Question

When an N-channel JFET reaches pinch-off, the increase in the drain to source voltage results in shifting of the pinch-off position towards the ___________

(a) Gate

(b) Drain

(c) Source

(d) Does not shift

I got this question in unit test.

My query is from Characteristics of JFET topic in division FET Amplifiers of Analog Circuits

Answer 1

Correct answer is (c) Source

Best explanation: Pinch off is said to be reached if the drain to source voltage is equal to the difference between the gate to source and the threshold voltage. So, this pinch off happens at a certain distance from the source and the gradual decrease in the channel length will happen faster if the voltage along the channel length increases faster. It can be readily observed that equality is reached at a distance less than the previous case and hence the pinch-off is shifted towards the source.