High frequency CMOS VCO with gain constant and duty cycle compensation
First Claim
1. A voltage controlled oscillator circuit comprising:
- (a) multi-stage ring oscillator means that includes a plurality of series-connected inverter stages comprising N-channel and P-channel transistors, the ring oscillator means responsive to a control current signal for controlling the frequency of oscillation of the ring oscillator means; and
(b) voltage-to-current converter means for converting a tuning voltage input signal to a corresponding output signal that is independent of the channel strength of the N-channel and P-channel transistors;
(c) process compensation means responsive to the tuning voltage input signal for providing a current dump output signal corresponding to the channel strength of the P-channel and N-channel transistors; and
(d) trip-point compensation means responsive to the output signal and the current dump output signal to provide a net ring current signal as the control current signal to the ring oscillator means, the net ring current signal representing the difference between the output signal and the current dump output signal and responding to the balance between the output buffer'"'"'s input threshold and a ring inverter dummy stage.
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Abstract
The present invention provides a high frequency CMOS voltage controlled oscillator circuit with gain constant and duty cycle compensation. The voltage controlled oscillator circuit includes a multi-stage ring oscillator that includes a plurality of series-connected inverter stages comprising N-channel and P-channel transistors. The ring oscillator responds to a control current signal for controlling the frequency of oscillation of the ring oscillator. A voltage-to-current converter converts a tuning voltage input signal to a corresponding output current signal that is independent of the channel strength of the N-channel and P-channel transistors. Process compensation circuitry responds to the tuning voltage input signal to provide a current dump output signal corresponding to the channel strength of the P-channel and N-channel transistors. Trip-point compensation circuit provides a net ring current signal as the current control signal to the ring oscillator. The net ring current signal represents the difference between the output current signal and the current dump output signal and responds to the balance between the output buffer trip point and a ring oscillator dummy stage.
114 Citations
4 Claims
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1. A voltage controlled oscillator circuit comprising:
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(a) multi-stage ring oscillator means that includes a plurality of series-connected inverter stages comprising N-channel and P-channel transistors, the ring oscillator means responsive to a control current signal for controlling the frequency of oscillation of the ring oscillator means; and (b) voltage-to-current converter means for converting a tuning voltage input signal to a corresponding output signal that is independent of the channel strength of the N-channel and P-channel transistors; (c) process compensation means responsive to the tuning voltage input signal for providing a current dump output signal corresponding to the channel strength of the P-channel and N-channel transistors; and (d) trip-point compensation means responsive to the output signal and the current dump output signal to provide a net ring current signal as the control current signal to the ring oscillator means, the net ring current signal representing the difference between the output signal and the current dump output signal and responding to the balance between the output buffer'"'"'s input threshold and a ring inverter dummy stage. - View Dependent Claims (2, 3, 4)
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Specification