Phase locked loop stabilized against temperature and voltage variations

摘要

A phase-locked loop circuit uses a voltage control oscillator which varies its frequency in response to a certain control signal. A first logic circuit generates pulses having pulse widths that are proportional to the phase differences between applied input pulses and the pulses from the oscillator. The output of the first logic circuit is filtered. Second and third logic circuits are used for generating high and low d.c. levels, respectively. The output levels of the second and third logic circuits are combined into a predetermined synthesized d.c. level. The control signal is generated, corresponding to the level difference between the outputs of the filtering means and the synthesized d.c. level.