| 摘要 |
PURPOSE:To suppress generation of noise at no FM signal and a small level signal by providing two comparators each having a threshold voltage of different polarity. CONSTITUTION:An FM signal S0 from an input terminal 1 is branched into two; one is fed to a non-inverting terminal of the comparator 2 and the other is fed to an inverting terminal of the other comparator 3 respectively. On the other hand, a threshold voltage having different polarity is given respectively to the comparators 2 and 3. Then outputs S1', S2' of monostable multivibrators 4, 5 triggered by comparison outputs S1, S2 of the comparators 2, 3 are added (6). A sum signal S3 is given to an LPF7, where it is demodulated. Since the circuit is formed in this way, the comparators 2, 3 are not activated at no FM signal S0 or a signal of small level, then no demodulation signal S3 is outputted. Thus, generation of noise is suppressed. |
