Answer1

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WHAT'S YOUR ENGINEERING QUOTIENT?

Problem 5—The value of R in the oscillator circuit shown below is chosen so that it just oscillates at an angular frequency of w. Calculate the value of R and w.

Answer 5

The angular frequency is:

w = 1
sqrt(LC) = 1
sqrt(10E-3 � 0.01E-6) = 10⁵ rad/sec

For oscillation, loop gain AB must be 1. In the above circuit, the forward gain A is 1 + 500K/5K = 101. The feedback factor B is 1K/(1K + R).

AB = 101 � 1K/(1K + R) = 1

Solving the above equation for R, we get R = 100 kohm.

Contributor: Naveen PN

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