| 摘要 |
<p>BPF having a band width of reference signal fREF - mixer output signal fMIX OUT is connected to a phase comparator. When an output signal corresponding to the passage of this band width has been obtained, a changeover switch is turned OFF. Upon detection such that the PLL circuit is unlockable, an output signal is obtained from an offset differential pair circuit, the changeover switch is turned ON, and the time constant of LPF is reduced to shorten the lock-up time, and the voltage applied to VCO is made larger than the usual voltage. By virtue of this construction, a PLL circuit of an analog system can be realized which can shorten the lock-up time and, in addition, can reduce noise and harmonic spurious. <IMAGE></p> |
