What is the significance of unilateral in Feedback concepts?

[iVenky]

I was studying about feedback. The book says it is necessary to assume that the basic amplifier is unilateral. What will happen if the amplifier ( a negative feedback) is not unilateral?


Note: I know the meaning of "unilateral" (which I believe is " The output resistance doesn't depend upon the source resistance and similarly the input resistance does not depend upon the load resistance).

 

[erikl]

I think "unilateral" means the signal flow is "unidirectional" (one way only), i.e. there's no (negative or positive) feedback inside the involved gain stage itself. Feedback elements are only outside of that gain stage.