Q. Give an introductive notes about FET amplifier ?

 The small signal models for the common source FET can be used for analyzing the three basic FET amplifier configurations: (i) Common source (CS), (ii) Common drain (CD) or Source-follower, and (iii) Common gate (CG). The CS amplifier which provides good amplification is most frequently used. The CD amplifier with high input impedance and near- unity voltage gain is used as a buffer amplifier and the CG amplifier is used as high frequency amplifier. The small signal current-source model for the FET in CS configuration is shown down (fig ); the voltage-source model can be derived by finding the Thevenin's equivalent for the output part.