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junction field-effect transistor (JFET)

The Junction Field Effect Transistor (JFET) has an extremely simple structure and a high input resistance, which is lower than that of the MOSFET. This is also the reason why JFETs are only used to a limited extent in discrete circuits.

Junction FET s are available in two versions as p- channel and n-channel JFET. In the n-channel design, the current-carrying channel is n-doped silicon enclosed by the p-doped gate. In the JFET, the pn junction between the gate and n-channel is negatively biased, thereby controlling the current flow between the source and drain. In the p-channel design, the semiconductor materials are reversed accordingly. The p-doped silicon is used for the current carrying channel, the n-doped for the gate.

Structure and circuit diagram of the JFET, top n-doped

Structure and circuit diagram of the JFET, top n-doped

The current- voltage characteristics of JFETs are essentially the same as those of MOSFETs with the exception that the allowable source-gate voltage is 0 V. In the schematic, the two designs are indicated by the direction of the arrow to or from the gate.

In addition to silicon-based JFETs, silicon carbide( SiC) is increasingly being used as a semiconductor material, since the lower power dissipation means that power JFETs can be manufactured for power electronics.

Informations:
Englisch: junction field-effect transistor - JFET
Updated at: 03.05.2011
#Words: 200
Links: metal oxide semiconductor field effect transistor (MOSFET), field effect transistor (FET), channel, indium (In), current
Translations: DE
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