Wiley signals and systems e book TLFe BO 411

16 Stabilitv avid Fkcdback Svsteins 396 Figure lfi.4: Structure of the system G ( s ) with ftdback loop S ~ ~the ~ t ~ i ~ ~ Wheii c ~ n ~ t i i i ~an t ,electronic ii~~ iiiiqAifier, for cxample, for audio usc, the principle o f riegativc feedbacl~> i1can he built eabily, it' strong variations in the freqiieiry rcsponse F ( j w ) can 1x2 tolcratcd Some of the amplification is t h w sacrificed, by conuectir-rgthc nirtpul Itack to the input with a gaiu fwtor K , The rcsinlt iiig freqixency respame is nearly constant It is important, of coiu'w, that J F ( j u ) is J large enough ihat the ineqiialit~y/ K F ( ~ J >> ) / is also true for small valixes of I