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A system has a gain of 80 db without feedback, if the negative feedback is 1/50th. What is the closed loop gain of the system in db with the addition of the negative feedback?(a) 34db(b) 40db(c) 30db(d) 42dbThis question was posed to me in an online quiz.My enquiry is from Properties of Negative Feedback topic in portion Differential and Multistage Amplifiers of Electronic Devices & Circuits

Answer» CORRECT CHOICE is (a) 34db

To elaborate: 80db = 20log (G)

THEREFORE, G= antilog 10(80/20)

=10,000

Gv = G/ (1+GB)= 10,000/ (1+10,000/50)= 49.75

Gv (db) =20log (49.75) = 34db.


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