PURPOSE: To improve a commutation critical off-voltage rising rate, a transition current rising rate and conversion to low loss of a gate circuit, and to apply the circuit to the control of various AC power, by constituting a current carrying and conducting mechanism of a unipolar device of only many carriers.

CONSTITUTION: Source electrodes 11, 11' and gate electrodes 12, 12' of two enhancement type MOSFETs10, 10' are connected in common, and electrodes 14, 14' are provided on an area 13 which separates the source area and the drain area, and are connected in common. Also, a resistance 16 is connected between the gate electrode 12' and the source electrode 11', also a control power source 17 is connected through a switch 21, and a series circuit of a load 18 and an AC power source 19 is connected between drain electrodes 15, 15'. Also, a current carrying and conducting mechanism in a device is constituted of a unipolar device, by which a commutation critical off-voltage rising rate, a transition current rising rate and conversion to a low loss of a gate circuit are improved.