With the aid of a labelled diagram, describe the operation of a p-channel Junction Field Effect transistors

 When a drain to source voltage Vds is applied between the drain and source terminals and the voltage on the gate is zero, the two PN junctions at the sides of the bar tend to establish a depletion layer. The holes will flow from the source to the drain through a channel between the depletion layers. The size of the depletion layer determines the width of the channel and hence the current conduction through the channel.

When a reverse voltage Vgs is applied between the gate and source terminals , the width of the depletiom layer is increased this reduces the width of the conducting channel hence imcreasing the resistance of the p-type  bar. Hence reducing the current flowing from the drain to source.

When the reverse bias voltage Vgs on the gate is reduced the width of the depletion also decreases and hence increasing the crossectional area of the Channel and hence flow of current by holes increases.