# Linear Integrated Circuit Questions and Answers – Active Filters – 2

This set of Linear Integrated Circuit Multiple Choice Questions & Answers (MCQs) focuses on “Active Filters – 2”.

1. Which filter type is called a flat-flat filter?
a) Cauer filter
b) Butterworth filter
c) Chebyshev filter
d) Band-reject filter

Explanation: The key characteristic of the butterworth filter is that it has a flat pass band as well as stop band. So, it is sometimes called a flat-flat filter.

2. Which filter performs exactly the opposite to the band-pass filter?
a) Band-reject filter
b) Band-stop filter
c) Band-elimination filter
d) All of the mentioned

Explanation: A band reject is also called as band-stop and band-elimination filter. It performs exactly the opposite to band-pass because it has two pass bands: 0 < f < fL and f > fH.

3. Given the lower and higher cut-off frequency of a band-pass filter are 2.5kHz and 10kHz. Determine its bandwidth.
a) 750 Hz
b) 7500 Hz
c) 75000 Hz
d) None of the mentioned

Explanation: Bandwidth of a band-pass filter is Bandwidth= fH– fL=10kHz-2.5kHz=7.5kHz=7500Hz.

4. In which filter the output and input voltages are equal in amplitude for all frequencies?
a) All-pass filter
b) High pass filter
c) Low pass filter
d) All of the mentioned

Explanation: In all-pass filter, the output and input voltages are equal in amplitude for all frequencies. This filter passes all frequencies equally well and with phase shift and between the two function of frequency.

5. The gain of the first order low pass filter
a) Increases at the rate 20dB/decade
b) Increases at the rate 40dB/decade
c) Decreases at the rate 20dB/decade
d) Decreases at the rate 40dB/decade

Explanation: The rate at which the gain of the filter changes in the stop band is determined by the order of filter. So, for a low pass filter the gain decreases at the rate of 20dB/decade.
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6. Which among the following has the best stop band response?
a) Butterworth filter
b) Chebyshev filter
c) Cauer filter
d) All of the mentioned

Explanation: The cauer filter has a ripple pass band and a ripple stop band. So, generally cauer filter gives the best stop band response among the three.

7. Determine the order of filter used, when the gain increases at the rate of 60dB/decade on the stop band.
a) Second-order low pass filter
b) Third-order High pass filter
c) First-order low pass filter
d) None of the mentioned

Explanation: The gain increases for high pass filter. So, for a third order high pass filter the gain increases at the rate of 60dB/decade in the stop band until f=fL.

8. Name the filter that has two stop bands?
a) Band-pass filter
b) Low pass filter
c) High pass filter
d) Band-reject filter

Explanation: A band-pass filter has two stop bands: 1) 0 < f < fL and 2) f > fH.

9. The frequency response of the filter in the stop band.
i. Decreases with increase in frequency
ii. Increase with increase in frequency
iii. Decreases with decrease in frequency
iv. Increases with decrease in frequency
a) i and iv
b) ii and iii
c) i and ii
d) ii and iv

Explanation: The order of frequency of the filter in the stop band determines either steady decreases or increases or both with increase in frequency.

Sanfoundry Global Education & Learning Series – Linear Integrated Circuits.

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