Question

In a series resonance type BPF, C = 1.8 pf, L = 25 mH, RF = 52 Ω and RL = 9 kΩ. The Bandwidth is ___________

(a) 331 kHz

(b) 575 kHz

(c) 331 Hz

(d) 575 Hz

The question was posed to me during an interview.

The origin of the question is Problems of Series Resonance Involving Quality Factor in section Resonance & Magnetically Coupled Circuit of Network Theory

Answer 1

Correct option is (c) 331 Hz

To elaborate: R = \(\frac{R_f×R_L}{R_f+R_L}\) ≈ 52 Ω

∴ Qfactor = \(\frac{ω_r L}{R} = \frac{2π×751×25×10^{-3}}{52} \)

= \(\frac{π×37580}{52}\) = 2270

Now, BW = \(\frac{f_r}{Q} = \frac{751 × 10^3}{2270}\)

∴ BW = 331 Hz.