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:
Feb. 19, 2008
Filed:
Dec. 21, 2005
Boris Drakhlis, Mountain View, CA (US);
Wing Faat Liu, San Jose, CA (US);
Craig M. Taylor, Pleasanton, CA (US);
Tony Yeung, Milpitas, CA (US);
Boris Drakhlis, Mountain View, CA (US);
Wing Faat Liu, San Jose, CA (US);
Craig M. Taylor, Pleasanton, CA (US);
Tony Yeung, Milpitas, CA (US);
Pericom Semiconductor Corp., San Jose, CA (US);
Abstract
A crystal oscillator operates at the third overtone of the crystal's fundamental frequency. A value of a shunt resistor between the two phase-shift leg nodes is chosen so that the absolute value of the product gm×(Xc)×(Xc) is greater than the effective reactance of the crystal, where gm is the gain of the amplifier attached to the phase-shift legs, and Xcand Xcare the effective capacitive reactances of phase-shift legs at nodes Xand X. The third overtone is doubled by a multiplier and the final output filtered to remove the third overtone and select a frequency six times the fundamental frequency. A pair of Colpitts or Pierce amplifier half circuits is attached to the phase-shift leg nodes. The leg nodes can be capacitively isolated from Pierce-amplifier circuit nodes to improve start-up. Frequency doubling can be performed by summing currents from the two oscillator half circuits.