FM_SCANNER_NOISE_SQUELCH

Published:2009/6/23 4:37:00 Author:Jessie | From:SeekIC

The LM389 is operated in the cut-off mode with pin 12 grounded via one of the internal transistors. A sample of detected noise is taken through a 5-kHz filter. Upon reception of signal, the detec-tor output quiets, and noise level drops. This increases impedance at pin 12 of the LM389, causing audio to be passed. The three transistors are part of the LM389.



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