CASCODE AMPLIFIER AND DIFFERENTIAL CASCODE VOLTAGE-CONTROLLED OSCILLATOR USING THE SAME

摘要

Provided is a differential cascode voltage-controlled oscillator that can reduce a phase noise by the use of a quality factor enhancement technique with negative conductance and can mitigate a ground-caused noise effect by the use of a cascode connection technique. The differential cascode voltage-controlled oscillator includes an AC signal generator, and first through fourth cascode amplifiers. The AC signal generator generates an AC signal with a certain frequency according to a control voltage. The first cascode amplifier is connected in a cascode configuration, and amplifies the AC signal to output the resulting signal to a first output terminal. The second cascode amplifier is connected in a cascode configuration and connected to the first cascode amplifier in a cross-coupled configuration, to amplify the AC signal to output the resulting signal to a second output terminal. The third cascode amplifier is connected in a cascode configuration to amplify the AC signal to output the resulting signal to the first output terminal. The fourth cascode amplifier is connected in a cascode configuration and connected to the third cascode amplifier in a cross-coupled configuration, to amplify the AC signal to output the resulting signal to the second output terminal. Herein, the first and second cascode amplifiers and the third and fourth cascode amplifiers are symmetrically connected to differentially amplify the AC signal.