Lecture 4¶

Overview of the program¶

1. Presentations

   EE4109 Lecture 3 agenda and introduction

   Presentation

   The presentation “EE4109 Lecture 4 ” shows the agenda.

   Poster

   “CMOS amplifier stages”

   The CD stage (common-drain stage) and the CG stage (common-gate stage) can be regarded as local feedback stages. Their properties can be derived from those of the CS stage and the error reduction capabilities of negative feedback.

   1. The CD stage is a nonenergic unity-gain negative feedback voltage amplifier that has a CS stage as controller. It has parallel output feedback and series input feedback. If the feedback is effective (loop gain much larger than unity) the input impedance exceeds that of the CS stage, while the output impedance is much smaller than that of the CS stage. Since the CD stage is a nonenergic feedback stage, the equivalent input noise sources of the stage equal those of the CS stage (its controller).
   2. The CG stage is a nonenergic unity-gain negative feedback current amplifier that has a CS stage as controller. It has series output feedback and parallel input feedback. If the feedback is effective (loop gain much larger than unity) the input impedance is much smaller than that of the CS stage, while the output impedance exceeds that of the CS stage. Since the CG stage is a nonenergic feedback stage, the equivalent input noise sources of the stage equal those of the CS stage (its controller).

2. Guidance with homework

Study¶

Local feedback stages: Chapter 13.

Homework¶

1. We have seen that the CD stage can be considered as a feedback version of the CS stage. Properties of this stage, such as, the output impedance and the input impedance can be found from circuit analysis. However, they can also be predicted from expected behavioral modifications resulting from application of negative feedback. Please answer the following questions by considering such behavioral modifications.
   1. In which way will the output impedance of a CD stage differ from that of a CS stage if the stage is driven from a low-impedance source (consider an ideal voltage source).
   2. In which way will the output impedance of a CD stage differ from that of a CS stage if the stage is driven from a high-impedance source (consider an ideal current source).
   3. In which way will the input impedance of a CD stage differ from that of a CS stage if its output is shorted.
   4. In which way will the input impedance of a CD stage differ from that of a CS stage if its output is left open.
2. The CG stage can also be considered as a feedback version of the CS stage. Please answer the above questions also for a CG stage.
3. The equivalent-input noise sources of a CS stage can be expressed in terms of the channel noise current (\(S_i=4kT\Gamma g_m\)) and the small-signal T1 matrix coefficients of the CS stage (consider \(I_G=0\)).
   1. In which way and to what extend will the equivalent input noise sources of the CD stage differ from those of the CS stage?
   2. In which way and to what extend will the equivalent input noise sources of the CG stage differ from those of the CS stage?