I have read that we need odd number of transistor stages to realize Y and Z feed backs and even number of transistor stages to realize H and G feedbacks can anyone explain me why this is the case?
In general to have a stable system you must have a negative feedback. If every stage give a 180 degree phase shift and all the stages are identical , you must have an odd number to have a negative feedback for stable system. you can have even number of stages if you have diffrential topology with cross coupled connection.
If your feedback is positive then unstability and osillations will happen which can be used for oscillators design not for amplifiers.
Mohamed Atef sir u mean is it the series series and shunt shunt topology in Y and Z feedbacks that contribute to the number of stages?
Hi Mr. M. Atef,
just one short supplement (correction?):
Negative feedback DECREASES dynamic stability - that means it can improve only DC stability against tolerance and temperature effects. It is a common misconception that negative feedback always improves stability in general. We clearly have to discriminate between dynamic and static stability.
Hi,MrLutz von Wangenheim.
sure, but i am here comparing negative and positive feedback.I am not comparing negative feedback to open loop system.
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