly driving 2-inch small speakers. Its silicon construction and through-hole mounting configuration add to its reliability and ease of use.
Replacements and equivalents:
• BC537
• BC639G
• BDB01D
• 2N5832
• 2N4410
• 2SC2036
BC639 has 3 pins in total. The pin names and descriptions are as follows:
Pin 1 (Emitter): Current flows through the emitter terminal.
Pin 2 (Collector): Base terminal is the trigger for the transistor.
Pin 3 (Base): Current flow through the collector.
• BC639 is a high current transistor device.
• The BC639 has a DC amplification factor ranging from 40 to 160.
• BC639 is suitable for various applications involving general switching and amplification.
• The BC639 has a maximum collector dissipation of 625mW and a maximum DC current gain of 160, making it ideal for use in audio amplifier stages or as a standalone audio amplifier to directly drive small 2-inch speakers.
• Since the maximum collector-emitter and collector-base voltage of BC639 is 80V, we can easily drive higher voltage loads through this transistor.
When a positive voltage is applied between its base and emitter, this results in an increase in the base current. This seemingly simple action sets off a chain reaction within the amplifier. The increased base current prompts the emitter to release a greater number of electrons. These released electrons are then drawn towards the base, intensifying the flow of current between the base and emitter, which we recognize as the base-emitter current. However, this is just the beginning of the cascading effects of this voltage application. The augmented base-emitter current subsequently leads to an amplification in the collector current–the current that flows between the collector and the emitter. In essence, the application of a positive voltage to the base region acts as a catalyst, compelling the emitter to release more electrons, which in turn enhances the overall current within the circuit.
The following figure shows the maximum ratings of the BC639.
When using the BC639 transistor, we cannot exceed its maximum rating to avoid damaging the device.
• Sensor circuit: It can be used in temperature, displacement, pressure and other sensors to achieve real-time monitoring and data collection.
• Power management: The BC639 transistor has the capability to manage various functions within battery-powered devices, including battery charging and discharging. It empowers us to effortlessly regulate the battery's charging level, discharge duration, and the speed of recharging, thereby enhancing battery longevity and optimizing device efficiency.
• Signal amplification and processing: It can use the amplification function of the triode to amplify weak electrical signals to generate larger electrical signals, which can drive loads or perform other tasks.
• Motor drive: By varying the voltage and current through the motor, the BC639 transistor regulates motor speed, allowing for a wide range of operating speeds. In addition, it can manage the direction of the motor by controlling the polarity of the current, ensuring that the motor can rotate in both forward and reverse directions.
• Wireless communication: It can receive and send signals in wireless communication modules such as Bluetooth and WiFi.
• Power switch: When the input terminal of the BC639 transistor is stimulated, current will flow from the power supply to the output terminal, thus realizing the conduction of the power supply. When the excitation disappears, it cuts off the current and cuts off the power supply.
• Audio amplification: It has the capability to boost low audio signals and power speakers and various audio output devices. This technology finds extensive application in a range of audio equipment, including headphones, speakers, and audio players.
• Relay drive: In automatic control systems, it can also be used as a relay drive circuit to control the start and stop of AC motors or the output of other switching signals.
To begin, it is essential to confirm that the BC639 transistor's storage and operating conditions meet the specified criteria in order to prevent any detrimental environmental factors from impacting its performance and longevity.
Secondly, we need to select the BC639 transistor with appropriate specifications according to the circuit requirements, including maximum power dissipation, maximum collector current and maximum collector-emitter voltage.
In addition, when using the BC639 transistor, we need to pay attention to polarity protection. If the pins are connected incorrectly, the transistor may not work properly or even be damaged. Therefore, before connecting the pins, we carefully check the circuit diagram or datasheet to ensure correct connections.
Finally, we need to pay attention to the heat dissipation issue of the BC639 transistor. Not only do we need to select the appropriate heat sink material and size for optimal heat dissipation, but we also need to consider where the heat sink is installed and fixed to ensure it can effectively dissipate heat away from the transistor surface.
Frequently Asked Questions
1. What is the BC639 transistor?
The BC639 is an NPN bipolar junction transistor (BJT). It is designed for general-purpose switching and amplification applications in electronic circuits.
2. What is the type of package for this BC639 transistor?
The BC639 is an NPN Transistor in a TO-92 package which has a VCE of 100V and a continuous collector current of 1A.
3. What is the replacement and equivalent of BC639 transistor?
You can replace the BC639 with the BC537, BC639G, BC639RL1G, BDB01D, 2N5832, 2N4410 or 2SC2036.
4. What is the maximum current of BC639?
The BC639 transistor has a gain of 40 to 160, which determines the transistor's amplification capacity. The highest current that can be flown through this transistor is 1.5A, which when combined with the gain value makes this transistor an excellent choice for moderate-high voltage applications.
