CoolGaN™ Bidirectional Switch 40 V G3 in WLCSP, 9 mΩ The IGK120B041S is a 40 V normally-off bidirectional power transistor housed in a small WLCSP 1.2x1.7 package, enabling high power density designs. Thanks to its very low on-state resistance, it is the ideal choice for reliable performance in demanding applications requiring bidirectional blocking capability such as load switch.