Q. Which are the different FET amplifiers?
A FET can be used as a small-signal amplifier by connecting one of its lead to signal ground. The other two leads then serve as the input and the output. The amplifiers constructed with a single FET are named according to which lead is connected to ground. The common source (CS) amplifier has its source connected to ground. The input signal is applied to the gate and the output is taken at the drain.
The input to the Common Drain (CD) amplifier is applied to the gate while the output is taken at the source. For the common gate amplifier (CG), the input is at the source and the output is at the drain.
Source Feedback (SF) amplifier is similar to the CS connection, but there is a resistor connected between the source and the ground. Thus, none of the FET leads are connected to ground. The SF has two output signals, one at the source and one at the drain.