The working principle circuit diagram of HT9170

Published:2011/7/20 20:13:00 Author:Ecco | Keyword: working principle | From:SeekIC

HT9170 will send DTMF signal to the pre-filter (actually a band stop filter) after passing the operational amplifier to filter the 350 ~ 400Hz low frequency interference and noise in DTMF signals. Basically, the output signal contains only two frequencies. The output signals will output high-frequency and low-frequency sine wave signals after respectively passing the two band-pass filters with high-frequency and low-frequency filters, then they will be turned into the rectangular pulses with the same frequency after shaping by the Schmitt circuit.



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