R. Mitchell (UK)
Feedback Systems, Bode diagrams, Asymptotic analysis.
In his classic book, Network Analysis and Feedback
Amplifier Design, Bode describes how to obtain using
asymptotic analysis, for a specified amount of bandwidth,
gain margin and phase margin, the `maximum obtainable
feedback'. This means, how to get the largest possible low
frequency loop gain for a single loop amplifier. One
problem with the method is that, particularly when
specifying too high a bandwidth, it is not possible to
achieve the specified phase margin, with the consequence
that the system step response can be too oscillatory. This
paper considers ways in which the phase margin can be
achieved, whilst still achieving the maximum obtainable
feedback over a large bandwidth.