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Active filter vs Passive filter-difference between active filter and passive filter

This page compares Active filter vs Passive filter and mentions difference between Active filter and Passive filter types. Advantages and disadvantages of both active filter and passive filter are also compared.

Filter definition:
The filter is a circuit which changes amplitude and phase of the input signal and produces output accordingly. It filters or eliminates some frequencies and passes some frequencies. Hence it provides different attenuations to different frequencies. Based on components used in the construction of the filter there are two types of filters viz. active filter and passive filter.

Active filter

First Order All-Pass Filter

Active Filter:
This filter type uses active components such as OP-AMP (i.e. operational amplifier) in addition to Resistors (R) and Capacitors (C) in the construction of the filter. Hence it is known as active filter. First order all pass active filter is depicted in the figure-1.

• No resonance issue
• It can eliminate any harmonics
• Used for voltage regulation
• Used for reactive power compensation
• It provides reliable operation

• It is expensive
• It provides complex control systems.

Passive Filter

rf filter design fig2

Passive Filter:
This filter type uses passive components such as resistors (R), coils or inductors (L) and capacitors (C) in the construction of filter. Hence it is known as passive filter. Normalized passive filter of order five and Lowpass type is depicted in the figure-2.

• Cheap
• Reliable
• Easy design
• High efficiency

• Resonance problems
• Tuning for fixed frequency
• Fixed reactive power compensation
• Large size

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