| 摘要 |
PURPOSE:To improve a followability by connecting the output edge of a current output type operational amplifier to the output side of a phase comparator, switching the condition of the operational amplifier and supplying a variable voltage. CONSTITUTION:At an ordinary action time, the gain of an operational amplifier 5 goes to '0', and the output of a charging pump type phase comparison is separated and stably operated. At the time of inputting a supply voltage and at the time of a variable speed reproduction, a switching circuit 21 is turned on, the gain of the operational amplifier 5 is a prescribed value and the output is supplied to a capacitor 4. For this reason, the voltage of the capacitor 4 is forcibly pulled in so as to be equal to the voltage of the variable voltage 10, and rapidly, the center of the oscillation frequency of a VCO 8 is set to the prescribed value. Further, when a dummy lock occurs, a switching circuit 20 is turned on, and the gain of the operational amplifier goes to a prescribed value. The voltage is more strongly and forcibly pulled in than the above- mentioned case. |
