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Placing Poles and Zeroes
(pt3: How and why to use gain and/or phase margin(s) as tools...)



As we've seen, to insure closed-loop stability when we "close the feedback loop", we would like to have an open-loop system for which we have: ...and we would (in general) like to AVOID The past few pages have shown how adjusting a constant gain times a transfer function: We can therefore sometimes* adjust a constant GAIN value times an open-loop system, which will in turn create systems which are either stable or unstable when we close the loop.

(*Of course, some open-loop systems may remain solely unstable or solely stable for all gains values we might choose...)
gonzo@mit.edu 2.010 Tutorial #3, 29-Sep-00