# When negative voltage feedback is applied to an amplifier of gain 150, the overall gain falls to 15. Find the fraction of the output that is feedback to the input.

$(a)\;1.06 \\ (b)\;0.06 \\ (c)\;0.01 \\ (d)\;0.03$

$A= 150$
$A_f =15$
$A_f= \large\frac{A}{1+\beta A}$
$15 =\large\frac{150}{1+150 \beta}$
$15 +2250 \beta =150$
$2250 \beta =150-15$
$\qquad=135$
$\beta= \large\frac{135}{2250}$
$\qquad= 0.06$
answered Jan 28, 2014 by
edited Jul 14, 2014