Oscillator frequency regulating circuit - varies frequency between given limits in accordance with external frequency supplied to phase comparator

摘要

The oscillator frequency-regulating circuit is used to vary the oscillator frequency between fixed lower and upper limits in accordance with an external frequency. The latter frequency and the oscillator frequency are supplied to a phase comparator (PVS), providing a DC voltage representing the frequency difference. The latter is supplied to the oscillator (VCO) via a low-pass filter for adjusting the oscillator frequency. If the voltage from the phase comparator (PVS) exceeds that corresp. to the max. or min. oscillator frequency, the latter is held at its max. or min.