With the exception of the body connection, these metallic connection points make up the familiar gate, drain, and source connections shared by all FETs.įigure 2 shows that when sufficient positive voltage is applied from the gate to source connections, then an n-type channel is induced in the p-type body. Layers of metallization or poly-silicon are added where the black bars are shown, which allow for connection to external conductors.įigure 1: A cross-section of an n-channel enhancement-mode MOSFET. A thin, electrically insulating, oxide layer is grown over the surface of the substrate spanning the length between the two n-type regions. A p-type substrate is used for the body, and two heavily doped n-type regions are formed in it. Basic Construction and Operationįigure 1 shows a cross-section of an n-channel enhancement-mode MOSFET. The later sections for p-channel and depletion-mode devices assume the reader has read and understands all the information in the n-channel enhancement-mode section. Because of its ubiquity, the basic construction and operation of a traditional n-channel enhancement-mode MOSFET is explained here first. The enhancement-mode MOSFET (Metal-Oxide-Semiconductor FET) is the most widely used type of FET. The n-Channel (NMOS) Enhancement-Mode MOSFET This approach naturally leads the user to the correct FET types, and eventually to those specific FETs that best fit an application, by allowing filtering based on performance requirements. Fortunately, Digi-Key’s parametric search allows filtering on the specifications common to all FET types. If someone needs a device from one of these other product categories they should know, and those who don’t can avoid them and stick to the more general “ FETs – Single” product category.Īt the time this was written, Digi-Key had more than 39,000 individual part numbers in their “ FETs – Single” product category.

Having these devices in separate categories makes sense for practical reasons. The only other categories that may contain a singly packaged FET are “ JFETs (Junction Field Effect)” and “ RF FETs”. On the Digi-Key Electronics website nearly all singly packaged FETs of any type can be found under the “ FETs – Single” product category.

There are many different types of FETs available, and each type has its own specific variation of materials, configuration, and geometric arrangement. This behavior allows a FET to act as a voltage controlled resistance, amplifier, or switch, and this makes them applicable to both analog and digital electronics. A FET is a three terminal semiconductor device in which the voltage across its gate and source terminals is used to control the current flow between its drain and source terminals.

Fet transistor measurements