A driving circuit for a crew protection device to be mounted in a vehicle includes a squib for operating the protection device when a preset amount of electric current is supplied thereto from the DC power source, a pair of first and second transistors connected between the squib and the DC power source, and a transistor control circuit. The transistor control circuit controls the first transistor to pass a first preset amount of electric current if output voltage of the DC power source is higher than a first threshold voltage and to pass an amount of electric current so that the voltage across the first transistor can be set to be lower than a second threshold voltage if output voltage of the DC power source becomes higher than the threshold voltage.