The basic construction of an N-type JFET(Junction Field Effect Transistor) has been described more explicitly in diagram 5.11. The current contains the majority of carriers (In the case of the N channel, the majority of carriers are electrons). When potential difference forms build up between drain and source, current passes through the channel located in the middle of the P region on the bar. One of these contact leads is called source terminal S while the other one is drain terminal D. On both ends of the bar, two ohmic contacts (or direct electrical connections) are fixed. Both P regions are interconnected internally and a single wire just out from it, which is called a gate terminal. These junctions construct two P-N diodes or gates and the place located in the center of the gates is called a channel. Then, two P-type junctions are diffused on opposite sides in the middle part of the N bar (figure a).
For devising an N channel JFET, first, a narrow bar of N-type semiconductor material (usual silicon) is taken. If the arrow sign is towards the gate, it is N channel JFET and if its direction is outward, it is P channel JFET (figure 5.9) Figure 5.9Ī JFET(Junction Field Effect Transistor) is fabricated alongside an N channel or P channel (although an N channel is normally preferred). There is an arrow sign on its electrodes’ gate. Its input resistance is very high and reverse bias is supplied on its gate. In other words, a transistor with two PN junctions on opposite sides of its channels is called JFET. This is the first form of FET which is simply known as JFET(Junction Field Effect Transistor). When Vgs Value is Zero and Vds Value is Increased from ZeroĪ FET with a PN junction between its gate and channel is called junction FET(Field Effect Transistor).Control of Id by Changing the Values of Vg.Junction Field Effect Transistor (JFET).
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