Passive Filter: It does not contain any "active components", such as transistors, capable of increasing the signal level of the filter output. They use only what are called "passive components" such as resistors, capacitors, and inductors. Passive filters are circuit sub units often consisting of only two or three components, which reduce (ATTENUATE) the amplitude of signals, They are designed to be frequency selective so that they can reduce the signal amplitude at some frequencies, but do not affect signals at others. The block diagrams indicate the frequency that is attenuated by showing three sine waves with one or two crossed out, the vertical position of the wave indicating high medium or low frequencies.
Active Filters: An active filter is a type of analog electronic filter that uses active components such as an amplifier. Amplifiers included in a filter design can be used to improve the performance and predictability of a filter, while avoiding the need for inductors (which are typically expensive compared to other components). They draw their power from an external power source and use it to boost or amplify the output signal.