Feedback modeling#
Modeling of negative feedback circuits#
Two-step design of negative-feedback amplifiers
The design of negative-feedback amplifiers can be performed in two steps:
The design of the ideal gain of the amplifier. This comprises the design of the structure of the amplifier with feedback networks and nullors as ideal controllers.
The design of the controller(s) (also error amplifiers)
This two-step design method requires that butgets for performance limitations of the amplifier are split into error budgets for the feedback networks and error budgets for the controller.
Presentation
The presentation Two-step design of negative feedback amplifiers shows that a feedback model that supports the two-step design of negative feedback amplifiers will tell us in which way and to what extent performance limitations of the amplifier are affected by performance limitations of the controller(s).
Presentation in parts
Two-step design of negative feedback amplifiers (parts)
Video
Two-step design of negative feedback amplifiers
Study
Chapter 10.1
Feedback model of Black
In 1927, Black built the first negative feedback amplifier. The feedback model of Black is commonly used to evaluate the dynamic performance of negative feedback systems. However, Black's feedback model is not optimally suited for the analysis of dynamic behavior of electronic feedback amplifiers and providing meaningful design information from such analysis.
Presentation
The presentation Feedback model of Black introduces the feedback model of Black and shows its limitations for the analysis of electronic feedback circuits.
Presentation in parts
Feedback model of Black (parts)
Video
Study
Chapter 10.2
Asymptotic-gain feedback model
The asymptotic-gain feedback model provides a solid base for relating controller imperfections such as:
Static (DC) gain limitation
Bandwidth limitation
Weak nonlinearity (differential gain)
to important performance limitations of the amplifier:
Gain inaccuracy
Frequency response
Differential gain
Presentation
The presentation Asymptotic-gain model introduces the asymptotic-gain feedback model.
Video
Asymptotic-gain feedback model
Study
Chapter 10.3.1, 10.3.2
Selection of the loop gain reference variable
The analysis of feedback circuits with the asymptotic-gain feedback model gives the same result as network analysis techniques. However, if the loop gain reference is selected in a proper way, the asymptotic-gain model provides much more design information and it facilitates two-step design of negative feedback circuits.
Presentation
The presentation Selection of the loop gain reference illustrates the way in wich the loop gain reference should be selected such that the model provides meaningful design information.
Presentation in parts
Selection of the loop gain reference (parts)
Videos
Downloads
SLiCAP_python source files Chapter 10
Study
Chapter 10.3.3, 10.3.4
Port of impedance single-loop feedback amplifiers
The port impedance of single-loop feedback amplifiers can be expresses in terms of the asymptotic-gain feedback model.
Presentation
The presentation Port impedance of single-loop feedback amplifiers shows the way in which this can be done.
Presentation in parts
Port impedance of single-loop feedback amplifiers (parts)
Video
Port impedance of single-loop feedback amplifiers.
Study
Chapter 10.3.6