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.
Where to use BC549 Transistor?
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
Applications
- Switching small loads
- Small signal amplifiers
- Darlington pair
- LED array sequence controller
- Audio Noise filters
2D Model of the Component
If you are designing a PCD or Perf board with this component then the following picture from the Datasheet will be useful to know its package type and dimensions.
- General Purpose Low current and Low voltage NPN Transistor
- Current Gain (hFE), 420 to 800
- Continuous Collector current (IC) is 100mA
- Collector-Emitter voltage (VCEO) is 30 V
- Collector-Base voltage (VCB0) is 30V
- Emitter Base Voltage (VBE0) is 5V
- Transition Frequency 100MHz
- Available in To-92 and SOT54 Package