Question
What is the frequency above which a low-pass filter’s output power is less than half the input power?
Answer Options
- A) Notch frequency
- B) Neper frequency
- C) Cutoff frequency
- D) Rolloff frequency
Correct Answer: C
Explanation
A low-pass filter (LPF) is designed to pass frequencies below a certain point and block (attenuate) frequencies above it. The point that marks the transition from passing to blocking is a critical metric.
This specific transition point is called the cutoff frequency (f_c). By definition, the cutoff frequency is the frequency at which the output power has dropped to exactly half of the input power (which is a reduction of approximately 3 \text{ dB}). This is also known as the 3 \text{ dB} down point, and it defines the functional limit of the filter’s passband.
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