Question

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(5) 20pts) An op-amp configuration show below, please figure out the fp find the feedback factor (a) Assume the op amp has infinite input resistance and zero output resistance, B; b) If A-4 10, find the Ac c) What is the amount of feedback in decibels? e) If FL-S He and FH-90 MHa, find Fy and Fu D V-2(),find Va Vand V R, o V. Ne Ri+ R Ri VE

Answer 1

The feed back network is this is feedback to the op- amp therefore v_f = v_0 times R_1/R_1 times R_f therefore beta = v_f/v_0 = R_1/R_1 + R_f for a negative feedback network. The overall gain A_f = A/1 + A beta implies where A = 4 times 10^4 therefore Af = 4 times 10^4/1 + 4 times 10^4 times f_1/R_1 + R_f feed back in decibels = 20 log B 20 log R_1/R_1 + R_f given Vertical-bar delta A/A Vertical-bar = 20 percent A_f = A/1 + A beta, Af = delta A (1 + a beta) - (beta) A/(1 + A beta)^2 = d A_f/da therefore nabla A_f = d A_f/D_A = delta a/(1 + A beta)^2 nable A_f/A_f = delta a/A(1 + A beta) Vertical-bar delta A/A Vertical-bar /(1 + a beta) implies 20 %/1 + A beta = 20 %/1 + 4 times 10^4 times R_1/R_L + R_f R_L & R_f values are not provided \r\n f_L = 9khz & F_H =