Q.Explain the classification of FET and the construction of a n-channel JFET.

FETs are classified by type and channel, and an n-channel JFET is built on an n-type bar with two p-type gate regions diffused into it.

[!ANSWER]

FETs are classified into JFET and MOSFET; the JFET is either n-channel or p-channel, and the MOSFET is depletion-type or enhancement-type (each again n- or p-channel). An n-channel JFET is made of an n-type semiconductor bar with two heavily doped p-type gate regions diffused on its opposite sides (two pn junctions); the n-region between them is the channel, the p-regions form the common Gate, and ohmic contacts at the ends form the Drain and Source.

[!TLDR]

FETs split into JFET (n- or p-channel) and MOSFET (depletion or enhancement type, each n- or p-channel); an n-channel JFET is an n-type bar with two p-type gate regions diffused on its sides, the n-region between them forming the channel.

Classification of FET:

A Field Effect Transistor is a unipolar, voltage-controlled device, and the whole family is classified as follows. The two main types are the Junction FET (JFET) and the Metal-Oxide-Semiconductor FET (MOSFET, also called IGFET).

• The JFET is divided by the channel material into the n-channel JFET and the p-channel JFET.
• The MOSFET is divided into the Depletion type and the Enhancement type, and each of these is again available as an n-channel or a p-channel device. This gives the classification tree shown in the figure, with FET at the top branching into JFET and MOSFET, and each branching down to its channel types.

Construction of n-channel JFET:

The construction begins with a bar of n-type semiconductor. On its two opposite sides, two heavily doped p-type regions are diffused, forming two pn junctions on either side of the bar. The n-type region left between these two junctions is called the channel, and it is the path through which charge carriers (electrons) flow. The two p-type regions are connected together internally and brought out as a single terminal called the Gate (G). At the two ends of the bar, ohmic (non-rectifying) contacts are made and brought out as the Drain (D) and the Source (S). During operation, the gate-channel junctions are kept reverse biased, so the gate voltage can control the channel width and hence the drain current.

[!ANSWER]

Classification: FET → JFET (n-channel, p-channel) and MOSFET (Depletion type and Enhancement type, each n- or p-channel). n-channel JFET construction: an n-type bar with two heavily doped p-type regions diffused on opposite sides (two pn junctions); the n-region between them is the channel, the p-regions form the common Gate, and ohmic contacts at the ends form the Drain and Source.