Question

For providing a Roll-off greater than 20dB/decade/pole, filters with which characteristics are useful?

(a) Butterworth

(b) Chebyshev

(c) Bessel

(d) Butterworth & Bessel

This question was addressed to me in an interview.

The origin of the question is Advanced Problems on Filters in division Filters and Attenuators of Network Theory

Answer 1

Correct option is (b) Chebyshev

For explanation I would say: Roll off is a term commonly refers to the steepness of the transmission function wrt to the frequency.

For a Chebyshev filter, the Roll-off value greater than 20. This characteristic feature is useful when a rapid roll-off is required because it provides a Roll-off rate of more than 20.

On the other hand, both Butterworth and Bessel have the Roll-off rate less than or equal to 20 dB/decade/pole.