Joining solutions at the pinch-off point in “field-effect” transistor

In a unipolar “field-effect” transistor with the drain connection biased beyond “pinch-off” in respect to the gate, the potential distribution is difficult to determine by analytic methods. Approximate solution may readily be obtained except near the “extrapolated pinch-off point.” In this publication, an approximate solution is obtained valid over the entire length of the channel.