26-09-2013, 03:22 PM
To verify the characteristics of CS Amplifier
INTRODUCTION
So far we have looked at the bipolar type transistor amplifier and especially the common emitter Transistors or FET's for short. These devices have the advantage over bipolar transistors of
having an extremely high input impedance along with a low noise output making them ideal for
use in amplifier circuits that have very small input signals. The design of an amplifier circuit
based around a junction field effect transistor or "JFET", (n-channel FET) or even a metal oxide
silicon FET or "MOSFET" is exactly the same principle as that for the bipolar transistor circuit
used for a Class A amplifier circuit we looked at in the previous experiment. Firstly, a suitable
quiescent point or "Q-point" needs to be found for the correct biasing of the JFET amplifier
circuit with single amplifier configurations of Common-source (CS), Common-drain (CD) or
Source-follower (SF) and the Common-gate (CG) available for most FET devices. These three
JFET amplifier configurations correspond to the common-emitter, emitter-follower and the
common-base configurations using bipolar transistors..