초록 ▼

A CMOS data clock oscillator circuit is disclosed which provides a simple, inexpensive, high-specification oscillator with an accurate duty cycle. The data clock oscillator 100 includes an oscillator stage 121 providing an AC output signal having an average DC value determined by an applied bias vol

A CMOS data clock oscillator circuit is disclosed which provides a simple, inexpensive, high-specification oscillator with an accurate duty cycle. The data clock oscillator 100 includes an oscillator stage 121 providing an AC output signal having an average DC value determined by an applied bias voltage, a limiting stage 124 having MOSFETs 102 and 103 configured to form a back-to-back limiter network to limit the amplitude of the AC output signal, a CMOS biasing stage 122 including complementary MOSFETs 104 and 105 configured to form an active resistor voltage divider network providing the bias voltage for the oscillator stage, and a CMOS buffer stage 123 including complementary MOSFETs 106 and 107 configured to form an inverting amplifier network having a predefined input switching threshold. Buffer stage MOSFETs 106 and 107 have conduction types, geometries, and device parameters matched to those of bias stage MOSFETs 104 and 105, respectively. In this way the inverter network input switching threshold tracks the bias voltage over changes in temperature, supply voltage, and manufacturing process tolerances. The instant invention is particularly well adapted for use as a data clock oscillator in microprocessor applications.

대표청구항 ▼

A crystal oscillator comprising: oscillator means for generating an AC output signal, said oscillator means including tank circuit means for resonating at a predetermined operating frequency, and including feedback amplifier means for providing regenerative feedback to said tank circuit means to sus

A crystal oscillator comprising: oscillator means for generating an AC output signal, said oscillator means including tank circuit means for resonating at a predetermined operating frequency, and including feedback amplifier means for providing regenerative feedback to said tank circuit means to sustain oscillation, said oscillator means further including input means for accepting a bias signal and output means for providing said AC output signal having a first duty cycle and having an average DC value determined by said bias signal; buffer means for amplifying said AC output signal, said buffer means including input means, coupled to said oscillator output means, for accepting said AC output signal, said buffer input means having a predefined switching threshold, said buffer means further including output means for providing a crystal oscillator output signal having a second duty cycle determined by said first duty cycle, said AC output signal average DC value, and said predefined switching threshold; biasing means, coupled to said oscillator input means, for providing said bias signal, said biasing means adapted to track device parameter variations of said buffer means and adapted to vary said bias signal such that said average DC value of said AC output signal follows said predefined switching threshold over changes in temperature, supply voltage, and manufacturing processes, thereby providing a crystal oscillator output signal exhibiting a precise duty cycle.