The BC547 transistor is the most popular after the P2N2222 - a key component for makers
The great news about the the NPN BC547 transistor is its pin compatibility with the popular P2N2222 used in so many tutorials. The BC547 does have the same pinout and it can drive a current limited to 100mA (against 600mA for the P2N2222AG.
This transistor is suited to control small relays, small hobby motor (low power), set of LEDS.... everything requiring more than 10mA (max current on Arduino Pin) and less than 100mA (max current of this transitor)
- Category: Bipolar, low signal
- Vce Max: 45V (Collector Emitter voltage)
- Max Collector current: 100 mA continuous (200 mA peak)
- Vbe Max voltage: 6V (Base-Emitter Max)
- Transition frequency : 300MHz max
- Number of pins: 3
- Height : 5.33mm
- Length : 5.2mm
- Width : 4.19mm
- Type : NPN
More information in the BC547B datasheet.
The NPN transistors are used in so many projects. MC Hobby did make some french publication regarding the NPN P2N2222AG, such tutorial are also suited for the BC547 (the max current is limited to 100mA).