Compared to a simple RC filter, a resonant LC band-pass filter offers which combination of Q, selectivity, and insertion loss?

Compared to a simple RC filter, a resonant LC band-pass filter offers which combination of Q, selectivity, and insertion loss?

• A. Higher Q, sharper selectivity; lower insertion loss
• B. Lower Q, broader selectivity; higher insertion loss
• C. Higher Q, broader selectivity; higher insertion loss
• D. Lower Q, sharper selectivity; lower insertion loss

Answer: (A)

The key idea is that resonance in an LC tank boosts selectivity by creating a very sharp passband, which is captured by a high Q. A simple RC filter isn’t a resonant circuit, so its response is broad and lacks a well-defined, narrow peak; its energy is dissipated mainly through the resistor, giving modest selectivity and a relatively higher insertion loss in comparison to a tuned network. An LC band-pass, when tuned to a center frequency, presents minimal impedance (or maximum impedance, depending on configuration) right at that frequency, allowing energy to pass with little loss while rejecting frequencies away from center. The result is a much higher Q and much sharper selectivity. If you use high-quality, low-loss inductors and capacitors, the energy stored in the tank can circulate with minimal dissipation, so the insertion loss in the passband is lower than in a simple RC filter. So, compared to a simple RC filter, a resonant LC band-pass filter delivers higher Q, sharper selectivity, and lower insertion loss.

The key idea is that resonance in an LC tank boosts selectivity by creating a very sharp passband, which is captured by a high Q. A simple RC filter isn’t a resonant circuit, so its response is broad and lacks a well-defined, narrow peak; its energy is dissipated mainly through the resistor, giving modest selectivity and a relatively higher insertion loss in comparison to a tuned network. An LC band-pass, when tuned to a center frequency, presents minimal impedance (or maximum impedance, depending on configuration) right at that frequency, allowing energy to pass with little loss while rejecting frequencies away from center. The result is a much higher Q and much sharper selectivity. If you use high-quality, low-loss inductors and capacitors, the energy stored in the tank can circulate with minimal dissipation, so the insertion loss in the passband is lower than in a simple RC filter. So, compared to a simple RC filter, a resonant LC band-pass filter delivers higher Q, sharper selectivity, and lower insertion loss.