BC549 NPN Transistor

• BC549�is a NPN transistor hence the collector and emitter will be left open (Reverse biased) when the base pin is held at ground and will be closed (Forward biased) when a signal is provided to base pin. It is a low current transistor hence the maximum amount of current that could flow through the Collector pin (Ic) is 100mA, hence we cannot connect loads that consume more than 100mA and load voltage more than 30V using this transistor. BC549 has a decent gain value hfe from 420 to 800; this value determines the amplification capacity of the transistor.
• When this transistor is fully biased then it can allow a maximum of 100mA to flow across the collector and emitter. This stage is called Saturation Region. When base current is removed the transistor becomes fully off, this stage is called as the Cut-off Region.
• 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.

BC549 Equivalent Transistors

• BC547, BC548, BC550

Applications

• 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
• Switching small loads
• Small signal amplifiers
• Darlington pair
• LED array sequence controller
• Audio Noise filters