Junction Field Effect Transistor (JFET)

Junction Field Effect Transistor

1. Structure of n-Channel JFET

• The Fig. 3.2.1 shows structure and symbol of n-channel JFET. A small bar of extrinsic semiconductor material, n type is taken and at its two ends, two ohmic contacts are made which are the drain and source terminals of FET.

• Heavily doped electrodes of p type material form p-n junctions on each side of the bar. The thin region between the two p gates is called the channel. Since this channel is in the n type bar, the FET is known as n-channel JFET.

• The electrons enter the channel through the terminal called source and leave through the terminal called  drain. The terminals taken out from heavily doped electrodes of p type material are called gates. Usually, these electrodes are connected together and only one terminal is taken out, which is called gate, as shown in the Fig. 3.2.1.

2. Structure of p-Channel JFET

• The device could be made of p type bar with two n type gates as shown in the Fig. 3.2.2. Then this will be p-channel JFET.

 • The principle of working of n-channel JFET and p-channel JFET is similar; the only difference being that in n-channel JFET the current is carried by electrons while in p-channel JFET, it is carried by holes.