07-12-2023: Design of application-specific multi-stage negative feedback CMOS amplifiers

Lecture: EE4109-8

Location: Location: Pulse Hall 4

Time: 08:45 - 10:30

A palette with stages

In the previous lectures we discussed:

1. CS stage

2. Balanced stages

3. Feedback stages

4. Balanced feedback stages

We have seen that properties of balanced stages, negative feedback stages, and balanced feedback stages can easily be derived from those of the CS stage. We hereto to consider the effect design techniques (balancing and negative feedback) have on the performance aspects such as noise, drive capability, power efficiency, accuracy, bandwidth and weak nonlinearity.

Design considerations

Controller Design

Presentation

The presentation “Controller Design” discusses the stage type, the most relevant performance aspects and the design parameters of the input stage and the output stage. It also briefly motivates the use of multiple stages.

Preferred controller stages

Presentation

The presentation “Preferred Controller Stages” presents two preferred controller stages

1. The inverting CS-CG cascode stage

2. The noninverting CD-CG stage

These stages show approximate unilateral behavior and maximally contribute to the LP product of a negative feedback amplifier.

Stages’ contribution to LP product

Presentation

The presentation “Contribution of Stages to LP product” discusses the contribution of various amplifier stages to the loop gain-poles product of a negative feedback amplifier.

It also shows a way to calculate the absolute minimum number of stages in the controller of a negative feedback amplifier that are required to fullfill the bandwidth requirements of the amplifier.

Miller Effect and Cascode Stages

Presentation

The presentation “Pole-splitting and Cascode stages” discusses the pole-splitting in RC-loaded CS stages. If such stages are applied in the controller of a feedback amplifier, pole-splitting may result in a reduction of the loop gain-poles product of the amplifier. Pole-splitting can be eliminated by cascading the CS stage with a current follower (e.g. CG stage). The cascade connection of the CS stage and a CG stage is usually referred to as a cascode stage.

Study

Chapter 5.3, Chapter 13.2.3, Chapter 14.2.6

Design approach

The design approach for application-specific negative feedback amplifiers will be elucidated with the aid of the poster Design of application-specific multi-stage feedback CMOS amplifiers </posters/SED-CMOS-order.pdf>`_.

Poster

1. CMOS stages for controller design

2. Design of application-specific multi-stage feedback CMOS amplifiers

Group exercise

1. Sketch multiple architectures for the signal path of the hearing-loop receive amplifier A1, using two-stage and three-stage controller architectures and discuss pros and cons of the different structures in the goup and with the tutors.