The BC639 transistor is a very versatile transistor that can be used in many different applications. This transistor can be used to switch moderately high voltage devices, like a small DC-DC converter, or a pre or mid amplifier stage of a power amplifier, generally, a power amplifier uses something like 60 to 120V DC this transistor can be useful for this kind of applications. The component is cheap and easy to work with so it is best suited when choosing a random switching device. When this transistor is in a biased condition, then it can allow a maximum current of 1A across CE(Collector-Emitter) Junction, this state of the transistor is called the saturation state, and driving a load that consumes more current than 1A may damage the device permanently, also during the design process, you need to be aware that the maximum dissipation of this device is 1W, power more than that can damage the device.

As you already may know, a transistor is a current-controlled device so when the base current is removed the transistor becomes fully off, in this stage the transistor is working in its cut-off region/cut-off state and no current flows through the C-E junction. The BC639 transistor has a gain of 40 to 160, this value determines the amplification capacity of the transistor, the peak current that can be flown through this transistor is 1.5A which combined with the gain value makes this transistor a perfect choice for moderate-high voltage application.

Under normal circumstances and without external influence, the base of an NPN transistor will be 0V. As we all know, based on the working principle of an NPN transistor; having 0 voltage at the base puts an NPN transistor in a high resistance state. By characteristic a small amount of current needs to flow out of the base of the transistor to completely turn on the device, for this device you can see, in order to flow 1000mA of current through the collector to emitter, 50mA of current needed to flow through the base of the transistor.

• Bi-Polar NPN, high voltage Transistor
• DC Current Gain (hFE) is 160 maximum
• Continuous Collector current (IC) is 1A
• Emitter Base Voltage (VBE) is 5V
• Base Current (IB) is 100mA maximum
• Maximum Collector-Base Voltage |Vcb|: 50 V
• Collector Dissipation: 1 W
• Transition Frequency:100 MHz
• Collector Capacitance 20pF
• Operating Junction Temperature Max (Tj): 150 °C
• Available in TO-92 Package