Patent ID: 7821349
Filing Date: 2010-10-26
Classification: H03B,H03F

Abstract:
1. A differential cascode voltage-controlled oscillator comprising: an AC signal generator for generating an AC signal with a certain frequency according to a control voltage; a first cascode amplifier, provided in a cascode configuration, for amplifying the AC signal to output the resulting signal to a first output terminal; a second cascode amplifier, provided in a cascode configuration and connected to the first cascode amplifier in a cross-coupled configuration, for amplifying the AC signal to output the resulting signal to a second output terminal; a third cascode amplifier, provided in a cascode configuration, for amplifying the AC signal to output the resulting signal to the first output terminal; and a fourth cascode amplifier, provided in a cascode configuration and connected to the third cascode amplifier in a cross-coupled configuration, for amplifying the AC signal to output the resulting signal to the second output terminal, wherein the first and second cascode amplifiers and the third and fourth cascode amplifiers are symmetrically connected to thereby differentially amplify the AC signal, wherein the first cascode amplifier comprises: a first NMOS transistor having a gate receiving a DC voltage, a drain connected commonly to the first output terminal and the AC signal generator, and a source; a second NMOS transistor having a gate receiving an AC signal fed back from the second output terminal, a drain connected to the source of the first NMOS transistor, and a source connected to a ground terminal; a first capacitor connected between the drain and source of the first NMOS transistor; and a second capacitor connected between the gate and source of the first NMOS transistor.