If the bandstop filter in Fig. 14.37 is to reject a 200-Hz sinusoid while passing other frequencies, calculate the values of L and C. Take R = 150 Ω and the bandwidth as 100 Hz.

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Accepted Answer

We use the formulas for a series resonant circuit in Section 14.5.

B = 2π (100) = 200π rad/s

But

[latex] B = \frac{R}{L } ⇒ L = \frac{R}{B} = \frac{150}{200π} = 0.2387 H [/latex]

Rejection of the 200-Hz sinusoid means that [latex] f_{0} [/latex] is 200 Hz, so that [latex] ω_{0} [/latex] in Fig. 14.38 is

[latex] ω_{0} = 2π f_{0} = 2π (200) = 400 π [/latex]

Since [latex] ω_{0} = 1/ \sqrt{LC} , [/latex]

[latex] C = \frac{1}{ω^{2}_{0}L} = \frac{1}{(400π)^{2}(0.2387)} = 2.653 μF [/latex]

Chapter 14

Q. 14.11

Q. 14.11

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