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What is the difference between active filter and passive filter applications?

Electronic filters are circuits which perform signal processing functions, specifically to remove unwanted frequency components from the signal, to enhance wanted ones or both.
Passive filters contain passive components (R,L,C), they do not depend upon an external power supply and/or they do not contain active components such as transistors or battery. The simplest passive filters, RC and RL filters, include only one reactive element, except HYBRIED LC Filter which is characterized by inductance and capacitance integrated in one element.
Active filters are implemented using a combination of passive and active (amplifying) components, and require an outside power source. operational filters are frequently used in active filter designs. These can have high Q Factor, and can achieve resonance without the use of inductors. However, their upper frequency limit is limited by the bandwidth of the amplifiers. The most common types of active filters are classified into four such as 1.Butterworth 2.Chebyshev 3.Bessel 4.Elliptical
The difference between Active and Passive Filters
1. Passive filters consume the energy of the signal, but no power gain is available; while active filters have a power gain.
2. Active filters require an external power supply, while passive filters operate only on the signal input.
3. Only passive filters use inductors.
4. Only active filters use elements kike op-amps and transistors, which are active elements.
5. Theoretically, passive filters have no frequency limitations while, active filters have limitations due to active elements.
6. Passive filters have a better stability and can withstand large currents.
7. Passive filters are relatively cheaper than active filters.
Applications of Active filters
  • Active filters are used in communication system 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 signals bandwidth before altering them to digital signals.
  • audio systems by engineers to send various frequencies to various speakers. For example, in the music industry, record & playback applications are needed to control the frequency components.
  • Active filters are used in biomedical instruments to interface psychological Sensors with diagnostic equipments & data logging.
Applications of Passive filters
  • low pass filters Woofers for low frequency, and Tweeters for high frequency reproduction). In this application the combination of high and low pass filters is called a "crossover filter".
  • high pass filters especially audio amplifiers
  • band pass filters while rejecting signals at all frequencies above and below this band
  • band stop filters older radio and TV receivers
  • I.F Transformers found in older in radio and TV equipment to pass a band of radio frequencies from one stage of the intermediate frequency (IF) amplifiers.

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