What are active filters? State its advantages over passive filters.
1 Answer


  • A filter is basically $a^{\prime \prime}$ frequency selective "circuit. It is designed to parse a specific band of frequencies and block or attenuate input signals of frequencies outside this band.

The active fillers use active devices such as op-AMp or transistors along with the passive components.

Active filters have more sharp frequency response characteristics.

Advantages of active filters:

1. Flexibility in gain and frequency adjustment:

  • In passive filters, the input signal is attenuated while passing through the filter.

  • But, in active filters, as an op-AMp can provide a gain, the input signal is not attenuated.

  • In addition, the active filter is easy to tune, therefore easy frequency adjustment is possible.

2. No loading problem:

  • The op-AMP has a high input resistance and low output resistance.

  • Therefore active filters using op -AMP do not load the input source or load.

3. Low cost;

  • Due to the easy availability of a variety of cheaper OP-AMPs and the absence of inductors in the active filters, the active filters are more economical than the passive filters.

  • The active fillers are used in almost all fields of Electronics such as communication, signal processing, radiotelephone, radar, space satellites, and biomedical equipment.

4. No insertion loss:

  • The active filters do not exhibit any insertion loss. Whereas the passive filters always show some loss of signal in their passband.

5. Passband gain:

  • The Active filter can be designed to provide some passant gain. This is not possible for the passive filters.

6. Interstage isolation and control of impedance:

  • Active filters also allow interstage isolation and input and output impedance control.

7. small component size:

  • The components required for the active filters are of smaller size as compared to those used for the passive filters.

8. Use of inductors can be avoided:

  • It is possible to avoid the use of inductors in complex active filters. This reduces the size of the fillers to a great extent.
  1. Using the active filler, the rapid design of stable economical fillers is possible.
Please log in to add an answer.