N-Channel And P-Channel:

An easy drawing of an n-channel JFET and its schematic symbol are shown in figure (a) and (b). The n-type material creates the path for the current. The bulk carriers are electrons. The drain is positive in respect to the source. The gate contains of p-type material. The other, larger portion of p-type material, the substrate, builds a boundary on the side of the channel opposite the gate. The voltage on the gate generates an electrical field which interferes with the flow of charge carriers via the channel. The more negative E_G becomes, the more the electrical field chokes off the current however the channel and the smaller I_D gets.

A p-channel JFET (see figure (c) and (d) shown below) has a channel of p-type semi-conductor. The bulk of charge carriers are holes. The drain is negative by respect to the source. The substrate and gate are n-type material. The extra positive E_G becomes, the more the electrical field chokes off the current via the channel, and the smaller I_D gets.

In engineering circuit diagrams, the n-channel JFET can be acknowledged by an arrow indicating inward at the gate and the p-channel JFET by an arrow indicating outward. The power-supply polarity also shows that type of device is used. The positive drain points out an n-channel JFET and a negative drain points out a p-channel type.

An n-channel JFET almost always can be substituted with a p-channel JFET and the power-supply polarity reversed, and the circuit will still work when the new device has the right specifications.

Figure: (a ) Pictorial diagram of an n-channel JFET, (b) schematic symbol for an n-channel JFET ,(c) pictorial diagram of a p-channel JFET, and (d) schematic symbol for a p-channel JFET.