| 摘要 |
<p>In an FM demodulator of the phase locked loop system wherein a closed loop is formed by a phase detector (2), an amplifier (3'). a loop filter (4), and a voltage controlled oscillator (5), a part of the amplifier (3') is formed by a differential amplifying circuit (14) which has a constant current source (13) and is driven by a constant current. The center frequency of the frequency demodulation slope of the constant current source (13) is changed by changing the current from the constant current source in response to the signal which was frequency demodulated by the phase locked loop. Further, a low-pass filter (17; 30) having the pass band of the frequency band of the signal to be modulated is provided in the path of the system from the differential amplifying circuit (14) to the constant current source (13).</p> |
