The choice of low-power SMD transistor BVCEO can be determined according to the power supply voltage of the circuit. In general, as long as the BVCEO of the transistor is greater than the highest voltage of the power supply in the circuit.
When the load of the triode is an inductive load, such as transformers, coils, etc., the BVCEO value should be selected carefully. The induced voltage on the inductive load may reach 2 to 8 times the power supply voltage (such as the boost triode in energy-saving lamps).
Generally, the BVCEO of low-power SMD transistor is not lower than 15V, so this parameter does not need to be considered in low-voltage circuits without inductance components.
Generally, the ICM of low-power SMD transistor is between 30 and 50 mA, and small signal circuits can generally be ignored. However, it is necessary to carefully calculate the tubes that drive relays and drive high-power speakers. Of course, we must first understand how many milliamperes the relay pulls in to determine the ICM of the transistor.