Abstract: A speed-up circuit is configured to be provided between a power supply terminal and a gate of a semiconductor switching element. An impedance element is configured to be provided between a signal input terminal and a node, the node being between the speed-up circuit and the gate of the semiconductor switching element. In the speed-up circuit, a second field effect transistor is connected in series to a first field effect transistor and is configured to be connected to the gate of the semiconductor switching element. The impedance element has an impedance higher than an impedance of the speed-up circuit when both the first field effect transistor and the second field effect transistor are in an ON state.

Abstract: A substrate electric potential stabilization circuit is configured to be connected to a bidirectional switch element including a first main electrode, a second main electrode, and a backside electrode. The stabilization circuit includes a first switch connected to the first main electrode and the backside electrode in series between the first main electrode and the backside electrode, a second switch connected to the second main electrode and the backside electrode in series between the second main electrode and the backside electrode, and a through-current prevention circuit configured to prevent the first switch and the second switch from being turned on simultaneously. The substrate electric potential stabilization circuit prevents a through-current flowing in this circuit.

Abstract: A bidirectional switch module includes a plurality of bidirectional switches and a mount board. Each of the plurality of bidirectional switches includes a first source electrode, a first gate electrode, a second gate electrode, and a second source electrode. On the mount board, the plurality of bidirectional switches are mounted. In the bidirectional switch module, the plurality of bidirectional switches are connected in parallel.

Abstract: A speed-up circuit is configured to be provided between a power supply terminal and a gate of a semiconductor switching element. An impedance element is configured to be provided between a signal input terminal and a node, the node being between the speed-up circuit and the gate of the semiconductor switching element. In the speed-up circuit, a second field effect transistor is connected in series to a first field effect transistor and is configured to be connected to the gate of the semiconductor switching element. The impedance element has an impedance higher than an impedance of the speed-up circuit when both the first field effect transistor and the second field effect transistor are in an ON state.

Abstract: A nitride semiconductor device includes: a stacked structure portion having an active region; first and second main electrodes extending in a first direction; and a lead-out line (second lead-out line) electrically connected to the second main electrode and extends to one side in the first direction. The first main electrode has a first tip at an end which is on the side to which the lead-out line extends. The second main electrode has a second tip at an end which is on the side to which the lead-out line extends, and has, at a second tip-side in the first direction, a tapered portion having a width in a second direction which decreases with decreasing distance to the second tip. The lead-out line has a region projecting in the second direction from the tapered portion, and the first tip does not project further in the first direction than the second tip.