The CG stage
Feedback stages are negative feedback amplifiers with a single-stage controller. The controller can be a biased CS stage or one of its balanced versions.
Presentation
The name Common Gate Stage refers to the fact that the gate of the MOSFET is taken as the common terminal for the input and the output port of this stage. In analog electronics it is common practice to name amplifying stages according to their topology (CD stage, CG stage, cascode stage), their inventor (Gilbert Gain Cell, Wilson Mirror), their application (OPAMP), or their function (OTA, current mirror).
In structured electronic design, however, we like to emphasize that all amplifier stages can be obtained from the basis CS-stage through application of error-reduction techniques. From a viewpoint of design this has the advantage that the measure that has been taken to improve certain performance aspects of the basic stage is made explicit. In other words: the error reduction capabilities of the applied technique fully explain in which way and to what extend the properties of the modified stage differ from those of the CS stage.
The presentation “Common Gate Stage” shows that the CG stage can be viewed upon as a nonenergic feedback stage with a CS stage controller. By doing so, all performance aspects of the CG stage can be related to those of the CS stage, simply by considering the behavioral modifications resulting from the application of negative feedback.
Video