A sensing transistor is provided to supply a detection current in proportion to a current flowing to an output transistor. A shunt resistor is connected between a source of the sensing transistor and the ground. A voltage follower circuit receives a terminal voltage of the shunt resistor and have a base-emitter path of each of transistors in a path between its input and its output. An output voltage of the voltage follower circuit is applied to a current generation resistor. A current drawing circuit draws a control current, which corresponds to a current flowing in the current generation resistor, from a gate control line extending from a gate control circuit to a gate of the output transistor.