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  • Category: Exam Questions

    Comparision of Active Filter and Passive filters

    What is Difference between Active Filter and Passive filters?
  • #62774
    passive filters are the combination of those components which do not require any external power supply such as resistors inductor and capacitors,on contrary active filters are the combination of active and passive elements like transistor

  • #62793

    Active Filter :
    Active Filter

  • These Make use of the active device and resistor and capacitor. No inductor is used.
  • As no inductor is used, circuit becomes compact and less in weight even at low frequencies.
  • It require dual power supply.
  • Input impedance is high.
  • As the output impedance is low, it can drive the low impedance load.
  • Load is isolated from the frequency determine network. So variation in load does not affect the characteristic of the filter.
  • It is possible to increase the gain.
  • Parameters like gain, pass band, cut off frequency can be adjusted.
  • High frequency response is limited by gain band width product and slew rate.
  • Variation in power supply voltage affects the output voltage.
  • Feedback through common supply rail may cause oscillations.

    Passive Filter :
    Active Filter

  • These make use of the passive components like inductor, capacitor, resistor etc.
  • Circuit becomes bulky and costly especially for low frequency because size of the inductor increases at lower frequency.
  • It does not need power supply.
  • Input impedance is less which loads the source.
  • Output impedance is more so it can not drive the low impedance load.
  • Load is not isolated from the frequency determining network so variation in load may affects the characteristic of filter.
  • It is not possible to increase the gain.
  • It is not possible to adjust the parameters.
  • No restriction at high frequency.
  • No power supply is used. So output us not affected.
  • No such problem arises.

    With best regards,


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