| 摘要 |
PROBLEM TO BE SOLVED: To provide a carrier-detecting circuit for smoothing an error signal from a phase comparator without using plural order RC filters, and obtaining the degrees of freedom of time setting. SOLUTION: This is a carrier-detecting circuit 30 for converting an error signal E1 outputted from the phase comparator of a PLL circuit constituting an FSK demodulator into a DC level, and comparing it with a reference value for detecting the presence or absence of an input signal to the FSK demodulator. The error signal E1 can be converted into the DC level by one capacitor C, constant current source 31 for always charging the capacitor C, and discharging circuit 32 for discharging the capacitor C when the error signal E1 is inverted. |
