The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Oct. 29, 1991
Filed:
Jan. 17, 1991
Richard R Rasmussen, Fremont, CA (US);
National Semiconductor Corporation, Santa Clara, CA (US);
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.