The insulated gate FET (IGFET) differs from other field effect transistors in that it has an insulating layer between the gate and the source-drain channel. The conductivity of the current channel of IGFETs is controlled by a transverse electric field.
Due to the insulating layer between the gate and the current channel, the input resistance is extremely high, reaching into the giga-ohm range. It is controlled by a dynamic control current. Other characteristic values are the extremely short switching times, which are based on the fact that IGFETs have no storage times and no excess charge. In addition, there is the positive temperature coefficient of the channel resistance. Isolated gate FETs are available as n-channel and p-channel types.
Floating gate transistors, also known as FGMOS, belong to the group of isolated gate FETs.