| 摘要 |
PROBLEM TO BE SOLVED: To make the phase locked loop more stably by automatically matching a self-oscillating frequency of a voltage controlled oscillator of the phase locked loop with an object frequency without external adjustment. SOLUTION: The phase locked loop is made up of a phase detector 10, a 1st low pass filter 20, a 2nd low pass filter 60, a 3rd low pass filter 80, an amplifier 90, a voltage/current converter 70 receiving an output voltage from the 2nd low pass filter and converting the voltage into a current and providing an output of it, a DC level introduction device 100 receiving an output of the amplifier 90 and a buffer enable signal (BUF- EN) and providing an output of a voltage selection signal and a voltage controlled oscillator voltage, a switch means 50 and a voltage controlled oscillator 40. In this case, the oscillated frequency is automatically restored to a prescribed self-running oscillating frequency by varying the control DC voltage in a direction of cancelling parameter changes such as static capacitance. |
