Patent ID: 8390340

Claim:
A load driving device, comprising: an output transistor having a vertical structure which controls supply of current to an inductive load according to a gate voltage; a first transistor having a horizontal structure which controls a magnitude of a gate voltage across the output transistor; and a second transistor having a horizontal structure which controls application of voltage to a back gate of the first transistor, wherein the output transistor, the first transistor, and the second transistor are transistors of the same conduction type formed in the same substrate, wherein the output transistor has a drain connected to a first power supply through an inductive load, and a source connected to a second power supply that applies a supply voltage different in the first power supply, wherein when an on-state current flows in the output transistor, the second transistor applies the supply voltage applied to the source of the output transistor to the back gate of the first transistor, and wherein when a negative current in a direction opposite to that of the on-state current flows in the output transistor, the second transistor applies the supply voltage applied to the drain of the output transistor to the back gate of the first transistor.