The BC108 is a general-purpose low-power silicon transistor. It is a low-power silicon NPN bipolar junction transistor. It is mostly used as a transistor in almost all types of electronics projects and equipment. BC106 and BC107 are the same as BC108. Moreover, this transistor can be used as a switch and drive load of up to 100mA.
The BC547 is a modern low-cost member of this family, still in a through-hole package, while the BC847 is the surface-mount version.
BC106 BC107 and BC109 are low noise general purpose amplifiers description. They are silicon-type metal case transistors. They are fit for use in driver stages, low noise input stages, and signal processing circuits.
you can replace it with BC547 Transistor Because BC547 is easily and low-cost equivalent of this transistor.
SMD version of the BC109 is MMBTH10 (SOT-23)
BC177, BC178, and BC179 are the compliment of BC10
To use it safely and to increase the life of the transistor do not use it on its absolute MAX ratings and always stay 10% below. The maximum collector current is 100mA so do not drive a load of more than 80mA. The max collector-to-emitter voltage is 20V so remains below 20V. The temperature should not go above -65 °C and below 150°C.
The Datasheet of BC108 NPN transistor is given below please open the given link in a new tab of your browser.