Audio Rejection filter Circuit

This narrow band filter using the 741 operational amplifier can provide up to 60 dB of rejection. With resistors equal to 100 K and capacitors equal to 320 pF, the circuit will reject 50 Hz. Frequencies within the range 1 Hz to 10 kHz may be rejected by selecting components in accordance with the formula. To obtain rejections better than 40 dB, resistors should be matched to 0% and capacitors to 1%.

 Audio Rejection filter Circuit Diagram