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:
Apr. 25, 1989
Filed:
Aug. 26, 1987
Edward F Culican, Hyde Park, NY (US);
John D Davis, Beacon, NY (US);
Martin E Powell, Poughkeepsie, NY (US);
Philip E Pritzlaff, Jr, Highland, NY (US);
International Business Machines Corporation, Armonk, NY (US);
Abstract
An oscillator with noise rejection which may be used in a gate array in a semiconductor chip including a first amplifier circuit, a circuit, for connecting an external feedback element (crystal) across the input and inverting output of the first amplifier circuit for generating and amplifying a sine wave, and a circuit connected to the inverting output of the first amplifier circuit for generating a square wave with the duty cycle thereof being proportional to the difference between the center of the voltage swing of the amplified sine wave and a reference voltage. In a preferred embodiment, the first amplifier circuit and the generating circuit each include a current switch. A voltage reference network is provided to set the reference voltage for the current switch in the generating circuit to the center of the voltage swing of the sine wave applied to that current switch. This results in a 50% duty cycle square wave for the output signal. A current source voltage reference is included for ensuring that each of the current switches and the voltage reference network drive approximately constant equal currents.