The family tree of FET devices (Figure 1) may be divided into two main branches, Junction FETs (JFETs) and Insulated Gate FETs (or MOSFETs, metal-oxide- semiconductor field-effect transistors). Junction FETs are inherently depletion-mode devices, and are available in both n- and p-channel configurations. MOSFETs are available in both enhancement and depletion modes, and also exist as both n- and p-channel devices. The two main FET groups depend on different phenomena for their operation, and will be discussed separately.