This document discusses the JFET (junction field-effect transistor). It begins by defining a field-effect transistor as a device where the electric field controlling current flow is perpendicular to the direction of current. It then describes the structure of an n-channel JFET, showing how a p-type channel is created between two n-type regions. Key features of the JFET are that it is a voltage-controlled, majority-carrier device with higher input impedance and lower output impedance than BJT transistors. The document provides equations for calculating the pinch-off voltage and expressions for transconductance. It concludes by outlining some applications of JFETs in RF amplifiers, measuring instruments, oscillators, and digital circuits