band pass filter

A bandpass filter passes a band, however attenuates the frequency ying beyond the band. Now, fo = Centre Frequency Ao = Mid band Gain B.W. = Band Width Q= Quality Factor = fo/B.W. The response of narrow band circuit is similar to that obtained with a simple series or parallel resonant circuit having a moderate Q. For this sitution the lower 3 dB frequency f1 & f2 respectively are quite close so that centre frequency is fo = under root(f1f2) and bandwidth, f1 - f2 = fo/Q. Calculations: f1 = 25 kHz & f2 = 400 Hz thus, fo = under root(f1f2) = 3.162 kHz Band width = f1-f2 = 24.6 kHz