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Hum Filter (741) Circuit

2017-02-26 10:30  
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Hum Filter (741) Circuit
The Hum Filter Circuit is showed in the picture. The circuit is an economical narrow-band notch filter. It does not need elements of high accuracy. The frequency can be changed from 50Hz to 60Hz. It is used to eliminate the useless signal and hum in the audio and test instrumentation system. Differential feedback overhead active RC network is used in the circuit. The Notch Bandwidth depends on the feedback value. The Notch Bandwidth is narrow when the feedback value is high. Use the element value in the picture to adjust the potentiometer. It can adjust the frequency to 50Hz or 60Hz. The suppression of hum can reach the value of 30dB. When the frequency is 50Hz the bandwidth is 14Hz. When the frequency is 60Hz the bandwidth is 18Hz. The attenuation of signal is less than 1dB.