Oscillators – Solid state active element oscillator – Transistors
Patent
1975-04-07
1976-08-03
Grimm, Siegfried H.
Oscillators
Solid state active element oscillator
Transistors
331 20, 331 34, 331177R, H03B 304, H03B 536
Patent
active
039732215
ABSTRACT:
A voltage controlled crystal oscillator is disclosed suitable to be included in a subcarrier regeneration stage for a color television receiver. The oscillator includes a novel phase shifting network in the feedback loop thereof for maintaining the oscillator in phase synchronism with a received NTSC reference burst signal. The phase shifting network comprises a first differential amplifier being adapted to receive a voltage oscillation signal having a 90.degree. phase lag with respect to the oscillation signal generated by the crystal. The differential outputs from the first differential amplifier are respectively connected to the common terminal of a second differential amplifier and to a phase shifting circuit. The output of the phase shifting circuit is a first current signal having a predetermined phase relation to the input signal applied thereto. The output of the second differential amplifier is a second current signal having a predetermined phase which is related to the first current signal, the magnitude of the second current signal being controlled by a phase detector output voltage control signal which is applied to the second differential amplifier. A summing circuit is provided which is responsive to the first and second phase related current signals for generating a feedback signal having a phase which may be varied over a predetermined range in response to the gain of the second differential amplifier being varied by the phase detector control voltage. The feedback signal from the summing circuit is applied to the crystal thereby ensuring the correct loop gain and phase shift is maintained for oscillation. Moreover, suppression of third overtone oscillation of the crystal is provided without a tuned circuit.
REFERENCES:
patent: 3691475 (1972-09-01), Mouri et al.
patent: 3763439 (1973-10-01), Peil
patent: 3806634 (1974-04-01), Abbott et al.
Bingham Michael D.
Grimm Siegfried H.
Motorola Inc.
Weiss Harry M.
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