Q. How does current flow through the channel of a JFET after pinch off?
It is seen that above the pinch off voltage at a constant value of VDS (saturation drain current, ID increases with an increase of VGS (gate voltage). Hence, a JFET is suitable for use as a voltage amplifier, similar to a transistor amplifier.
Even at VDS=VP (pinch off voltage), the drain current is not reduced to zero. If the drain current is to be reduced to zero, the ohmic voltage drop along the channel should also be reduced to zero. Further, the reverse biasing to the gate source PN junction essential for pinching off the channel would also be absent.
The drain current ID is controlled by the electric field that extends into the channel due to reverse biased voltage applied to the gate; hence, this device has been given the name Field Effect Transistor.