Common Circuit Application(Voltage-Controlled Resistor)

V_GS must be between zero and V_GS.off .

Common Circuit Application(Source Follower)

The simple source follower is shown below. The improved version is shown at the right. The lower JFET forms a current source. The result is that V_GS is held constant, removing the defects of the simple circuit.

Common Circuit Application(Current source)

The drain current is set by R_S such that V_GS = I_DR_S. Any value of current can be chosen between zero and I_DSS.