Here is the datasheet of a transistor: http://www.adafruit.com/datasheets/TIP120.pdf
In maximum ratings, there is a section called "Collector Current (Pulse)". What does that mean in practice?
Lets say this transistor is applied 30V constant DC to its ends. So the max. collector current should not exceed 5A. But if the applied 30V is in the shape of a pulse with lets say %99 duty cycle will the max. current be 8A? Thats what I understand but Im not sure.