# Transistor current limit

Suppose the DC motor has a peak current of 500ma and after that it drops to 100ma, the transistor can switch continuously 200ma.

If I limit the current of the transistor from the base current to 100ma, for some reason could the transistor consume a higher peak than that when starting the motor or would it be limited to 100ma?How effective is limiting hfe gain against inrush currents?

• if the base current is 100 mA, the motor current will be effectively unlimited. I'm not familiar with the BC548, but if it's anything like the general purpose transistors I've used, it has a β on the order of 100, so the collector current would be limited to about 10 A. Jan 13, 2021 at 4:45
• "If I limit the current of the transistor from the base current to 100ma" - Do you mean limit Collector current to 100mA by applying the necessary Base current to get it, or apply 100mA to the Base? Jan 13, 2021 at 5:06
• Suppose the hfe is 100 to 12v and 100ma of collector, on the base I applied 1ma Jan 13, 2021 at 10:34
• If you never supply the 500mA that the motor needs at the start then the motor may not turn at all. Jan 13, 2021 at 13:34
• Limited the motor with resistor to work at 100ma maximum I had satisfactory performance! My concern is to protect from inductive peaks in very short times that destroy my transistor! I know that I should dimension the circuit, but I would like to limit the components too, I understand today that a transistor limited to 100ma of current between collector and emitter would eliminate the use of a resistor Jan 13, 2021 at 14:28