JFET
full spelling ： Junction gate Field Effect Transistor
JFET is an acronym for junction gate field-effect transistor. It is a type of field effect transistor. The flow of electric charge through a JFET is controlled by constricting the cross section of the current-carrying channel.
The junction gate field-effect transistor consists of a long channel of semiconductor material. This material is doped so that it contains abundance of positive charge carriers (p-type), or of negative charge carriers (n-type). There is a contact at each end; source and drain. 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. JFET can be used as an electronically-controlled switch and it are also used as voltage-controlled resistances.