Discussion of the exercises from previous days
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Derive controller requirements from amplifier requirements
Bandwidth of a negative feedback amplifier
For design purposes it is convenient to decouple the definition of the bandwitdth of a negative feedback amplifier from its desired frequency characteristic. This can be achieved by defining the bandwidth of a negative feedback amplifier by that of its servo function.
Presentation
The presentation “Bandwidth of a negative feedback amplifier shows that the bandwidth of a negative feedback amplifier will be defined as that of its servo function.
Video
Bandwidth definition for negative feedback amplifiers (3:40)
Study
Chapter 11.4.1
Example: Bandwidth of a negative feedback transimpedance integrator
Presentation
The presentation “Bandwidth Transimpedance Integrator shows the bandwidth definition for a negative feedback transimpedance integrator.
Video
Example Bandwidth definition for an OpAmp Integrator Circuit (7:12)
study
Chapter 11.4
Butterworth or Maximally Flat Magnitude (MFM) responses
The -3dB cut-off frequency of systems with a Butterworth or MFM transfer equals the Nth root of the magnitude of the product of their N poles, where N is the order of the system.
In this course we will design the frequency response of a feedback amplifier in such a way that the servo function obtains an MFM or Butterworth filter characteristic over the frequency range of interest. Design procudures for other filter characteristics, such as, Bessel or Chebyshev do not differ. Only the numeric relation between the -3dB bandwidth and the gain-poles product of the loop gain will be different.
Presentation
The presentation “Butterworth or Maximally Flat Magnitude (MFM) responses shows the Laplace transfer functions, the pole patterns and the magnitude characteristics of first, second and third order Butterworth transfers.
Video
Butterworth frequency responses (4:07)
Study
Chapter 11.4.3
MFM bandwidth of an all-pole feedback amplifier
The product of the loop gain and the magnitude of the dominant poles of the loop gain is a design parameter for the -3dB MFM bandwidth of an all-pole negative feedback amplifier .
Presentation
The presentation “All-pole loop gain and servo bandwidth proofs the above.
Video
All-pole Loop Gain and Servo Bandwidth (5:13)
Study
Chapter 11.4.3
Determination of the dominant poles of the loop gain
Presentation
The presentation “Dominant and non-dominant poles in feedback systems illustrates the procedure for separating dominant poles and non-dominant poles on feedback systems.
Video
Dominant poles and non-dominant poles of the loop gain (8:53)
Study
Chapter 11.4.3
Determination of the requirement for the gain-bandwidth product of an operational amplifier
The requirement for the GB-product of an operational amplifier can be derived from the loop gain-poles product (for dominant poles only).
Presentation
The presentation “Determination of OpAmp GB-product requirement illustrates the procedure for deriving the requirement for the gain-bandwidth product of the operational amplifier from the expression of the loop gain.
Video
Determination of GB product requirements for operational amplifiers (5:35)
Study
Chapter 11.4.3
Frequency stability of negative feedback systems
A system is stable if its responses to bounded excitations are also bounded.
A lumped system is said to be stable if the solutions of its characteristic equation (the poles) all have a negative real part.
Presentation
The presentation “Frequency stability of feedback amplifiers presents three ways to determine the stability of feedback systems.
Study
Chapter 11.5
Guidance with homework
The theory presented in day 6 will be applied in the design of the active antenna. Please use SLiCAP as documentation tool.
