buddypoor
|
Although Tosei gave already a comprehensive and complete answer, here is a short practical view:
All formulas to be used for gain, input/output impedances, ..... are based on the assumption that the system is linear (resp. linearized in a certain bias point). Example: A PLL is a highly non-linear system. However, for PLL design it is important and neccesary to use a linearized (that means: idealized) system. Only in this case the knowledge and all the rules of the linear control theory (loop gain, stabilty,....) are applicable.
|