In junction field effect transistor, the drain current can be approximated as:

Explanation:

A junction field effect transistor is a three-terminal semiconductor device in which current conduction is by majority types of carriers i.e., electrons or holes. JFET has high input impedance and low noise levels.

A JFET consists of a p-type or n-type silicon material, containing two p-n junctions at the sides. If the bar is n-type, it is called an n-channel JFET and if the bar is of p-type, it is called a p-channel JFET.

  ID = IDSS

ID = drain current at given VGS

IDSS = short circuit gate-drain current

V_GS= gate-source voltage

 = gate-source cut-off voltage (or) pinch-off Voltage