Because of the insulated gates, IGBTs require a continuous gate circuit in order to sustain gate current. There are four basic types of gate drivers. High-side gate drivers are used to drive power-MOSFETs or IGBTs that are connected to a positive supply and not ground referenced (floating). Conversely, low-side gate drivers are used to drive power-MOSFETs and IGBTs that are connected to a negative supply. Dual gate or half-bridge gate drivers have both low-side and high-side gates. Three-phase drivers have three independent low-side and high-side referenced output channels. Typically, gate drivers have 1, 2, or 4 output channels, and the output voltage can either be inverted or non-inverted.