Applied positive voltage attracts the electrons within the body towards the gate forms a conductive channel. In n-channel enhancement mode device, we apply positive gate to source voltage because in this mode no conductive channel exists within the transistor. This is known as pinch-off and the voltage at which it occurs is called the pinch off voltage. If the width of the region further expands, then the resistance of the channel become large from source to drain cause the FET turned off like a switch. In n-channel depletion mode device, we always apply a negative gate to source voltage which causes a depletion region to expand in width and narrowing the channel. Here we discuss N channel and P channel FET device in detail. The flow of electrons or holes through the source to drain is generally control by the FET.įield effect transistor is N channel or P channel device operates in two modes i.e. (B) FET Channels:īy applying the voltage across the gate and drain terminals, the electrons or holes starts moving from the source to drain terminal and affects the size and shape of a conductive channel. Its drain to source voltage is denoted by V ds. The current entering the channel through the drain D is denoted by Id.

(iii) Drain: Through this terminal the majority carriers leave the channel i.e. By applying the voltage to G, one can control I g. (ii) Gate: This terminal controls the channel conductivity and is denoted by G. The current entering the channel through the source S is denoted by I s. it act as the source of carriers for the device. (i) Source: Through this terminal the majority carriers enter the channel i.e. (A) FET terminals:įET transistors come in large variety of packages and all of them are susceptible to ESD or electrostatic discharge. At given instant of time, the conductivity of field effect transistor depends on the electrical diameter of the channel. The physical diameter of the channel is fixed but its effective electrical diameter can be varied by the application of a voltage to a control electrode Known as a gate. There are different types of electrodes on both sides of the channel. In Fet, the current flows through the semiconductor path is known as a channel. Fets can be minority carrier charge devices if the current is carried out by minority carriers or majority carrier charge devices if the current is carried out by majority carriers. What is Fet Transistor or Field Effect Transistorįield-effect circuits are used in many areas of electronics involves single carrier type operation i.e. In our previous article, we explain the difference between BJT and FET, Semiconductors electronics Theory. Here we are going to explain FET operation and its types.

robust, cheap, high efficiency and instant operation and can be used in various electronic circuit applications. This type of transistor basically uses an electric field to control the shape and hence the electrical conductivity of a channel of one type of charge carrier in a semiconductor material.įET has various similar characteristics to those of their bipolar transistor counterparts i.e. It is used for amplification of weak signals. FET or field-effect transistor is a three-terminal unipolar semiconductor device.

Field effect transistor