| 摘要 |
<p>The circuit can be used with a t.v. line sweep oscillator which is synchronised with an externally applied signal (2) and has a reference oscillator (14) operating at typically 4.43. MHz. The output is applied to one input of a comparator or coincidence detector (13) forming part of a phase locked loop with a second oscillator (11) whose output is applied to the comparator other input. A derivation circuit (15), such as a current reflector, obtains a current proportional to the comparator output current slaving the second oscillator to control a third oscillator (12) identical to the second oscillator. The third oscillator runs at 4MHz, the signal being divided by 256 to provide 15.625 KHz applied to the t.v. line sweep circuit, and has its phase and frequency regulated by a further coincidence circuit (5) comparing the external synchronising signal with the line sweep circuit signal. The captive range of the third oscillator is weak and the second coincidence circuit has a short time constant. All components except the reference oscillator and sweep circuits are integrated.</p> |
