Crystal oscillation circuit
AssigneeNihon Dempa Kogya Co., Ltd.
InventorTakeo Oita
Life of this patent
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Abstract
A crystal oscillation circuit can correctly suppress the resonance of a B mode, thereby correctly excite the resonance of a C mode. Since the crystal oscillation circuit uses a quartz oscillator of an SC cut or an IC cut, the B mode (unnecessary mode) frequency is close to the C mode (main mode) frequency. Therefore, a C mode resonance circuit (main mode resonance circuit) for passing a C mode frequency and a trap circuit for suppressing the oscillation at an unnecessary mode frequency are provided in the feedback loop of the crystal oscillation circuit.
Claims7
A crystal oscillation circuit using a quartz oscillator in which an unnecessary mode frequency is close to a main mode frequency in a crystal cutting method, comprising:
- a main mode resonance circuit for passing the main mode frequency, and a trap circuit for suppressing the oscillation at the unnecessary mode frequency in a feedback loop of the crystal oscillation circuit;
- and
- a trap circuit having an unnecessary mode resonance circuit for suppressing the oscillation at the unnecessary mode frequency, in which the unnecessary mode resonance circuit is serially connected to a resistance device for adjusting an amount of trap in the unnecessary mode.
A colpitts crystal oscillation circuit having a quartz oscillator in which a main mode frequency is close to an unnecessary frequency using a crystal cutting method, and an amplification circuit, comprising:
- a main mode serial resonance circuit comprising an inductance device and a capacitance device in a feedback loop of the crystal oscillation circuit;
- and an unnecessary mode serial resonance circuit comprising an inductance device, a capacitance device, and a resistance device, wherein
- a serial resonance frequency of the main mode serial resonance circuit is set close to an oscillation frequency, and a serial resonance frequency of the unnecessary mode serial resonance circuit is set close to an unnecessary mode frequency, thereby suppressing an oscillation frequency in the unnecessary mode by a resistance value of the resistance device.
A colpitts crystal oscillation circuit having a quartz oscillator X1 and a transistor amplifier Tr1 in which the quartz oscillator X1 has at least, in series, a capacitor C1, capacitors C2 and C3 as divided capacities, and a resistance R3 as a feedback resistance connected between an emitter of the transistor amplifier Tr1 and the ground, wherein:
- in a feedback loop, an unnecessary mode serial resonance circuit is constituted by a series of a coil L2, a capacitor C5, and a resistance R4 and connected between the emitter of the transistor amplifier Tr1 and the ground;
- a main mode serial resonance circuit is constituted by serially connecting a coil L1 and a capacitor C4 and inserted between connection points of the emitter and the divided capacity capacitors C2 and C3;
- the unnecessary mode frequency of the unnecessary mode serial resonance circuit is set close to the oscillation frequency, and the main mode frequency of the main mode serial resonance circuit is set close to the oscillation frequency, thereby suppressing oscillation at the unnecessary mode frequency.
Dependencies are inferred from the claim text.