Question

Which of these is incorrect for a band-stop filter?

(a) An adder is required when designing it using LPF and HPF

(b) LPF and HPF are connected in parallel

(c) The HPF cut-off frequency should be much higher than LPF cut-off frequency

(d) The LPF and HPF are connected in series

This question was addressed to me in an interview for job.

Asked question is from Frequency Filters in portion Op-amps and its Applications of Analog Circuits

Answer 1

Correct choice is (d) The LPF and HPF are connected in series

The explanation: When designing a band-stop filter, a HPF and LPF are connected in parallel, and their output goes into the input of an adder to get the desired output. For correct output, the cut-off frequency of HPF should be much higher than that of the LPF.