The JFET is a unipolar, voltage-controlled transistor that uses an induced electrical field to control current. The current through the transistor is controlled by the gate voltage. The more negative the voltage, the smaller the current. 

A JFET consists of a length of an n-type or p-type doped semiconductor material called a channel. The ends of the channel are called the source and the drain. The terminal with the arrowhead on its symbol represents the gate. 

In an n-channel JFET, the gate consists of p-type material surrounding the n-channel. In a p-channel JFET, the gate consists of n-type material surrounding the p-channel.