Active Low Pass Filters
The attenuation of the signal that is the amplitude of the output signal is lesser than amplitude of the input signal in the passive circuit. One way to overcome this disadvantage is to use amplification with the help of active filters. An active filter generally uses an operational amplifier (op-amp) within its design. They contain active components such as operational amplifiers or transistors, and draw their power from an external power source and use it to boost or amplify the output signal.
Active filters are generally much easier to design than passive filters, they produce good performance characteristics, very good accuracy with a steep roll-off and low noise when used with a good circuit design.
The most common and easily understood active filter is the active low pass filter. Its principle of operation and frequency response is exactly the same as those for the previously passive filter, the only difference is that it uses an op-amp for amplification and gain control. The simplest form of a low pass active filter is to connect an inverting or non-inverting amplifier.