Abstract: A current shut-off overload protection circuit useful for fluorescent lamp ballast protection and the like has at least one power transistor for supplying a load current to a circuit load, a protection circuit comprising a current sensing resistance connected for developing a voltage drop related to the circuit load, and a switching diode having a control input operative for turning off the power transistor by removing a bias level, as by grounding the transistor base, responsive to a preset level of the voltage drop such that the load current to the load is switched off upon the load current exceeding a maximum acceptable load current represented by a preset level of the voltage drop.