Control circuit for phase controlled oscillator - with pull-in range increased by positive and negative feedback with diode switching

摘要

The range of this control loop circuit for a phase controlled oscillator is increased by employing a combination of positive and negative feedback to an amplifier which produces a sawtooth waveform output for tuning the oscillator until it locks to a predetermined frequency. This circuit maintains a constant feedback current and eliminates the need for critical or frequency dependent feed back. The output voltage of an amplifier (3) is fed back to its inverting and its non-inverting inputs (12,11) via a capacitor (5) in a positive sense (5,6) and a negative sense (5,7,8) respectively. The negative feedback via diodes (7,8) comes into effect when these diodes conduct at a predetermined threshold voltage.