I am trying to learn about n-channel JFETs from David. A. Bell's book. In the transfer characteristics graph, there seem to be two curves as shown. Note that VGS(off) = Vp
As you can see, one curve is drawn for the minimum values of VGS(off) and IDSS and the other curve is drawn for the maximum values of VGS(off) and IDSS. The book shows an excerpt from a data sheet and says that the manufacturer has mentioned the values of minimum and maximum of VGS(off) and IDSS and uses this formula to draw the curves:
I can't understand how there can be maximum and minimum values for the cut-off voltage and the drain current. From the input characteristics graph, I understand that cut-off voltage is nothing but the Pinch-off voltage when there is no voltage applied between the gate and the source(ie) when VGS=0. Now, if there is a maximum and minimum cut off voltage then that means for VGS=0 there are two pinch-off voltages which doesn't make any sense. Also what does having a minimum "saturation" current even mean?