The document provides an overview of active filters, which are analog circuits that utilize active components like amplifiers to implement frequency selective filtering. It classifies active filters into four types: low pass, high pass, band pass, and band stop, detailing their functions, configurations, and frequency responses. The document also discusses the merits and demerits of active filters, including their flexibility and performance benefits, while highlighting their limitations in cost, power handling, and frequency range.

1. Presented By: Group 3
Ipsita Raha – Dibyendu Banik – Arijit Dhali
11500120054 – 11500320062 – 11500320078
Active
Filters

2. Table of contents
02
01
04
Overview of Active Filter
& its Types
Introduction
Configuration &
Merits – Demirits
03
Conclusion
& References

3. Introduction
An active filter is a type of analog circuit implementing an electronic
filter using active components, typically an amplifier. Amplifiers included in a
filter design can be used to improve the cost, performance and predictability
of a filter.

4. What is a Filter?
A filter is basically a “ frequency selective “ circuit. It is
designed to pass a specific band of frequencies and
block input signals of frequencies outside this band.
Classification of Filters:

5. Active filters are the electronic circuits, which consist of
active element like op-amp(s) along with passive elements
like resistor(s) and capacitor(s).
Active filters are mainly classified into the following 4 types based on
the band of frequencies that they are allowing and / or rejecting −
● Active Low Pass Filter
● Active High Pass Filter
● Active Band Pass Filter
● Active Band Stop Filter
What is Active Filter?

6. Active Low Pass Filter
This filter designed to pass all frequencies
below a given cut-off frequency
Cut-off Frequency : Fc =
1
2𝜋𝑅𝐶
Phase Shift : 𝜑 = −45°

7. o It shows that a low pass filter has a constant gain from 0 to
a high cut off frequency fc.
o The frequencies between 0 to fc are known as “ passband
frequencies” whereas the frequencies beyond fc are
known as the “stopband frequencies”.
o At f= fc the filter gain makes a sudden transition to zero.
Therefore all the frequencies beyond fc are completely
attenuated.
o This figure shows the frequency response of a practical
low-pass filter. gain does not change suddenly at f= fc.
Instead as f increase, the gain reduces gradually.
Configuration of Active Low Pass Filter
Frequency Response of
Low Pass Filter

8. Active High Pass Filter
This filter designed to pass all frequencies
above a given cut-off frequency.
Cut-off Frequency : Fc =
1
2𝜋𝑅𝐶
Phase Shift : 𝜑 = +45°

9. o Its “stopband” extends from f=0 to f=fc where fc is the cut
off frequency. the “passband” will be for all frequencies
above Fc.
o The gain of an ideal high-pass filter is 0 over its stopband
constant over its passband.
o The gain make a sudden transition from 0 to 1 at f= fc
Configuration of Active High Pass Filter
Frequency Response of
High Pass Filter

10. Active Band Pass Filter
This filter is designed to pass all frequencies that fall
between its cut-off frequencies(FC1 and FC2)
Center Frequency : Fr = 𝐹𝐿 ∗ 𝐹𝐻
Phase Shift : 𝜑 = 180°

11. o Its “passband” extends between the two cut-off
frequencies fL anfd fH with fH>fL. The frequencies outside
this passband lie in the “stopband “.
o The gain of an ideal bandpass filter is 0 over the stopband
and constant over its passband.
o The gain will make sudden trasitions from 0 to 1 at f=fL and
from 1 to 0 f=fJ
Configuration of Active Band Pass Filter
Frequency Response of
Band Pass Filter

12. Active Band Stop Filter
This filter in designed to block all frequencies that fall
between its cut-off frequencies(FC1 and FC2)
Center Frequency : Fc = 𝐹𝐿 ∗ 𝐹𝐻
Phase Shift : 𝜑 = 180°

13. o The transformation of this filter characteristic can be
easily implemented using a single low pass and high
pass filter circuits isolated from each other by non-
inverting voltage follower, (Av = 1).
o The output from these two filter circuits is then summed
using a third operational amplifier connected as a
voltage summer (adder)
Configuration of Active Band Stop Filter
Frequency Response of
Band Stop Filter

14. Merits & Demerits
Merits
o Flexibility in gain
o No loading problem
o No insertion
o Passband gain
o Small component size
o Use of the inductors can be avoided
o Control impedance
Demerits
o Costs more than Passive Filter
o Its has need dc supply.
o Active filter are limited in their
frequency range .op-amp had a finite
gain bandwidth product.
o Active filters can not handle of large
amount of power.

15. Active filters are used in communication systems for suppressing noise, to isolate a
communication of signal from various channels to improve the unique message signal
from a modulated signal.
These filters are used in instrumentation systems by the designers to choose a required
frequency apparatus and detach unwanted ones.
These filters can be used to limit the analog signal’s bandwidth before altering them to
digital signals.
Conclusion

16. • https://www.tutorialspoint.com/linear_integrated_circuits_applications/linear_integrated_circuits_applica
tions_active_filters.htm
• https://www.slideshare.net/Bangulkhanbaloch/active-filter-138582261
• https://www.slideshare.net/RajputManthan/active-filter
• https://www.electronics-tutorials.ws/filter/band-stop-filter.html
• https://www.electronics-tutorials.ws/filter/filter_6.html
• https://www.electronics-tutorials.ws/filter/filter_7.html
• https://www.electronics-tutorials.ws/filter/filter_5.html
Reference

17. For your precious attention
towards our presentation
Thank
You