Language filter circuit designed by LM387

Language filter circuit

This circuit can be used to limit the speech frequency band and remove interference and noise other than speech. This function is achieved by using two multi-channel negative packet-fed second-order active filters. The two-stage filters are cascaded. The front stage is a high-pass filter, the rear stage is a low-pass filter, and the overall characteristic is a band-pass filter. The high-pass cutoff frequency is 300HZ, forming the low end of the band-pass filter, while the low-pass cutoff frequency is 3000HZ, forming the band. Pass the high end of the filter. The out-of-band rolling attenuation is 40dB per decade, and the overall circuit gain is 1.