Patent ID: 8120439

Claim:
A fast start-up crystal oscillator comprising: a gain stage with negative resistance; a crystal in a feedback loop of the gain stage, the crystal including a shunt capacitance; and a buffer operatively coupled to an input of the gain stage to isolate the gain stage from the shunt capacitance and to effectively increase the negative resistance of the gain stage, wherein the buffer operative for facilitating fast start-up and is selectively disabled when a threshold is reached; an oscillation detection and control circuit for decoupling the buffer in response to an amplitude of an oscillation signal exceeding a threshold value; a biasing resistor coupled in parallel with the gain stage for biasing the gain stage; and at least one load capacitor, wherein the oscillation detection and control circuit comprises: a high-pass filter; a hysteresis buffer operatively coupled to an output of the high-pass filter, the hysteresis buffer switches a digital value in response to the amplitude of the oscillation signal; and a latch operatively coupled to an output of the hysteresis buffer, the latch generates an enable signal in response to the digital value.