| 摘要 |
1360626 Transistor oscillators; automatic frequency control RCA CORPORATION 16 July 1971 [31 July 1970] 33530/71 Headings H3A and H3T A frequency controlled oscillator comprises a bistable circuit 72, 73 feeding an integrator 77, 78, 79, the output from the integrator being fed back to provide set and reset signals for the bi-stable via a threshold arrangement 71 which provides a reset signal when the integrator output level is equal to a reference level, and a set signal when the integrator output is equal to the frequency control voltage level. When capacitor 77 is discharged, transistor 71 is off, and cross-coupled transistors 72, 73 are on. When capacitor 77 has charged to a first predetermined threshold, transistor 77 conducts and transistors 72, 73 turn off. Capacitor 77 now discharges to a lower threshold at which 71 turns off and 72, 73 turn on. The turn on point of 72 is varied by a transistor 74 to which a control voltage is applied. The arrangement is used in a television timebase synchronizing, the control signal being derived from a phase comparator 46, 48 which compares the received sync. signal and the oscillator signal. |
