FET Transistors

A Field effect transistor (FET) is a three terminal electronic valve - the output (drain) terminal current is controlled by the voltage applied to the input (gate) terminal. Unlike BJTs, conduction in FETs is via majority carriers only. There are several of types of FETs.

Two types of junction field effect transistor (JFET) are shown in Figures 115 and 116. They are either n or p channel.

**Figure 115:** n-channel JFET circuit symbol.
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**Figure 116:** p-channel JFET circuit symbol.
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Figure 117 shows depletion and enhancement types of metal oxide semiconductor field effect transistors (MOSFET). They are either n or p channel.

**Figure 117:** MOSFET circuit symbols.
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The terminals are named: gate (G) at left, source (S) at bottom, and drain (D) at top.

JFET Construction and Operation
MOSFET Construction and Operation

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