Methods and devices to drive D-mode and E-mode power FETs are described. The disclosure teaches how to apply negative voltages across gate-source of D-mode FETs to turn such FETs off whenever needed. The presented method and devices can also be used in applications where overdriving D-mode FETs to achieve improved on resistance is desired.

Methods and devices to drive D-mode and E-mode power FETs are described. The disclosure teaches how to apply negative voltages across gate-source of D-mode FETs to turn such FETs off whenever needed. The presented method and devices can also be used in applications where overdriving D-mode FETs to achieve improved on resistance is desired.

A GaN logic circuit may include an input node receiving an input voltage, a first pull up transistor pulling up an output voltage in response to the input voltage, and a first depletion mode transistor having a first gate to which a first gate voltage is applied and a second gate to which a second gate voltage is applied. The first depletion mode transistor may control the first pull up transistor in response to a gate voltage difference between the first gate voltage and the second gate voltage. The logic device may further include a capacitor having a first end coupled to the first depletion mode transistor and a second end coupled to the first pull up transistor.

A transistor with excellent electrical characteristics (e.g., on-state current, field-effect mobility, or frequency characteristics) is provided. The transistor includes an oxide semiconductor layer including a channel formation region, a first gate electrode, a second gate electrode, a source electrode, and a drain electrode. The oxide semiconductor layer is between the first gate electrode and the second gate electrode. The oxide semiconductor layer has a pair of side surfaces in contact with the source electrode and the drain electrode and includes a region surrounded by the first gate electrode and the second gate electrode without the source electrode and the drain electrode interposed therebetween.

A transistor with excellent electrical characteristics (e.g., on-state current, field-effect mobility, or frequency characteristics) is provided. The transistor includes an oxide semiconductor layer including a channel formation region, a first gate electrode, a second gate electrode, a source electrode, and a drain electrode. The oxide semiconductor layer is between the first gate electrode and the second gate electrode. The oxide semiconductor layer has a pair of side surfaces in contact with the source electrode and the drain electrode and includes a region surrounded by the first gate electrode and the second gate electrode without the source electrode and the drain electrode interposed therebetween.