| 摘要 |
PURPOSE: To shorten the convergence time of a control cycle without being almost affected by an attenuation phenomenon by comparing the frequency of a frequency division signal with reference frequency by a 2nd comparator when both frequency bands are different far from each other. CONSTITUTION: This video frequency tuner circuit 1 including a voltage controlled oscillator 3, a frequency divider 4, a phase comparator 5, and a low-pass filter(LPF) 6 is provided with the 2nd comparator 10 connected between the output of the divider 4 and the LPF 6 in parallel with the comparator 5. When signal frequency outputted from the divider 4 is different far from the reference frequency, both frequency bands are compared with each other by the 2nd comparator. Consequently a highly efficient control cycle can be applied to the tuning of video frequency for extremely a short holding time and the convergent time of tuning can be shortened. |
