JFET

The JFET (junction gate field-effect transistor) is a long channel of semiconductor material, doped to consist of abundance of positive charge carriers (p-type), or of negative carriers (n-type).

                                                   Figure:  Circuit symbol for an n-Channel JFET

Contacts at each end make the source(S) and drain (D). The gate (G) (control) terminal has doping opposite to that of the channel that surrounds it, that is why there is a P-N junction at the interface. Terminals to connect with the outside are generally made ohmic.

                                                 Figure: Circuit symbol for a p-Channel JFET