The recommended operating temperature range for BC857BS,135 is -40°C to 150°C.
To ensure stability, it's recommended to use a bypass capacitor (e.g., 100 nF) between the emitter and ground, and to minimize the length of the leads and PCB traces.
The maximum collector current that the BC857BS,135 can handle is 100 mA.
Yes, the BC857BS,135 can be used as a switch, but it's not recommended for high-frequency switching applications due to its relatively slow switching times (e.g., 10 ns).
The choice of resistor values depends on the specific application and the desired current gain. A general rule of thumb is to choose a base resistor that limits the base current to 1/10 of the collector current, and a collector resistor that sets the desired collector current.