The junction gate field-effect transistor (JFET or JUGFET) is the simplest type of field effect transistor. Like other transistors, it can be used as an electronically-controlled switch. They are also used as voltage-controlled resistances. An electric current flows from one connection, called the source, to a second connection, called the drain. A third connection, the gate, determines how this current flows. By applying an increasing negative (for an n-channel JFET) bias voltage to the gate, the current flow from source to drain can be impeded by pinching off the channel, in effect switching off the transistor.
The operation of a JFET can easily be understood by considering a garden hose. The flow of water through a garden hose can be controlled by squeezing it and reducing its cross section; the flow of electric charge through a JFET is controlled by constricting the cross section of the current-carrying channel.
|
