What is a Band Pass Filter?
Solution: A Band Pass filter is a filter that passes frequencies in a desired range and attenuates frequencies below and above. A closely related Knowledgebase item discusses the concept of the Q of a filter. The Knowledgebase makes a distinction between high Q band pass filters and low Q bandpass filters. While there are separate terms for the opposite of a bandpass filter – the notch and band reject – there are no corresponding terms to differentiate between a high Q bandpass filter – covered by this item – and a low Q bandpass filter. This knowledgebase item is geared towards the single tone, narrowband RF, and IF type of filters. The audio, speech, and broadband communications type of filter are covered in the low Q bandpass filter item. The amplitude response of a band pass filter is flat from the center frequency down and up to points where it begins to roll off. The standard reference points for these roll-offs are the points where the amplitude has decreased by 3 dB, to 70.7% o
