Patent ID: 7667939

Claim:
A bus driver device, comprising: a bus driver circuit connected to a bus line; a power supply wiring; an overvoltage protection section connected between the bus line and the power supply wiring, which has an overvoltage protection function for the bus line; and a switching circuit for on/off-controlling the overvoltage protection function based on a voltage of the bus line and a voltage of the power supply wiring, wherein the switching circuit comprises; a first transistor connected between the power supply wiring and the overvoltage protection section; and a control circuit for on/off-controlling the first transistor based on the voltage on the bus line, and wherein the overvoltage protection section comprises: a second transistor connected between the bus line and the first transistor, which has a back gate; and a third transistor connected between the back gate of the second transistor and the power supply wiring.