In High Pass Filter we can get on the frequencies above the cut off frequency and in Low pass filter we get only the signals of frequencies below the cut off frequency. But if we required certain range of frequency only while the other frequencies are to be rejected, at that time there is requirement of a filter that allows only the band of frequency while the frequency lower than the range of frequency required and the frequencies above the range are not allowed to pass through the circuit.

A Band Pass Filters passes signals within a certain band of frequencies without distorting the input signal or introducing extra noise.

This band of frequencies can be any width and is commonly known as the filters Bandwidth.

Bandwidth is commonly defined as the frequency range that exists between two specified frequency cut-off points ( ƒc ),

So it can be said that the bandwidth is the difference between the lower cut-off frequency ( ƒcLOWER ) and the higher cut-off frequency ( ƒcHIGHER ) points. In other words, BW = ƒH – ƒL. Clearly for a pass band filter to function correctly, the cut-off frequency of the low pass filter must be higher than the cut-off frequency for the high pass filter.

The “ideal” Band Pass Filter can also be used to filter out certain frequencies that lie within a particular band of frequencies, for example, noise cancellation. Band pass filters are known generally as second-order filters, (two-pole) because they have “two” reactive component, the capacitors, within their circuit design. One capacitor in the low pass circuit and another capacitor in the high pass circuit.

The figure shows the ideal frequency response of the Band Pass Filter.

The figure shows the practical frequency response of the Band Pass Filter.