In a JFET, operating above pinch-off voltage, the

Pinch off voltage:

The voltage at which channel will be pinched off i.e. no further movement of carriers from source to drain and the current will be practically constant is called the ‘Pinch off voltage’.

V_P = V_{GS (Cutoff)} = V_{GS (OFF)}

Condition for pinch off saturation:

V_DS = V_GS - V_P

The drain characteristics of the JFET for the different values of V_GS is as shown:

To operate FET as an amplifier, it is operated in the saturation region.

Cutoff: I_D = 0

Linear: I_D increases linearly

Saturation: I_D is constant

Note:

1) I_n ≤ I_DSS always