| 摘要 |
A crystal oscillator apparatus is described that has a wide dynamic frequency range and that is capable of supporting a broad range of crystal types. The present invention reduces the unwanted side effects that are associated with the prior art crystal oscillator designs, such as the clipping of signals, the introduction of signal distortion and unwanted signal harmonics. The present invention reduces the total wasted loop gain of the oscillator while also reducing the amount of integrated circuit real estate required to implement the crystal oscillator. The crystal oscillator apparatus of the present invention preferably comprises a crystal resonator circuit, an inverting amplifier, a bias circuit, a reference circuit, and a peak detector circuit. The present invention takes advantage of Automatic Gain Control (AGC) design techniques. The gain of the present crystal oscillator is automatically regulated using a closed loop circuit design. The present invention advantageously utilizes a peak detector circuit in combination with a reference circuit. The peak detector compares a reference signal with an amplified and inverted oscillation signal produced by a crystal resonator, and generates a feedback signal as a result of the comparison. The feedback signal controls a bias circuit that, in turn, controls the amplified inverted oscillation signal. The preferred embodiment of the present invention preferably comprises MOSFETs, resistors and capacitors implemented on a single integrated circuit device. By implementing the present inventive crystal oscillator on a single integrated circuit device, the deleterious effects introduced by temperature variations are advantageously reduced or nullified.
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