In the invention, pairs of output transistors are provided. An actuator
having an inductance is connected to nodes formed between the pairs of
output transistors. A drive circuit for the actuator is arranged such that
the actuator is driven by causing a drive current to flow into the
inductance. The drive circuit has an overvoltage detection circuit for
detecting whether or not a voltage appearing at the nodes of the output
transistor pairs exceeds a supply voltage by a first predetermined level
and whether or not the voltage becomes lower than a ground level by a
second predetermined level. Output transistors connected to the nodes are
activated by an output from the overvoltage detection circuit.