The band rejection filter circuit is not wide filter that can denial the frequency up to 60dB by we used the TL071 single chip op-amp it is very low distortion and work good at output to maximum to 100kHz or the range 1Hz to 20kHz. In the circuit we defined three resistors R1,R2,R3 are like value to 100K, and then two capacitors C1,C2 are equal to 330pF, For will reject the frequency at 50Hz.
By we can select the parts with the formula is F = 2×3.14xRC , And to get rejection well than 40dB if we should the resistor matched to 0.1% and capacitor to 1%.
The circuit is the right narrow filter for well audio system, we hope you enjoy with this circuit ideas.
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