Difference between active and passive filter

The filter is one type of circuit which changes amplitude and phase of the input signal and produces output. The filters eliminate some frequencies and pass some frequencies hence it provides different attenuation to different frequencies. Based on components used in the construction of the filter there are two types of filters one is active filter and other is a passive filter. 

What is an active filter? 

The active filter uses active components such as operational amplifier addition to resistors and capacitors in the construction of the filter. 

What is a passive filter? 

The passive filter uses passive components such as resistor, coils or inductors and condenser or capacitors in the construction of the filter. 

Active filters require an external power supply while we are using passive filter operate only on the signal input. Here this article gives information about the active filter vs passive filter to better understand this topic.

Main difference :

The main difference between active and passive filter is that passive filters can't cause a power gain or can't bring energy into circuit whereas active filter can add energy into the circuit and also control current. 

Difference :
  • The active filter requires an external power supply while passive filters operate only on the signal input.
  • A passive filter is constructed using only passive components while active filters may contain active as well as passive components.
  • The active filter uses elements like op-amps and transistor which are active filter elements.
  • Passive filters have no frequency limitations while active filters have a limitation due to active elements.
  • Only passive filters use inductors.
  • Passive filters consume the energy of the signal, but not power gain is available while active filters have a power gain.
  • Passive filter has no external power source, active filters require an external power source.
  • Passive filters are relatively cheaper than active filters.
  • The passive filter has better stability and can withstand large currents.
  • The passive filter may consist of inductors, active filter do not contain inductors.
  • Compared to active filters properties of passive filters may change significantly when the load it must be changed.
  • Passive filters can be used at high frequencies by using inductors, while in active filters the frequency range is dependent on the bandwidth of the amplifier typically to filter high-frequency signals, passive filters are used.