What is Active Band Pass Filter


An active band pass filter is an electronic circuit that allows a specific range of frequencies to pass through while attenuating frequencies outside the range. The filter achieves this by using an active component such as an operational amplifier (op-amp) in combination with passive components such as resistors and capacitors. The active band pass filter finds application in various electronic circuits such as audio signal processing, radio communication systems, and instrumentation.

Characteristics of Active Band Pass Filter

  • Allows a specific band of frequencies to pass through while attenuating frequencies outside that band.
  • The center frequency and bandwidth can be adjusted by changing the values of the components or through active components such as op-amps.
  • Provides gain or amplification to the filtered signal.
  • Has a low output impedance.
  • Has a flat response within the passband and a roll-off response outside the passband.
  • Used in audio equalizers, tone controls, and signal processing circuits.


The active band pass filter circuit consists of an op-amp, two feedback resistors, and two capacitors. The op-amp is configured in a non-inverting or inverting amplifier mode, and the feedback resistors and capacitors are connected in a band-pass filter configuration between the op-amp input and output. The input signal is applied to the inverting or non-inverting input of the op-amp, and the output signal is taken from the op-amp output.


In an active band pass filter, the two capacitors act as frequency-dependent impedances that form a band-pass filter. The two feedback resistors set the gain and Q-factor of the filter. The op-amp provides gain to the input signal and compensates for the signal loss due to the filter. The frequency range that the filter allows to pass through is determined by the values of the two capacitors and the two feedback resistors.


Some of the applications of active band pass filters are:

  • Audio signal processing in music systems and amplifiers
  • Radio communication systems for frequency filtering
  • Instrumentation and measurement systems
  • Seismic data acquisition and filtering
  • Ultrasonic signal processing and filtering

Leave a Comment