The Field Effect Transistor (FET)

The field effect transistors or FETs are particularly interesting and they can be of two types:

- The Junction Field Effect Transistor or JFET and
- The Metal-Oxide Semiconductor Field Effect Transistor (MOSFET).

These devices have a high input impedance (10¹² ohms) and they are controlled by voltage. Both devices are used as an amplifier or a switch in analog and digital circuits.

Its electrical characteristics of the JFET and the MOSFET are similar although their technology and physical structure are totally different.

Advantages of FET

1) They are devices controlled by voltage with a very high input impedance (10⁷ to 10¹² ohms).
2) FETs generate a lower noise level than the Bipolar Junction Transistor (BJT).
3) FETs are more stable than BJT with temperature
4) FETs are easier to manufacture than the BJT, because they require fewer steps to be built and they allow more integrated devices in the same IC.
5) FETs behave like resistors controlled by voltage for small drain-source voltage values.
6) The high input impedance of FET allows them to withhold loads long enough to allow its usage as storage elements.
7) Power FETs can disipate higher power and can switch very large currents.

Disadvantages of FET

1) FETs have a poor frequency response due to its high input capacitance.
2) FETs have a very poor linearity, and generally they are less linear than BJT.
3) FETs can be damaged due to the static electricity.

FET electrical characteristics >>

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