| 摘要 |
The present invention is provided with: a comparator (124) that compares with each other an applied voltage applied between the drain and the source of a field effect transistor, and a reference voltage for detecting noise generated between the drain and the source of the field effect transistor; and a gate voltage switching circuit (130) that switches a voltage to be applied between the gate and the source of the field effect transistor to a second voltage from a first voltage when an output state of the comparator (124) transits from a state wherein the applied voltage between the drain and the source is less than the reference voltage to a state wherein the applied voltage between the drain and the source is equal to or more than the reference voltage, in the cases wherein the field effect transistor is in the off-state. When a threshold voltage of the field effect transistor is represented by Vth, the first voltage is represented by V1, and the second voltage is represented by V2, the relationship of Vth>V1>V2 is satisfied, and the second voltage is a negative voltage. |
