HIGH-VOLTAGE DEPLETION-MODE CURRENT SOURCE, TRANSISTOR, AND FABRICATION METHODS

A depletion-mode current source having a saturation current of sufficient accuracy for use as a pre-charge circuit in a start-up circuit of an AC-to-DC power converter is fabricated using an enhancement-mode-only process. The depletion-mode current source can be fabricated on the same integrated circuit (IC) as a gallium nitride field-effect transistor (FET) and resistive and capacitive components used in the start-up circuit, without affecting the enhancement-mode-only fabrication process by requiring additional masks or materials, as would be required to fabricate a depletion-mode FET on the same IC as an enhancement-mode FET. The current source includes a resistive patterned two-dimensional electron gas (2DEG) or two-dimensional hole gas (2DHG) channel coupled between two terminals and one or more metal field plates extending from one of the terminals and overlying the patterned area of the channel, the field plates being separated from the channel and from each other by dielectric layers.