BC549 Transistor: Features, Alternatives and Datasheet

BC549 is an NPN general-purpose bipolar junction transistor. It carries three pins named emitter, base, and collector and is available in TO-92 and SOT54 package.

BC549 is a low current transistor so the max amount of current that could flow through the Collector pin (Ic) is 100mA, so we cannot connect loads that use above 100mA and load voltage above 30volt using this transistor. BC549 has a reasonable gain value (HEF) from 420 to 800; this value controls the amplification capacity of the transistor.

BC549 transistor contains three layers i.e. two N-doped layers and one P-doped layer. The P-doped layer stands between two N-doped layers. Plus, it contains two PN junctions where one is forward biased and the other is reverse biased.

When no voltage is applied at the base terminal it is considered as grounded. In this case, the transistor acts like an open switch where both emitter and collector remain open.

When voltage is applied at the base terminals it gets biased and draws current which is used to connect other terminals and current starts flowing from collector to emitter terminal.

As this is an NPN transistor, here current flows from collector to emitter when voltage is applied, unlike PNP transistor where current flows from emitter to collector.

Plus, both electrons and holes play a vital role in conductivity. In NPN transistor electrons are majority charge carriers and in PNP transistor holes are majority carriers.

The movement of electrons, however, is faster than the movement of holes, the reason NPN transistors are better and faster than PNP transistors.

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▲Type of Package: TO-92

▲Type of Transistor: NPN

▲Maximum Collector Current(IC): 100mA

▲Max Collector & Emitter Voltage (VCE): 30V

▲Maximum Collector-Base Voltage (VCB): 30volt

▲Max Emitter-Base Voltage (VEBO): 5volt

▲Maximum Collector Dissipation (Pc):  500mW

▲Maximum Transition Frequency (fT): 150 MHz

▲Noise Figure - 1.2 dB

▲Minimum & Max DC Current Gain (hFE): 110 to 800

▲Maximum Storage and Operating temperature Should Be: -65 to +150°C

ON Semiconductor BC549 technical specifications, attributes, parameters and parts with similar specifications to ON Semiconductor BC549.

The BC549 has very low Continuous current of 100mA hence it cannot be used to switch heavy loads. But since it has a base trigger voltage of only 5V it can be easily controlled through 5V GPIO pins of Microcontrollers and Microprocessors. 

So it can be used in places where the load current is less than 100mA. Apart from that the transistor can be used as an amplifier since it has a gain value rom 420 to 800 and a transition frequency of 10MHz

BC549 transistor can also be used in many general purpose applications, for example, it can be used in the audio preamplifier, audio amplifier, and circuits, this transistor can also be used for signal amplification purposes due to its high gain characteristic, the emitter-base voltage is only 5V  which BC549 can be used at the output of the microcontrollers, with the 100mA collector current NPN transistor can be used to control a variety of loads in the electronic circuit like power transistors, relays, MOSFETs, LEDs,  etc.

●Darlington pair

●Sensor circuits.

●Audio Noise filters

●Audio Amplification

●Switching small loads

●Liner audio amplifiers.

●Small signal amplifiers

●Audio Preamplification

●Microcontrollers Output

●LED array sequence controller

●Oscillator and comparator circuits.

●Variety Audio Related Applications

●Astable and Bistable multivibrators.

●Finds application in current mirror circuits.

●Impedance buffering and switching applications.

●Finds application in low noise stages in audio frequency equipment.

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