# Question 03d44

Nov 22, 2017

The answer is selection: a) 5

#### Explanation:

The general equation for a positive feedback system is:

${A}_{\text{c" = A_"ol"/(1 - betaA_"ol")" [1]}}$

Where ${A}_{\text{c}}$ is the closed loop gain, ${A}_{\text{ol}}$ is open loop gain, and, $\beta$ is the gain of the feedback circuit.

We are given that ${A}_{\text{c}} = 10$

And the phrase; "10% positive feedback" implies that $\beta = 0.1$

Substitute these values into equation [1] and solve for ${A}_{\text{ol}}$:

10 = A_"ol"/(1- 0.1A_"ol")

10(1- 0.1A_"ol") = A_"ol"#

$10 - {A}_{\text{ol" = A_"ol}}$

$2 {A}_{\text{ol}} = 10$

${A}_{\text{ol}} = 5$

The answer is selection: a) 5