Field Effect Transistor (FET)

The field effect transistor is a three terminal unipolar solid state device in which voltage is controlled by an electric field .

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Types

There are two types of FET -

Junction Field Effect Transistor(JFET)

Metal Oxide Semiconductor Field Effect Transistor(MOSFET)

Voltage Control Device

In case of Field effect transistor the output characteristics are controlled by input voltage . Here input voltage is gate voltage . By changing gate voltage , drain current is controlled. That's why FET is called voltage control device.

Current Controlled Device

Bipolar Junction Transistor (BJT) is called current controlled device because it's output characteristics are determined by the input current . Here collector current is controlled by base current.

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Difference between FET and BJT

Field Effect transistor ((FET)	Bipolar Junction Transistor(BJT)
Voltage controlled device	Current controlled Device
Unipolar device	Bipolar device
Low voltage gain	High voltage gain
High current gain	Low current gain
More expensive than bipolar	Cheap
Difficult to bias	Easy to bias

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