Voltage controlled variable capacitor and oscillator.

摘要

A voltage variable capacitor (VVC) having two terminals in a variable frequency crystal oscillator integrated into a common substrate with the oscillator circuitry and isolated therefrom. The VVC is constructed using the same processing steps as the oscillator circuitry and achieves low series resistance and wide capacitance variation by utilizing a substrate or epitaxial layer (body) (33) having a well (31) with a diffused region (34) therein. The region (34), of the same conductivity type as the well (31) and a first one of the two terminals, forms a rectangular ring in the well (31). Over the region (34) and insulated therefrom, a conductive layer (36) is deposited to provide a second one of the two terminals. Both terminals are electrically isolated from the body.